Explain how table salt has emergent properties.
Table salt (sodium chloride) is made up of sodium and chlorine. We are able to eat the compound, showing that it has different properties from those of a metal (sodium) and a poisonous gas (chlorine).
Is a trace element an essential element?
Yes, because an organism requires trace elements, even though only in small amounts
In humans, iron is a trace element required for the
proper functioning of hemoglobin, the molecule that
carries oxygen in red blood cells. What might be the
effects of an iron deficiency?
A person with an iron deficiency will probably show fatigue and other effects of a low oxygen level in the blood. (The condition is called anemia and can also result from too
few red blood cells or abnormal hemoglobin.)
Review the discussion of natural selection in Chapter 1 (pp. 14-16) and explain how natural selection might have played a role in the evolution
of species that are tolerant of serpentine soils.
Variant ancestral plants that could tolerate the toxic elements could grow and reproduce in serpentine soils. (Plants that were well adapted to nonserpentine soils would not be expected to survive in serpentine areas.) The offspring of the variants would also vary, with those most capable of thriving under serpentine conditions growing best and reproducing most. Over many generations, this probably led to the serpentineadapted species we see today.
A subatomic particle having no electrical charge (electrically neutral), with a mass of about 1.7 1024 g, found in the nucleus of an atom.
A subatomic particle with a single positive electrical charge, with a mass of about 1.7 1024 g, found in the nucleus
of an atom.
A subatomic particle with a single negative electrical charge and a mass about 1/2,000 that of a neutron or proton. One or more electrons move around the nucleus of an atom.
A measure of mass for atoms and subatomic particles; the same as the atomic mass unit, or amu.
One of several atomic forms of an element, each with the same number of protons but a different number of neutrons,
thus differing in atomic mass.
The capacity to cause change, especially to do work (to move matter against an opposing force).
An energy level of electrons at a characteristic average distance from the nucleus of an atom.
The outermost energy shell of an atom, containing the valence electrons involved in the chemical reactions of that atom.
A nitrogen atom has 7 protons, and the most common isotope of nitrogen has 7 neutrons. A radioactive isotope of nitrogen has 8 neutrons. Write the atomic number and mass number of this radioactive nitrogen as a chemical symbol with a subscript and superscript.
How many electrons does fluorine have? How many
electron shells? Name the orbitals that are occupied.
How many electrons are needed to fill the valence
9 electrons; two electron shells; 1s, 2s, 2p (three orbitals); 1 electron
is needed to fill the valence shell.
if two or more elements are in the same row, what do they have in common? If two or more elements are in the same column, what do they have in common?
The elements in a row all have the same number of electron shells. In a column, all the elements have the same number
of electrons in their valence shells.
An attraction between two atoms, resulting from a sharing of outer-shell electrons or the presence of opposite charges
on the atoms. The bonded atoms gain complete outer electron shells.
nonpolar covalent bond
A type of covalent bond in which electrons are shared equally between two atoms of similar electronegativity.
polar covalent bond
A covalent bond between atoms that differ in electronegativity. The shared electrons are pulled closer to the more
electronegative atom, making it slightly negative and the other atom slightly positive.
van der waals
A weak attractive force between atoms or nonpolar molecules caused by an instantaneous dipole moment of one atom or molecule that induces a similar temporary dipole moment in adjacent atoms or molecules.
A type of weak chemical bond that is formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule or in another region of
the same molecule.
Why does the structure H-C=C-H fail to make
Each carbon atom has only three covalent bonds instead of the required four.
What holds the atoms together in a crystal of magnesium
The attraction between oppositely charged ions, forming ionic bonds
If you were a pharmaceutical researcher,
why would you want to learn the three-dimensional
shapes of naturally occurring signaling molecules?
If you could synthesize molecules that mimic these shapes, you might be able to treat diseases or conditions caused by the inability of affected individuals to synthesize such molecules.
In a chemical reaction, the state in which the rate of the forward reaction equals the rate of the reverse reaction, so
that the relative concentrations of the reactants and products do not change with time.
Consider the reaction between hydrogen and oxygen that forms water, shown with ball-and-stick models on page 42. Study Figure 2.12 and draw the Lewis dot structures representing this reaction.
Which type of chemical reaction occurs faster at equilibrium,
the formation of products from reactants or
reactants from products?
At equilibrium, the forward and reverse reactions occur at the same rate.
Write an equation that uses the products
of photosynthesis as reactants and the reactants of
photosynthesis as products. Add energy as another
product. This new equation describes a process that
occurs in your cells. Describe this equation in words.
How does this equation relate to breathing?
C6H12O6 6 O2 S 6 CO2 6 H2O Energy. Glucose and oxygen react to form carbon dioxide and water, releasing energy. We breathe in oxygen because we need it for this reaction to occur, and we breathe out carbon dioxide because
it is a by-product of this reaction.
In the term trace element, the adjective trace means that
a. the element is required in very small amounts.
b. the element can be used as a label to trace atoms through
an organism's metabolism.
c. the element is very rare on Earth.
d. the element enhances health but is not essential for the organism's
e. the element passes rapidly through the organism.
a. the element is required in very small amounts.
In what way does the need for iodine or iron in your diet differ
from your need for calcium or phosphorus?
Iodine (part of a thyroid hormone) and iron (part of hemoglobin in blood) are both trace elements, required in minute quantities. Calcium and phosphorus (components
of bones and teeth) are needed by the body in much greater quantities.
Draw the electron distribution diagrams for neon
(10Ne) and argon (18Ar). Use these diagrams to explain why these
elements are chemically unreactive.
Both neon and argon have completed valence shells, containing 8 electrons. They do not have unpaired electrons that could participate in chemical bonds.
In terms of electron sharing between atoms, compare nonpolar
covalent bonds, polar covalent bonds, and the formation of ions.
Electrons are shared equally between the two atoms in a nonpolar covalent bond. In a polar covalent bond, the electrons are drawn closer to the more electronegative
atom. In the formation of ions, an electron is completely transferred from one atom to a much more electronegative atom.
What would happen to the concentration of products if more
reactants were added to a reaction that was in chemical equilibrium?
How would this addition affect the equilibrium?
The concentration of products
would increase as the added reactants were converted to products. Eventually, an
equilibrium would again be reached in which the forward and reverse reactions
were proceeding at the same rate and the relative concentrations of reactants and
products returned to where they were before the addition of more reactants
Compared with 31P, the radioactive isotope 32P has
a. a different atomic number. d. one more electron.
b. a different charge. e. one more neutron.
c. one more proton.
The reactivity of an atom arises from
a. the average distance of the outermost electron shell from
b. the existence of unpaired electrons in the valence shell.
c. the sum of the potential energies of all the electron shells.
d. the potential energy of the valence shell.
e. the energy difference between the s and p orbitals.
Which statement is true of all atoms that are anions?
a. The atom has more electrons than protons.
b. The atom has more protons than electrons.
c. The atom has fewer protons than does a neutral atom of
the same element.
d. The atom has more neutrons than protons.
e. The net charge is 1.
Which of the following statements correctly describes any
chemical reaction that has reached equilibrium?
a. The concentrations of products and reactants are equal.
b. The reaction is now irreversible.
c. Both forward and reverse reactions have halted.
d. The rates of the forward and reverse reactions are equal.
e. No reactants remain.
We can represent atoms by listing the number of protons,
neutrons, and electrons—for example, 2p, 2n0, 2e for helium.
Which of the following represents the 18O isotope of
a. 6p, 8n0, 6e d. 7p, 2n0, 9e
b. 8p, 10n0, 8e e. 10p, 8n0, 9e
c. 9p, 9n0, 9e
The atomic number of sulfur is 16. Sulfur combines with hydrogen
by covalent bonding to form a compound, hydrogen
sulfide. Based on the number of valence electrons in a sulfur
atom, predict the molecular formula of the compound.
a. HS b. HS2 c. H2S d. H3S2 e. H4S
What coefficients must be placed in the following blanks so
that all atoms are accounted for in the products?
C6H12O6 S _____ C2H6O _____ CO2
a. 1; 2 b. 3; 1 c. 1; 3 d. 1; 1 e. 2; 2
polar covalent bonds
A covalent bond between atoms that differ in electronegativity. The shared electrons are pulled closer to the more electronegative atom, making it slightly negative
and the other atom slightly positive.
What is electronegativity, and how does it affect interactions between water molecules?
Electronegativity is the attraction of an atom for the electrons of a covalent bond. Because oxygen is more electronegative than hydrogen, the oxygen atom in H2O pulls electrons toward itself, resulting in a partial negative charge on the
oxygen atom and partial positive charges on the hydrogen atoms. Atoms in neighboring water molecules with opposite partial charges are attracted to each other, forming a hydrogen bond.
What would be the effect on the properties of the water molecule if oxygen and hydrogen had equal electronegativity?
The covalent bonds of water molecules would not be polar, and water molecules would not form hydrogen bonds with each other.
The clinging of one substance to another, such as water to plant cell walls by means of hydrogen bonds.
A measure of how difficult it is to stretch or break the surface of a liquid. Water has a high surface tension because of the
hydrogen bonding of surface molecules.
A muscular pump that uses metabolic energy to elevate the hydrostatic pressure of the circulatory fluid (blood or hemolymph). The fluid then flows down a pressure gradient
through the body and eventually returns to the heart.
is a measure of heat intensity that represents the average kinetic energy of the molecules, regardless of volume.
Note: heat passes from the warmer to the cooler object until the two are the same temperature.
A temperature scale (°C) equal to 5/9(°F - 32) that measures the freezing point of water at 0°C and the boiling point of water at 100°C.
A thousand calories; the amount of heat energy required to raise the temperature of 1 kg of water by 1°C.
The amount of heat that must be absorbed or lost for 1 g of a substance to change its temperature by 1°C.
heat of vaporization
is the quantity of heat of liquid must absorb for 1g of it to be converted from the liquid to the gaseous state
The process in which the surface of an object becomes cooler during evaporation, a result of the molecules with the
greatest kinetic energy changing from the liquid to the gaseous state.
A mixture made up of a liquid and particles
that (because of their large size) remain
suspended rather than dissolved in that liquid.
Decreasing pH of ocean waters due to absorption of excess atmospheric CO2 from the burning of fossil fuels.
Describe how properties of water contribute to the
upward movement of water in a tree.
Hydrogen bonds hold neighboring water molecules together. This cohesion
helps the chain of water molecules move upward against gravity in waterconducting
cells as water evaporates from the leaves. Adhesion between water
molecules and the walls of the water-conducting cells also helps counter gravity.
Explain the saying "It's not the heat; it's the
High humidity hampers cooling by suppressing the evaporation of sweat.
How can the freezing of water crack boulders?
As water freezes, it expands because water molecules move farther apart in forming ice crystals. When there is water in a crevice of a boulder, expansion due to freezing may crack the boulder.
The concentration of the appetite-regulating hormone
ghrelin is about 1.3 1010M in a fasting person. How
many molecules of ghrelin are in 1 L of blood?
A liter of blood would contain 7.8 1013
molecules of ghrelin (1.3 1010 moles per liter 6.02 1023 molecules per mole).
A water strider (which can walk on water)
has legs that are coated with a hydrophobic substance.
What might be the benefit? What would
happen if the substance were hydrophilic?
The hydrophobic substance repels water, perhaps helping to keep the ends of the legs from becoming coated with water and breaking through the surface. If the legs were coated with a hydrophilic substance, water would be drawn up them, possibly making it more difficult for the water strider to walk on water.
Compared with a basic solution at pH 9, the same
volume of an acidic solution at pH 4 has ____ times
as many hydrogen ions (H).
105, or 100,000
HCl is a strong acid that dissociates in water:
HCl S H Cl. What is the pH of 0.01 M HCl?
H] 0.01 M 102M, so pH 2
Acetic acid (CH3COOH) can be a buffer, similar to
carbonic acid. Write the dissociation reaction, identifying
the acid, base, H acceptor, and H donor.
CH3COOH S CH3COO H. CH3COOH is the acid (the H donor), and CH3COO is the base (the H acceptor).
Given a liter of pure water and a liter solution
of acetic acid, what would happen to the pH if you
added 0.01 mol of a strong acid to each? Use the reaction equation from question 3 to explain the result.
The pH of the water should decrease from 7 to about
2; the pH of the acetic acid solution will decrease only a small amount, because
the reaction shown for question 3 will shift to the left, with CH3COO accepting
the influx of H and becoming CH3COOH molecules.
Describe how different types of solutes dissolve in water. Explain
the difference between a solution and a colloid.
Ions dissolve in water when polar water molecules form a hydration shell around them. Polar molecules dissolve as water molecules form hydrogen bonds with them and surround them. Solutions are homogeneous mixtures of solute and solvent. Colloids form when particles that are too large to dissolve remain suspended in a liquid.
Explain how increasing amounts of CO2 dissolving in the ocean
leads to ocean acidification. How does this change in pH affect
carbonate ion concentration and the rate of calcification?
CO2 reacts with H2O to form carbonic acid (H2CO3),
which dissociates into H and bicarbonate (HCO3
). Although the carbonic
acid-bicarbonate reaction is a buffering system, adding CO2 drives the reaction to
the right, releasing more H and lowering pH. The excess protons combine with
2 to form bicarbonate, lowering the concentration of carbonate available for
the formation of calcium carbonate (calcification) by corals.
Many mammals control their body temperature by sweating.
Which property of water is most directly responsible for the
ability of sweat to lower body temperature?
a. water's change in density when it condenses
b. water's ability to dissolve molecules in the air
c. the release of heat by the formation of hydrogen bonds
d. the absorption of heat by the breaking of hydrogen bonds
e. water's high surface tension
The bonds that are broken when water vaporizes are
a. ionic bonds.
b. hydrogen bonds between water molecules.
c. covalent bonds between atoms within water molecules.
d. polar covalent bonds.
e. nonpolar covalent bonds.
Which of the following is a hydrophobic material?
a. paper d. sugar
b. table salt e. pasta
We can be sure that a mole of table sugar and a mole of
vitamin C are equal in their
a. mass in daltons. d. number of atoms.
b. mass in grams. e. number of molecules.
Measurements show that the pH of a particular lake is 4.0.
What is the hydrogen ion concentration of the lake?
a. 4.0 M b. 1010 M c. 104 M d. 104 M e. 4%
What is the hydroxide ion concentration of the lake described
in question 5?
a. 1010 M b. 104 M c. 107 M d. 1014M e. 10 M
A slice of pizza has 500 kcal. If we could burn the pizza and
use all the heat to warm a 50-L container of cold water, what
would be the approximate increase in the temperature of the
water? (Note: A liter of cold water weighs about 1 kg.)
a. 50°C b. 5°C c. 1°C d. 100°C e. 10°C
How many grams of acetic acid (C2H4O2) would you use to
make 10 L of a 0.1 M aqueous solution of acetic acid? (Note:
The atomic masses, in daltons, are approximately 12 for
carbon, 1 for hydrogen, and 16 for oxygen.)
Draw the hydration shells that form around a
potassium ion and a chloride ion when potassium chloride (KCl) dissolves in water. Label the positive, negative, and partial charges on the atoms.
What do global warming (see
Chapter 1, p. 6) and ocean acidification have in common?
Both global warming and ocean acidification are caused by increasing levels of carbon dioxide in the atmosphere, the result of burning fossil fuels.
In agricultural areas, farmers pay close attention to the weather forecast. Right before a predicted overnight freeze, farmers spray water on crops to protect the plants. Use the properties of water to explain how this method works. Be sure to mention
why hydrogen bonds are responsible for this phenomenon.
Due to intermolecular hydrogen bonds, water has a high specific heat (the amount of heat required to increase the temperature of water by 1°C). When water is heated, much of the heat is absorbed in breaking hydrogen bonds before the water molecules increase their motion and the temperature increases. Conversely, when water is cooled, many H bonds are formed, which releases a significant
amount of heat. This release of heat can provide some protection against freezing of the plants' leaves, thus protecting the cells from damage.
the view that physical and chemical laws govern all natural phenomena, including the processes of life
In 1953, Stanley Miller, a graduate student of Harold Urey's at the University of Chicago, helped bring the
abiotic (nonliving) synthesis of organic compounds into the context of evolution. From his results, Miller concluded that complex organic molecules could arise spontaneously under conditions thought to have existed on the early Earth. Miller also performed experiments designed to mimic volcanic
conditions, with roughly similar results.
One of several compounds
that have the same molecular formula but
differ in the covalent arrangements of their
One of several compounds that have the same molecular formula and covalent bonds between atoms but differ in the spatial arrangements of their atoms owing to the inflexibility of double bonds; formerly called a geometric isomer.
One of two compounds that are mirror images of each other
and that differ in shape due to the presence of an asymmetric carbon.
the chemical groups affect molecular function by being directly involved in chemical reactions
An adenine-containing nucleoside
triphosphate that releases free energy when its
phosphate bonds are hydrolyzed. This energy
is used to drive endergonic reactions in cells.
Why was Wöhler astonished to find he had made urea?
Prior to Wöhler's experiment, the prevailing view was that only living organisms could synthesize "organic" compounds. Wöhler made urea, an organic compound, without the involvement of living organisms.
When Miller tried his experiment without
the electrical discharge, no organic compounds
were found. What might explain this result?
The spark provided energy needed for the inorganic molecules in the atmosphere to react with each other.
Which molecules in Figure 4.5 are isomers? For each
pair, identify the type of isomer.
The forms of C4H10 in (b) are structural isomers, as are the butenes in (c).
Can propane (C3H8) form isomers?
No. There is not enough diversity
in the atoms. It can't form structural isomers because there is only one way
for three carbons to attach to each other (in a line). There are no double bonds,
so cis-trans isomers are not possible. Each carbon has at least two hydrogens attached
to it, so the molecule is symmetrical and cannot have enantiomers.
What does the term amino acid signify about the
structure of such a molecule?
It has both an amino group (—NH2), which makes it an amine, and a carboxyl
group (—COOH), which makes it a carboxylic acid.
What chemical change occurs to ATP when it reacts
with water and releases energy?
The ATP molecule loses a phosphate, becoming ADP.
Suppose you had an organic molecule
such as cysteine (see Figure 4.9, sulfhydryl group example),
and you chemically removed the —NH2
group and replaced it with —COOH. Draw the structural
formula for this molecule and speculate about
its chemical properties. Is the central carbon asymmetric
before the change? After?
A chemical group that can act as a base has been replaced
with a group that can act as an acid, increasing the acidic properties of the molecule. The shape of the molecule would also change, likely changing the molecules with which it can interact. The original cysteine molecule has an asymmetric
carbon in the center. After replacement of the amino group with a carboxyl group, this carbon is no longer asymmetric.
How did Stanley Miller's experiments extend the idea of mechanism
to the origin of life?
Miller showed that organic molecules could form under the physical and
chemical conditions estimated to have been present on early Earth. This abiotic
synthesis of organic molecules would have been a first step in the origin of life.
What type of isomers are acetone and
propanal? How many asymmetric carbons are present in acetic
acid, glycine, and glycerol phosphate? Can these three molecules
exist as forms that are enantiomers?
Acetone and propanal are structural isomers. Acetic acid and glycine have no asymmetric carbons, whereas glycerol phosphate has one. Therefore, glycerol phosphate can exist as forms that are enantiomers, but acetic acid and glycine cannot.
In what ways does a methyl group differ chemically from the
other six important chemical groups shown in Figure 4.9?
The methyl group is nonpolar and not reactive. The other
six groups are called functional groups. They are each hydrophilic, increasing
the solubility of organic compounds in water, and can participate in chemical
Which chemical group is most
likely to be responsible for an organic molecule behaving as a
Which of the following hydrocarbons has a double bond in
its carbon skeleton?
a. C3H8 b. C2H6 c. CH4 d. C2H4 e. C2H2
Which action could produce a carbonyl group?
a. the replacement of the —OH of a carboxyl group with
b. the addition of a thiol to a hydroxyl
c. the addition of a hydroxyl to a phosphate
d. the replacement of the nitrogen of an amine with oxygen
e. the addition of a sulfhydryl to a carboxyl
Some scientists think that life elsewhere in the
universe might be based on the element silicon, rather than on carbon, as on Earth. Look at the electron distribution diagram for silicon in Figure 2.9 and draw the Lewis dot structure for silicon. What properties does silicon share with carbon
that would make silicon-based life more likely than, say, neon-based life or aluminum-based life?
Si has 4 valence electrons, the same number as carbon. Therefore, silicon
would be able to form long chains, including branches, that could act as
skeletons for large molecules. It would clearly do this much better than
neon (with no valence electrons) or aluminum (with 3 valence electrons).
A giant molecule formed by the
joining of smaller molecules, usually by a
dehydration reaction. Polysaccharides,
proteins, and nucleic acids are macromolecules.
a long molecule consisting of many similar or identical building blocks linked by covalent bonds
A macromolecule serving as a catalyst, a chemical agent that increases the rate of a reaction without being consumed by the reaction. Most enzymes are proteins.
loss or removal of water molecule(s) form a chemical reaction. To form a polymer
A sugar (monosaccharide) or one of its dimers (disaccharides) or polymers (polysaccharides).
double sugars, consisting of two monosaccharides joined by a covalent bond. double sugar,
consisting of two monosaccharides joined by
a glycosidic linkage formed by a dehydration
generally have molecular formulas that are some multiple of CH20. Glucose (C6H12O6). The
simplest carbohydrate, active alone or serving
as a monomer for disaccharides and polysaccharides.
Also known as simple sugars,
monosaccharides have molecular formulas
that are generally some multiple of CH2O.
macromoleucles, polymers with a few hundred to a few thousand mono-saccharides joined by glycosidic linkages.
A storage polysaccharide in plants, consisting entirely of glucose monomers joined by α glycosidic linkages.
A structural polysaccharide
of plant cell walls, consisting of glucose. "insoluble fiber"
A structural polysaccharide, consisting of amino sugar monomers, found in many fungal cell walls and in the exoskeletons of all arthropods.
Any of a group of large biological molecules, including fats, phospholipids, and steroids, that mix poorly, if at all, with water.
A lipid consisting of three fatty acids linked to one glycerol molecule; also called a triacylglycerol or triglyceride.
A carboxylic acid with a long carbon chain. Fatty acids vary in length and in the number and location of double bonds; three fatty acids linked to a glycerol molecule form a fat molecule, also known as a triacylglycerol or triglyceride.
A lipid consisting of three fatty acids linked to one glycerol
molecule; also called a fat or triglyceride.
unsaturated fatty acid
A fatty acid that has
one or more double bonds between carbons in
the hydrocarbon tail. Such bonding reduces
the number of hydrogen atoms attached to the
saturated fatty acid
A fatty acid in which all carbons in the hydrocarbon tail are connected by single bonds, thus maximizing the number
of hydrogen atoms that are attached to the carbon skeleton.
An unsaturated fat, formed artificially during hydrogenation of oils, containing one or more trans double bonds.
A lipid made up of glycerol joined to two fatty acids and a phosphate group. The hydrocarbon chains of the fatty acids act as nonpolar, hydrophobic tails, while the rest of the molecule acts as a polar, hydrophilic head. Phospholipids form bilayers that function as biological membranes.
A type of lipid characterized by a carbon skeleton consisting of four fused rings with various chemical groups attached.
A steroid that forms an essential component of animal cell membranes and acts as a precursor molecule for the
synthesis of other biologically important steroids, such as many hormones.
A chemical agent that selectively increases the rate of a reaction without being consumed by the reaction.
A biologically functional molecule consisting of one or more polypeptides folded and coiled into a specific three-dimensional structure.
An organic molecule possessing both a carboxyl and an amino group. Amino acids serve as the monomers of
The covalent bond between the carboxyl group on one amino acid and the amino group on another, formed by a
The level of protein structure
referring to the specific linear sequence of
Regions of repetitive coiling or folding of the polypeptide backbone of a protein due to hydrogen bonding between constituents of the backbone (not the side chains).
A coiled region constituting one form of the secondary structure of proteins, arising from a specific pattern of hydrogen bonding between atoms of the polypeptide backbone (not the side chains).
One form of the secondary
structure of proteins in which the polypeptide
chain folds back and forth. Two regions of
the chain lie parallel to each other and are
held together by hydrogen bonds between
atoms of the polypeptide backbone (not the
The overall shape of a protein molecule due to interactions of amino acid side chains, including hydrophobic interactions,
ionic bonds, hydrogen bonds, and disulfide bridges.
A type of weak chemical interaction caused when molecules
that do not mix with water coalesce to exclude water.
A strong covalent bond formed
when the sulfur of one cysteine monomer bonds
to the sulfur of another cysteine monomer.
The particular shape of a complex, aggregate protein,
defined by the characteristic three-dimensional arrangement of its constituent subunits, each a polypeptide.
A glycoprotein in the extracellular matrix of animal cells that forms strong fibers, found extensively in connective tissue
and bone; the most abundant protein in the animal kingdom.
A recessively inherited human blood disorder in which a single nucleotide change in the -globin gene causes
hemoglobin to aggregate, changing red blood cell shape and causing multiple symptoms in afflicted individuals.
In proteins, a process in which a protein loses its native
shape due to the disruption of weak chemical bonds and interactions, thereby becoming biologically inactive; in DNA, the separation of the two strands of the double helix. Denaturation occurs under extreme (noncellular) conditions
of pH, salt concentration, or temperature.
A technique used to study the three-dimensional structure of molecules. It depends on the diffraction of an X-ray beam by
the individual atoms of a crystallized molecule.
A discrete unit of hereditary information
consisting of a specific nucleotide sequence in
DNA (or RNA, in some viruses).
A polymer (polynucleotide) consisting of many nucleotide
monomers; serves as a blueprint for proteins and, through the actions of proteins, for all cellular activities. The two types are DNA and RNA.
A double-stranded, helical nucleic acid molecule, consisting of nucleotide monomers with a deoxyribose sugar and the
nitrogenous bases adenine (A), cytosine (C), guanine (G), and thymine (T); capable of being replicated and determining the inherited structure of a cell's proteins.
A type of nucleic acid consisting of a polynucleotide
made up of nucleotide monomers with a ribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and uracil (U); usually single-stranded; functions in
protein synthesis, gene regulation, and as the genome of some viruses.
A polymer consisting of many nucleotide monomers in a
chain. The nucleotides can be those of DNA or RNA.
The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and one or more phosphate groups.
One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring. Cytosine (C),
thymine (T), and uracil (U) are pyrimidines.
One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring fused to a fivemembered ring. Adenine (A) and guanine (G)
What are the four main classes of large biological
molecules? Which class does not consist of polymers?
The four main classes are proteins, carbohydrates, lipids, and nucleic acids. Lipids
are not polymers.
How many molecules of water are needed to completely
hydrolyze a polymer that is ten monomers
Nine, with one water molecule required to hydrolyze each
connected pair of monomers
Suppose you eat a serving of fish. What reactions must occur for the amino acid monomers in the protein of the fish to be converted to new proteins in your body?
The amino acids in the fish protein must be released
in hydrolysis reactions and incorporated into other proteins in dehydration reactions
A dehydration reaction joins two glucose molecules
to form maltose. The formula for glucose is C6H12O6.
What is the formula for maltose?
After a cow is given antibiotics to treat an
infection, a vet gives the animal a drink of "gut culture"
containing various prokaryotes. Why is this
The antibiotic treatment is likely to have killed the
cellulose-digesting prokaryotes in the cow's stomach. The absence of these prokaryotes
would hamper the cow's ability to obtain energy from food and could lead to
weight loss and possibly death. Thus, prokaryotic species are reintroduced, in appropriate
combinations, in the gut culture given to treated cows.
Compare the structure of a fat (triglyceride) with that
of a phospholipid.
Both have a glycerol molecule attached to fatty acids. The glycerol of a fat has three fatty acids attached, whereas the glycerol of a phospholipid is attached to two fatty acids and one phosphate group.
Why are human sex hormones considered lipids?
Human sex hormones are steroids, a type of hydrophobic compound.
Suppose a membrane surrounded an oil
droplet, as it does in the cells of plant seeds. Describe
and explain the form it might take.
The oil droplet membrane could consist of a single layer of phospholipids rather than a bilayer, because an arrangement in which the hydrophobic tails of the membrane phospholipids were in contact with the hydrocarbon regions of the oil molecules would be more stable.
Why does a denatured protein no longer function
The function of a protein is a consequence of its specific shape, which is lost
when a protein becomes denatured.
What parts of a polypeptide participate in the bonds
that hold together secondary structure? Tertiary
Secondary structure involves hydrogen bonds between atoms of the polypeptide backbone. Tertiary structure involves interactions between atoms of the side chains of the amino acid subunits.
Where would you expect a polypeptide
region that is rich in the amino acids valine, leucine,
and isoleucine to be located in the folded polypeptide?
These are all nonpolar amino acids, so you would expect this region to be located in the interior of the folded polypeptide, where it would not contact the aqueous environment inside the cell.
In a DNA double helix, a region along one DNA strand has this sequence of nitrogenous bases: 5-TAGGCCT-3. Copy this sequence, and write down its complementary strand, clearly indicating the 5 and 3 ends of the complementary strand.
(a) Suppose a substitution occurred in one DNA strand of the double helix in question 2, resulting in
Copy these two strands, and circle and label the mismatched bases. (b) If the modified top strand is used by the cell to construct a complementary strand, what would that matching strand be?
Thy bottom would be T
What is the fundamental basis for the differences between carbohydrates,
proteins, and nucleic acids?
The polymers of carbohydrates, proteins, and nucleic acids are built from three different types of monomers: monosaccharides, amino acids, and nucleotides,
Compare the composition, structure, and function of
starch and cellulose. What role do starch and cellulose play in the human body?
Both starch and cellulose are polymers of glucose, but the
glucose monomers are in the α configuration in starch and the β configuration in cellulose.
The glycosidic linkages thus have different geometries, giving the polymers different
shapes and thus different properties. Starch is an energy-storage compound in
plants; cellulose is a structural component of plant cell walls. Humans can hydrolyze
starch to provide energy but cannot hydrolyze cellulose. Cellulose aids in
the passage of food through the digestive tract.
Why are lipids not considered to be macromolecules or polymers?
Lipids are not polymers because they do not exist as a chain of linked monomers. They are not considered macromolecules because they do not reach the giant size of many polysaccharides, proteins, and nucleic acids.
Proteins are the most structurally and functionally diverse class of biological molecules. Explain the basis for this diversity.
A polypeptide, which may consist of hundreds of amino acids in a specific sequence (primary structure), has regions of coils and pleats (secondary structure), which are then folded into irregular contortions (tertiary structure) and may be noncovalently associated with other polypeptides (quaternary structure). The linear order of amino acids, with the varying properties of their side chains (R groups), determines what secondary and tertiary structures will form to produce a protein. The resulting unique three-dimensional
shapes of proteins are key to their specific and diverse functions.
What role does complementary
base pairing play in the
functions of nucleic acids?
The complementary base pairing of the two strands of DNA makes possible the precise replication of DNA every time a cell divides, ensuring that genetic information is faithfully transmitted. In some types of RNA, complementary base pairing enables RNA molecules to assume specific three-dimensional shapes that facilitate diverse
Which of the following categories includes all others in the list?
a. monosaccharide d. carbohydrate
b. disaccharide e. polysaccharide
The enzyme amylase can break glycosidic linkages between
glucose monomers only if the monomers are in the form.
Which of the following could amylase break down?
a. glycogen, starch, and amylopectin
b. glycogen and cellulose
c. cellulose and chitin
d. starch and chitin
e. starch, amylopectin, and cellulose
Which of the following statements concerning unsaturated
fats is true?
a. They are more common in animals than in plants.
b. They have double bonds in the carbon chains of their fatty
c. They generally solidify at room temperature.
d. They contain more hydrogen than do saturated fats having
the same number of carbon atoms.
e. They have fewer fatty acid molecules per fat molecule.
The structural level of a protein least affected by a disruption
in hydrogen bonding is the
a. primary level. d. quaternary level.
b. secondary level. e. All structural levels are
c. tertiary level equally affected.
Enzymes that break down DNA catalyze the hydrolysis of the
covalent bonds that join nucleotides together. What would
happen to DNA molecules treated with these enzymes?
a. The two strands of the double helix would separate.
b. The phosphodiester linkages of the polynucleotide backbone
would be broken.
c. The purines would be separated from the deoxyribose sugars.
d. The pyrimidines would be separated from the deoxyribose
e. All bases would be separated from the deoxyribose sugars.
The molecular formula for glucose is C6H12O6. What would
be the molecular formula for a polymer made by linking ten
glucose molecules together by dehydration reactions?
a. C60H120O60 d. C60H100O50
b. C6H12O6 e. C60H111O51
Which of the following pairs of base sequences could form a
short stretch of a normal double helix of DNA?
a. 5-purine-pyrimidine-purine-pyrimidine-3 with 3-purinepyrimidine-
b. 5-AGCT-3 with 5-TCGA-3
c. 5-GCGC-3 with 5-TATA-3
d. 5-ATGC-3 with 5-GCAT-3
e. All of these pairs are correct.
Construct a table that organizes the following terms, and label
the columns and rows.
phosphodiester linkages polypeptides monosaccharides
peptide bonds triacylglycerols nucleotides
glycosidic linkages polynucleotides amino acids
ester linkages polysaccharides fatty acids
Copy the polynucleotide strand in Figure 5.26a
and label the bases G, T, C, and T, starting from the 5 end.
Assuming this is a DNA polynucleotide, now draw the complementary
strand, using the same symbols for phosphates (circles),
sugars (pentagons), and bases. Label the bases. Draw
arrows showing the 5 → 3 direction of each strand. Use the arrows
to make sure the second strand is antiparallel to the first.
Hint: After you draw the first strand vertically, turn the paper
upside down; it is easier to draw the second strand from the 5
toward the 3 direction as you go from top to bottom.
An optical instrument
with lenses that refract (bend) visible light to
magnify images of specimens.
The clarity of the image; it is the minimum distance two points can be seperated and still be distinguished as two parts
takes cells apart and separates major organelles and other subceullular structures from one another
Note: Parkayotic Cell the DNA is concentrated in a regin that is not membrane-enclosed called the nucleoid
selective barrier that allows passage of enough oxygen, nutrients and waste to service the entire cell
Note: larger organisms do not generally have larger cless than smaller organisms; they imply have more celss.
long thin projections that increase surface area without an appreciable increase in volume
a netlike array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope
non-membrane bound structure composed of proteins and nucleic acids found within the nucleus. Ribosomal RNA (rRNA) is transcribed and assembled within the nucleolus.
complexes made of ribosomal RNA and protein, are the cellular components that carry out protein synthesis
includes the nuclear envelope, the endoplasmic reticulum, the golgi appartus, lysosomes, various kinds of vesicles and vacules and the plasmas membrane
a small bubble enclosed by lipid bilayer. Vesicles do many things. The membrane enclosing the vesicle is similar to that of the plasma membrane, and vesicles can fuse with the plasma membrane to release their contents outside of the cell. Vesicles can also fuse with other organelles within the cell. Because it is separated from the cytosol, the inside of the vesicle can be made to be different from the cytosolic environment. For this reason, vesicles are a basic tool used by the cell for organizing cellular substances. Vesicles are involved in metabolism, transport, buoyancy control, and enzyme storage. They can also act as chemical reaction chambers
these processes include synthesis of lipids, metabolism of carbohydrates, detoxification of drugs and poisons, and storage of calcium ions.
The Golgi apparatus consists of stacks of flattened sacs, or cisternae, which, unlike ER cisternae, are not physically connected. (The drawing is a cutaway view.) A Golgi stack receives and dispatches transport vesicles and the products they contain. A Golgi stack has a structural and functional directionality, with a cis face that receives vesicles containing ER products and a trans face that dispatches vesicles. The cisternal maturation model proposes that the Golgi cisternae themselves mature, moving from the cis to the trans face while carrying some proteins along. In addition, some vesicles recycle enzymes that had been carried forward in moving cisternae, transporting them "backward" to a less mature region where their functions are needed.
are cellular organelles that contain acid hydrolase enzymes that break down waste materials and cellular debris. These are non-specific. They can be described as the stomach of the cell. They are found in animal cells, while their existence in yeasts and plants are disputed. Some biologists say the same roles are performed by lytic vacuoles,, while others suggest there is strong evidence that lysosomes are indeed in some plant cells. Lysosomes digest excess or worn-out organelles, food particles, and engulf viruses or bacteria. The membrane around a lysosome allows the digestive enzymes to work at the 4.5 pH they require. Lysosomes fuse with vacuoles and dispense their enzymes into the vacuoles, digesting their contents. They are created by the addition of hydrolytic enzymes to early endosomes from the Golgi apparatus. The name lysosome derives from the Greek words lysis, to separate, and soma, body. They are frequently nicknamed "suicide-bags" or "suicide-sacs" by cell biologists due to their autolysis
saclike structures that store materials such as water, salts, proteins, and carbohydrates
A membranous sac formed by
phagocytosis of microorganisms or particles to
be used as food by the cell.
mitochondria) An organelle in eukaryotic
cells that serves as the site of cellular respiration;
uses oxygen to break down organic
molecules and synthesize ATP.
organelles that capture the energy from sunlight and convert it into chemical energy in a process called photosynthesis
The theory that mitochondria and plastids, including chloroplasts, originated as prokaryotic cells engulfed by an ancestral eukaryotic cell. The engulfed cell and its host cell then evolved into a single organism.
Infoldings of the inner membrane of a mitochondrion that houses the electon transport chain and the enzyme catalyzing the synthesis of ATP.
The compartment of the mitochondrion enclosed by the inner membrane and containing enzymes and substrates for the Krebs cycle.
A flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy.
The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
A microbody containing enzymes that transfer hydrogen from various substrates to oxygen, producing and then degrading hydrogen peroxide.
a microscopic network of actin filaments and microtubules in the cytoplasm of many living cells that gives the cell shape and coherence
A protein that interacts with cytoskeletal elements and other cell components, producing movement of the whole cell or parts of the cell.
hollow tubes of protein about 25 nanometers in diameter, support the cell and moves organelles within the cell
Threadlike proteins in the cell's cytoskeleton that are roughly twice as thick as microfilaments
Material present in the cytoplasm of all eukaryotic cells, important during cell division; the microtubule-organizing center.
One of two tiny structures located in the cytoplasm of animal cells near the nuclear envelope; play a role in cell division.
short structures projecting from a cell and containing bundles of microtubules that move a cell through its surroundings or move fluid over the cell's surface
A eukaryotic cell structure
consisting of a "9 0" arrangement of microtubule
triplets. The basal body may organize
the microtubule assembly of a cilium or
flagellum and is structurally very similar to
a large motor protein on the outer doublets of cilia and flagella that provides bending movement for microtubules; performs movements by conformational changes, which ATP causes with energy
A globular protein that links into chains, two of which twist helically about each other, forming microfilaments in muscle and other contractile elements in cells.
(1) The outer region of cytoplasm in a eukaryotic
cell, lying just under the plasma membrane,
that has a more gel-like consistency
than the inner regions due to the presence of
multiple microfilaments. (2) In plants, ground
tissue that is between the vascular tissue and
dermal tissue in a root or eudicot stem.
A protein present in muscle fibers that aids in contraction and makes up the majority of muscle fiber
large, rounded cytoplasmic extensions that function both in movement and feeding, false foot
A circular flow of cytoplasm, involving myosin and actin filaments, that speeds the distribution of materials within cells.
A protective layer external to the
plasma membrane in the cells of plants,
prokaryotes, fungi, and some protists.
Polysaccharides such as cellulose (in plants
and some protists), chitin (in fungi), and
peptidoglycan (in bacteria) are important
structural components of cell walls.
primary cell wall
In plants, a relatively thin
and flexible layer that surrounds the plasma
membrane of a young cell
in plants, a thin layer of adhesive extracellular material, primarily pectins, found between the primary walls of adjacent young cells.
secondary cell wall
In plant cells, a strong and
durable matrix that is often deposited in several
laminated layers around the plasma membrane
and provides protection and support.
extracellular matrix (ECM)
The meshwork surrounding animal cells, consisting of glycoproteins, polysaccharides, and proteoglycans
synthesized and secreted by the cells.
A glycoprotein in the extracellular matrix of animal cells that forms strong fibers, found extensively in connective tissue and bone; the most abundant protein in the animal kingdom.
A large molecule consisting of a small core protein with
many carbohydrate chains attached, found in the extracellular matrix of animal cells. A proteoglycan may consist of up to 95% carbohydrate.
in animal cells, a transmembrane receptor protein that interconnects the extracellular matrix and the cytoskeleton.
Open channels in the cell wall of a plant through which strands of cytosol connect from an adjacent cell.
A type of intercellular junction
between animal cells that prevents the leakage
of material through the space between cells.
Button-like plaques, present on two oppsing cell surfaces, that hold the cells together by means of protein filaments that span the intercellular space
Points that provide cytoplasmic channels from one cell to another with special membrane proteins. Also called communicating junctions.
How do stains used for light microscopy compare
with those used for electron microscopy?
Stains used for light microscopy are colored molecules that bind to cell components, affecting the light passing through, while stains used for electron microscopy involve heavy metals that affect the beams of electrons passing
Which type of microscope would you use
to study (a) the changes in shape of a living white blood cell and (b) the details of surface texture of a hair?
(a) Light microscope, (b) scanning electron microscope
What role do ribosomes play in carrying out genetic
Ribosomes in the cytoplasm translate the genetic message, carried from the DNA in the nucleus by mRNA, into a polypeptide chain.
Describe the molecular composition of nucleoli and
explain their function.
Nucleoli consist of DNA and the ribosomal RNA (rRNA) made according to its instructions, as well as proteins imported from the cytoplasm. Together, the rRNA and proteins are assembled into large and small ribosomal subunits. (These are exported through nuclear pores to the cytoplasm, where they will participate in polypeptide synthesis.)
As a cell begins the process of dividing, its chromatin becomes more and more condensed.
Does the number of chromosomes change during this process? Explain.
No. Each chromosome is present whether its chromatin is relatively diffuse (when the cell is not dividing) or condensed (when the cell is dividing).
Describe the structural and functional distinctions between rough and smooth ER.
The primary distinction between rough and smooth ER is the presence of bound ribosomes on the rough ER. Both types of ER make phospholipids, but membrane proteins and secretory proteins are all produced on the ribosomes of
the rough ER. The smooth ER also functions in detoxification, carbohydrate metabolism, and storage of calcium ions.
Describe how transport vesicles integrate the endomembrane system.
Transport vesicles move membranes and substances they enclose between other components of the endomembrane
Imagine a protein that functions in the ER but requires modification in the Golgi apparatus
before it can achieve that function. Describe the protein's path through the cell, starting with the mRNA molecule that specifies the protein.
The mRNA is synthesized in the nucleus and then passes out through a nuclear pore to be translated on a bound ribosome, attached to the rough ER. The protein is synthesized into the lumen of the ER and perhaps modified there.A transport vesicle carries the protein to the Golgi apparatus. After further modification in the Golgi, another transport vesicle carries it back to the ER, where it
will perform its cellular function.
Describe two common characteristics of chloroplasts and mitochondria. Consider both function and membrane structure.
Both organelles are involved in energy transformation, mitochondria in cellular respiration and chloroplasts in photosynthesis. They both have multiple membranes
that separate their interiors into compartments. In both organelles, the innermost membranes—cristae, or infoldings of the inner membrane, in mitochondria, and the thylakoid membranes in chloroplasts—have large surface areas with embedded enzymes that carry out their main functions.
Do plant cells have mitochondria? Explain.
Yes. Plant cells are able to make their own sugar by photosynthesis, but mitochondria in these eukaryotic cells are the organelles that are able to generate energy from sugars, a function required in all cells.
A classmate proposes that mitochondria
and chloroplasts should be classified in the endomembrane system. Argue against the proposal.
Mitochondria and chloroplasts are not derived from the ER, nor are they connected physically or via transport vesicles to
organelles of the endomembrane system. Mitochondria and chloroplasts are structurally quite different from vesicles derived from the ER, which are bounded by a single membrane.
Describe shared features of microtubule-based motion of flagella and microfilament-based muscle contraction.
Both systems of movement involve long filaments that are moved in relation to each other by motor proteins that grip, release, and grip again adjacent polymers.
How do cilia and flagella bend?
Dynein arms, powered by ATP, move neighboring doublets of microtubules relative to each other. Because they are anchored within the organelle and with respect to one another, the doublets bend instead of sliding past each
other. Synchronized bending of the nine microtubule doublets brings about bending of both structures.
Males afflicted with Kartagener's syndrome
are sterile because of immotile sperm, and they
tend to suffer from lung infections. This disorder has a genetic basis. Suggest what the underlying defect might be.
Such individuals have defects in the microtubulebased
movement of cilia and flagella. Thus, the sperm can't move because of malfunctioning or nonexistent flagella, and the airways are compromised because cilia that line the trachea malfunction or don't exist, and so mucus cannot be
cleared from the lungs.
In what way are the cells of plants and animals structurally different from single-celled eukaryotes?
The most obvious difference is the presence of direct cytoplasmic connections between cells of plants (plasmodesmata) and animals (gap junctions).
These connections result in the cytoplasm being continuous between adjacent cells.
If the plant cell wall or the animal extracellular
matrix were impermeable, what effect would
this have on cell function?
The cell would not be able to function properly and would probably soon die, as the cell wall or ECM must be permeable to allow the exchange of matter between the cell and its external environment. Molecules involved in energy production and use must be allowed entry, as well as those that provide information about the cell's environment. Other molecules, such as products synthesized by the cell for export and the by-products of cellular respiration, must be allowed to exit.
The polypeptide chain that makes up a tight junction weaves back and forth through the membrane four times, with two extracellular
loops, and one loop plus short C-terminal and Nterminal tails in the cytoplasm. Looking at Figure 5.16 (p. 79), what would you predict about the amino acid sequence of the tight-junction protein?
The parts of the protein that face aqueous
regions would be expected to have polar or charged (hydrophilic) amino acids, while the parts that go through the membrane would be expected to have nonpolar (hydrophobic) amino acids. You would predict polar or
charged amino acids at each end (tail), in the region of the cytoplasmic loop, and in the regions of the two extracellular loops. You would predict nonpolar amino acids in the four regions that go through the membrane between the tails and loops.
How do microscopy and biochemistry complement each other to reveal cell structure and function?
Both light and electron microscopy allow cells to be studied visually, thus helping us understand internal cellular structure and the arrangement of cell components. Cell fractionation techniques separate out different groups of cell components, which can then be analyzed biochemically to determine their
function. Performing microscopy on the same cell fraction helps to correlate the biochemical function of the cell with the cell component responsible.
Explain how the compartmental organization of a eukaryotic cell contributes to its biochemical functioning.
The separation of different functions in different organelles has several advantages. Reactants and enzymes can be concentrated in one area instead of spread throughout the cell. Reactions that require specific conditions, such as a lower pH, can be compartmentalized. And enzymes for specific reactions are often embedded in the membranes that enclose or partition an organelle.
Describe the relationship between the nucleus and
The nucleus contains the genetic material of the cell in the form of DNA, which codes for messenger RNA, which in turn provides instructions for the synthesis of proteins (including the proteins that make up part of the ribosomes). DNA also
codes for ribosomal RNA, which is combined with proteins in the nucleolus into the subunits of ribosomes. Within the cytoplasm, ribosomes join with mRNA to build polypeptides, using the genetic information in the mRNA.
Describe the key role played by transport vesicles in the endomembrane system.
Transport vesicles move proteins and membranes synthesized by the rough ER to the Golgi for further processing and then to the plasma membrane, lysosomes, or other locations in the cell, including back to the ER.
What is the endosymbiont theory?
According to the endosymbiont theory, mitochondria originated from an oxygen-using prokaryotic cell that was
engulfed by an ancestral eukaryotic cell. Over time, the host and endosymbiont evolved into a single organism. Chloroplasts originated when at least one of these eukaryotic cells containing mitochondria engulfed and then retained a
Describe the role of motor proteins inside the eukaryotic cell and in whole-cell movement.
Inside the cell, motor proteins interact with components
of the cytoskeleton to move cellular parts. Motor proteins may "walk" vesicles along microtubules. The movement of cytoplasm within a cell involves interactions of the motor protein myosin and microfilaments (actin filaments).
Whole cells can be moved by the rapid bending of flagella or cilia, which is caused by the motor-protein-powered sliding of microtubules within these structures. Cell movement can also occur when pseudopodia form at one end of a
cell (caused by actin polymerization into a filamentous network), followed by contraction of the cell toward that end; this is powered by interactions of microfilaments with myosin. Interactions of motor proteins and microfilaments in
muscle cells can propel whole organisms.
Compare the composition and functions of a plant cell wall and the extracellular matrix of an animal cell.
A plant cell wall is primarily composed of microfibrils of cellulose embedded in other polysaccharides and proteins.
The ECM of animal cells is primarily composed of collagen and other protein fibers, such as the glycoprotein fibronectins. These fibers are embedded in a network of carbohydrate-rich proteoglycans. A plant cell wall provides structural support for the cell and, collectively, for the plant body. In addition to giving support, the ECM of an animal cell
Which structure is not part of the endomembrane system?
a. nuclear envelope d. plasma membrane
b. chloroplast e. ER
c. Golgi apparatus
Which structure is common to plant and animal cells?
a. chloroplast d. mitochondrion
b. wall made of cellulose e. centriole
c. central vacuole
Which of the following is present in a prokaryotic cell?
a. mitochondrion d. chloroplast
b. ribosome e. ER
c. nuclear envelope
Which structure-function pair is mismatched?
a. nucleolus; production of ribosomal subunits
b. lysosome; intracellular digestion
c. ribosome; protein synthesis
d. Golgi; protein trafficking
e. microtubule; muscle contraction
Cyanide binds to at least one molecule involved in producing
ATP. If a cell is exposed to cyanide, most of the cyanide will be
found within the
a. mitochondria. d. lysosomes.
b. ribosomes. e. endoplasmic reticulum.
What is the most likely pathway taken by a newly synthesized
protein that will be secreted by a cell?
a. ER → Golgi → nucleus
b. Golgi → ER → lysosome
c. nucleus → ER → Golgi
d. ER → Golgi → vesicles that fuse with plasma membrane
e. ER → lysosomes → vesicles that fuse with plasma membrane
Which cell would be best for studying lysosomes?
a. muscle cell d. leaf cell of a plant
b. nerve cell e. bacterial cell
c. phagocytic white blood cell
the branch of biology concerned with the relations between organisms and their environment
the regions of the surface and atmosphere of the Earth (or other planet) where living organisms exist
An area containing several different
ecosystems linked by exchanges of energy,
materials, and organisms.
a system formed by the interaction of a community of organisms with their physical environment
The study of energy flow and the cycling of chemicals among the various biotic and abiotic factors in an ecosystem.
All the organisms that inhabit a particular area; an assemblage of populations of different species living close enough together for potential interaction.
The study of how interactions between species affect community structure and organization.
A group of individuals of the same species that live in the same area and interbreed, producing fertile offspring.
The study of populations in relation to their environment, including environmental influences on population density
and distribution, age structure, and variations in population size.
The branch of ecology concerned with the morphological, physiological, and behavioral ways in which individual organisms meet the challenges posed by their biotic and abiotic environments
Equatorial region between the Tropic of Cancer and the Tropic of Capricorn. It is characterized by generally warm or hot temperatures year-round, though much variation exists due to altitude and other factors. (370)
climate within a small area that differs significantly from the climate of the surrounding area
nonliving, physical features of the environment, including air, water, sunlight, soil, temperature, and climate
a broad, regional type of ecosystem characterized by distinctive climate and soil conditions and a distinctive kind of biological community adapted to those conditions.
natural or human-caused event that changes a biological community and usually removes organisms from it. Disturbances, such as fires and storms, play a pivotal role in
structuring many communities.
biome characterized by deep, nutrient-rich soil that supports many grass species
Northern coniferous forest
a terrestrial biome characterized by long, cold winters and dominated by cone-bearing trees
temperate broadleaf forest
a biome located throughout midlatitude regions where there is sufficient moisture to support the growth of large, broadleaf deciduous trees
the part of the ocean beneath the photic zone, where light does not penetrate sufficiently for photosynthesis to occur.
The portion of the ocean floor where light does not penetrate and where temperatures are cold and pressures intense.
bottom of an aquatic ecosystem; consists of sand and sediment and supports its own community of organisms
In water, a distinctive temperature transition zone that separates an upper layer that is mixed by wind (the epilimnion) and a colder, deep layer that is not mixed (the hypolimnion)
Ecosystems of several types in which vegetation is surrounded by stand water during part of the year
streams and rivers
frest water, flowing water, generally support different communiteis of organisms, at source usually cold low in nutrients and cles, warmer and murkier at the end
Prominent oceanic features composed of hard, limy skeletons produced by coral animals; usually formed along edges of shallow, submerged ocean banks or along shelves in warm, shallow, tropical seas
The movement of individuals or
gametes away from their parent location.
This movement sometimes expands the
geographic range of a population or species.
Explain how the sun's unequal heating of Earth's surface leads to the development of deserts around 30° north and south of the equator.
In the tropics, high temperatures evaporate water and cause warm, moist air to rise. The rising air cools and releases much of its water as rain over the tropics. The remaining
dry air descends at approximately 30° north and south, causing deserts to occur in those regions.
What are some of the differences in microclimate between an unplanted agricultural field and a nearby
stream corridor with trees?
The microclimate around the stream will be cooler, moister, and shadier than that around the unplanted agricultural field.
Changes in Earth's climate at the end
of the last ice age happened gradually, taking centuries to thousands of years. If the current global
warming happens very quickly, as predicted,
how may this rapid climate change affect the
ability of long-lived trees to evolve, compared
with annual plants, which have much shorter
Trees that require a long time to reach reproductive age are likely to evolve more slowly than annual plants in response to climate change, constraining the potential ability of such trees
to respond to rapid climate change.
you learned about the important differences between C3 and C4 plants. Focusing just on the effects of temperature, would you expect the global distribution of C4 plants to expand or contract as Earth becomes warmer? Why?
Plants with C4 photosynthesis are likely to expand
their range globally as Earth's climate warms. As described in Concept 10.4, C4 photosynthesis minimizes photorespiration and enhances sugar production, an advantage that is especially useful in warmer regions where C4 plants are found today.
what mainly differentiates temperate grassland from temperate broadleaf forest?
Temperate broadleaf forests have higher mean annual precipitation.
Identify the natural biome in which you live, and
summarize its abiotic and biotic characteristics. Do
these reflect your actual surroundings? Explain.
Answers will vary by location but should be based on the information and maps in Figure 52.12. How much your local area has been altered from its natural state will influence
how much it reflects the expected characteristics of your biome, particularly the expected plants and animals.
If global warming increases average temperatures
on Earth by 4°C in this century, predict which biome is most likely to replace tundra in some locations as a result. Explain your answer.
Northern coniferous forest is likely to replace tundra along the boundary between these biomes. To see why, note that northern coniferous forest is adjacent to tundra throughout North America, northern Europe, and Asia (see Figure 52.9) and that the temperature range for northern coniferous
forest is just above that for tundra (see Figure 52.10).
Why are phytoplankton, and not benthic algae or
rooted aquatic plants, the dominant photosynthetic
organisms of the oceanic pelagic zone?
1. In the oceanic pelagic zone, the ocean bottom lies below the photic zone, so
there is too little light to support benthic algae or rooted plants.
Many organisms living in estuaries
experience freshwater and saltwater conditions
each day with the rising and falling of tides. Based on what you learned in Concept 44.1 (pp. 953-958), explain how these changing conditions challenge the survival of these organisms.
As explained in Concept 44.1, aquatic organisms either gain or lose water by osmosis if the osmolarity of their environment differs from their internal osmolarity. Water gain
can cause cells to swell, and water loss can cause them to shrink. To avoid excessive changes in cell volume, organisms that live in estuaries must be able to compensate
for both water gain (under freshwater conditions) and water loss (under saltwater conditions).
Water leaving a reservoir behind a dam is often taken from deep layers of the reservoir. Would
you expect fish found in a river below a dam in summer to be species that prefer colder or warmer water than fish found in an undammed river? Explain.
In a river below a dam, the fish are more likely to be species
that prefer colder water. In summer, the deep layers of a reservoir are colder than the surface layers, so a river below a dam will be colder than an undammed river.
Give examples of human actions that could expand a species' distribution by changing its (a) dispersal or (b) biotic interactions.
a) Humans might transplant a species to a new area that it could not previously reach because of a geographic barrier. (b) Humans might eliminate a predator or herbivore species, such as sea urchins, from an area.
You suspect that deer are restricting the
distribution of a tree species by preferentially eating
the seedlings of the tree. How might you test this
2. One test would be to build a fence around a plot of land in an area that has trees of that species, excluding all deer from
the plot. You could then compare the abundance of tree seedlings inside and outside the fenced plot over time.
As you saw in Figure 25.20 (p. 525), Hawaiian silverswords underwent a remarkable
adaptive radiation after their ancestor reached
Hawaii, while the islands were still young. Would
you expect the cattle egret to undergo a similar
adaptive radiation in the Americas (see Figure 52.19)? Explain.
Because the ancestor of the silverswords reached isolated
Hawaii early in the islands' existence, it likely faced little competition and was able to occupy many unfilled niches. The cattle egret, in contrast, arrived in the Americas
only recently and has to compete with a well-established group of species. Thus, ts opportunities for adaptive radiation have probably been much more limited.
Suppose global air circulation suddenly reversed, with most air ascending at 30° north and south latitude and descending at the equator. At what latitude would you most likely find deserts in
Because dry air would descend at the equator instead of at 30° north and south latitude (where deserts exist today), deserts would be more likely to exist along the equator (see Figure 52.3).
Some arctic tundra ecosystems receive as little rainfall as deserts but have much more dense vegetation. Based on Figure 52.10, what climatic factor might explain this difference? Explain.
Because tundra is much cooler than deserts (see Figure 52.10), less water evaporates during the growing season and
the tundra stays more moist.
In which aquatic biomes might you find an aphotic zone?
An aphotic zone is most likely to be found in the deep waters of a lake, the oceanic pelagic zone, or the marine benthic
If you were an ecologist studying the chemical and physical limits to the distributions of species, how might you rearrange the flowchart preceding this question?
You could arrange a flowchart that begins with abiotic limitations— first determining the physical and chemical conditions under which a species could survive—and then moves through the other factors listed in the flowchart
Which of the following areas of study focuses on the exchange of energy, organisms, and materials between ecosystems?
a. population ecology
b. organismal ecology
c. landscape ecology
d. ecosystem ecology
e. community ecology
Which lake zone would be absent in a very shallow lake?
a. benthic zone
b. aphotic zone
c. pelagic zone
d. littoral zone
e. limnetic zone
Which of the following is true with respect to oligotrophic lakes and eutrophic lakes?
a. Oligotrophic lakes are more subject to oxygen depletion.
b. Rates of photosynthesis are lower in eutrophic lakes.
c. Eutrophic lake water contains lower concentrations of
d. Eutrophic lakes are richer in nutrients.
e. Sediments in oligotrophic lakes contain larger amounts of
decomposable organic matter.
Which of the following biomes is correctly paired with the description of its climate?
a. savanna—low temperature, precipitation uniform during
b. tundra—long summers, mild winters
c. temperate broadleaf forest—relatively short growing season,
d. temperate grasslands—relatively warm winters, most rainfall
e. tropical forests—nearly constant day length and temperature
Which of the following is characteristic of most terrestrial biomes?
a. annual average rainfall in excess of 250 cm
b. a distribution predicted almost entirely by rock and soil
c. clear boundaries between adjacent biomes
d. vegetation demonstrating vertical layering
e. cold winter months
The oceans affect the biosphere in all of the following ways
a. producing a substantial amount of the biosphere's oxygen.
b. removing carbon dioxide from the atmosphere.
c. moderating the climate of terrestrial biomes.
d. regulating the pH of freshwater biomes and terrestrial
e. being the source of most of Earth's rainfall.
Which statement about dispersal is false?
a. Dispersal is a common component of the life cycles of
plants and animals.
b. Colonization of devastated areas after floods or volcanic
eruptions depends on dispersal.
c. Dispersal occurs only on an evolutionary time scale.
d. Seeds are important dispersal stages in the life cycles of
most flowering plants.
e. The ability to disperse can expand the geographic distribution
of a species.
When climbing a mountain, we can observe transitions in biological communities that are analogous to the changes
a. in biomes at different latitudes.
b. at different depths in the ocean.
c. in a community through different seasons.
d. in an ecosystem as it evolves over time.
e. across the United States from east to west.
Suppose that the number of bird species is determined mainly by the number of vertical strata found in the environment. If so, in which of the following biomes would you find the
greatest number of bird species?
a. tropical rain forest
d. temperate broadleaf forest
e. temperate grassland
If the direction of Earth's rotation reversed, the
most predictable effect would be
a. no more night and day.
b. a big change in the length of the year.
c. winds blowing from west to east along the equator.
d. a loss of seasonal variation at high latitudes.
e. the elimination of ocean currents.
A group of individuals of the same species that live in the same area and interbreed, producing fertile offspring.
migration from a place (especially migration from your native country in order to settle in another)
A behavior in which an animal defends a bounded physical space against encroachment by other individuals, usually of
its own species
a group people having approximately the same age from birth until all of the individuals are dead.
A plot of the number of members of a cohort that are still alive at each age; one way to represent age-specific mortality.
exponential population growth
Growth of a population in an ideal, unlimited environment, represented by a J-shaped curve when population size is plotted over time.
logistic population growth
A model describing population growth that levels off as population size approaches carrying capacity
Reproduction in which an organism produces all of its offspring in a single event; also known as big-bang reproduction.
Selection for life history traits that are sensitive to population density; also called density-dependent selection.
Selection for life history traits that maximize reproductive success in uncrowded environments; also called density-independent selection.
Referring to any characteristic that varies with population density. Predation, competition for resources, toxic wastes, intrinsic factors, disease, territoriality.
The study of how complex interactions between biotic and abiotic factors influence variations in population size.
A collection of populations that have regular or intermittent gene flow between geographically separate units
change in a population from high birth and death rates to low birth and death rates