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The tendency of an atom to pull electrons toward itself is referred to as its _____.
which bonds are the weakest?
hydrogen bonds are weaker than covalent bonds because they involve the sharing of electrons and they are weaker than ionic bonds because they involve the attraction of partial (not full) opposite charges
In a neutral solution the concentration of _____.
hydrogen ions is equal to the concentration of hydroxide ions
what affects the pH of a solution?
The more hydroxide ions present, the more basic a solution is. The more hydrogen ions present the more acidic a solution is.
the chemical behavior of an atom depends mostly on these electrons which lie in the outermost shell
the attraction of a particular atom for the electrons of a covalent bond; the more electronegative an atom is, the more strongly it pulls shared electrons towards itself
non polar covalent bond
when an electrons are shared equally because the two atoms have the same electronegativity-this tug-of-war creates a standoff
polar covalent bond
when the electrons of the bond are not shared equally so that one atom is relatively more negative than the other
formed between two atoms when one atom completely pulls an electron from the second atom and the two atoms are held together because one is now negatively charged (containing an extra electron) and the other is positively charge (because it has lost an electron)
what properties of water stabilize the temperature and lead to evaporative cooling?
As a result of hydrogen bonding among water molecules, it takes a relatively large heat loss or gain for each 1 degree C change in temperature.
The surface molecules with the highest kinetic energy are most likely to escape into gaseous form; the average kinetic energy of the remaining surface molecules is thus lower.
why does ice float?
ice is less dense than liquid water. as water freezes a crystal lattice is formed by hydrogen bonds joining all water molecules in the liquid. these hydrogen bonds keep the different water molecules at "arms length" from one another.
why is the idea of ice floating important for aquatic organisms living in temperate environments?
since ice floats, water freezes from the top down. organisms under ice are insulated from the freezing conditions above the water providing relatively warm and safe conditions.
the number of grams of a substrate that equals its molecular weight in Daltons and contains Avogadro's number of number molecules
how do you determine the molecular weight or mole weight of compound?
the molecular weight of the a molecule is equal to the sum of the atomic masses of the atoms making up the molecule
About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements make up approximately 96% of living matter?
carbon, hydrogen, nitrogen, oxygen
The type of bonding and the numbers of covalent bonds an atom can form with other atoms is determined by _____.
the number of unpaired electrons in the valence shell
The atomic number of each atom is given to the left of each of the elements below. Which of the atoms has the same valence as carbon (12
Hydrogen bonding is most often seen _____.
when hydrogen is covalently bonded to an electronegative atom
Which of the following correctly describes chemical equilibrium?
Forward and reverse reactions continue with no effect on the concentrations of the reactants and products.
Two atoms appear to have the same mass number. These atoms
must have the same number of protons + neutrons.
If an atom of sulfur (atomic number 16) were allowed to react with atoms of hydrogen (atomic number 1), which of the molecules below would be formed?
What is the maximum number of hydrogen atoms that can be covalently bonded in a molecule containing two carbon atoms?
Geometric isomers are molecules that _____.
differ in the arrangement of their atoms about a double bond
which of the functional groups behaves as a base?
the electronegativity of nitrogen means that amino groups tend to pick up hydrogen atoms
Which of the functional groups is characteristic of thiols?
Thiols are characterized by the presence of a sulfhydryl group.
Which of the functional groups plays a major role in energy transfer?
Phosphate groups are a component of ATP.
Which of the functional groups is characteristic of a ketone?
A carbonyl group in the middle of a carbon skeleton characterizes ketones.
Which of functional groups behaves as an acid?
By donating hydrogen ions, carboxyl groups act as an acid.
Which action could produce a carbonyl group?
the replacement of the -OH of a carboxyl group with hydrogen
Which of the functional groups is most likely to gain a proton and become positively charged?
An amino group acts as a base and can pick up protons from the surrounding medium, becoming positively charged.
Which of the following statements about the formation of polypeptides from amino acids is true?
A bond forms between the carboxyl functional group of one amino acid and the amino functional group of the other amino acid.
A function of cholesterol that does not harm health is its role _____.
as a component of animal cell membranes
Which of the following statements about nucleotide structure is false?
The phosphate group is bonded to the nitrogenous base. (it is bonded to the sugar in actuality)
Which of the following statements about DNA structure is true?
The nucleic acid strands in a DNA molecule are oriented antiparallel to each other.
Some regions of a polypeptide may coil or fold back on themselves. This is called _____, and the coils or folds are held in place by _____.
secondary structure ... hydrogen bonds
Which of the following statements concerning unsaturated fats is true?
They have double bonds in the carbon chains of their fatty acids.
In eukaryotic cells the first step in protein synthesis is the _____.
transferring of information from DNA to messenger RNA
Which of these manufactures cellular membranes by adding membrane proteins and phospholipids to its own membrane?
rough endoplasmic reticulum
The _____ is a selective barrier, regulating the passage of material into and out of the cell.
which structure provides the cell with structural support?
microfilaments (they are components of the cytoskeleton)
Which of the following are common traits of chloroplasts and mitochondria?
both have their own DNA and ribosomes
_____ aid in the coordination of the activities of adjacent animal cells.
gap junctions (gap junctions allow for the passage of material between cells, thus facilitating communication between these cells.)
A biologist wants specifically to examine the surfaces of different types of cells in kidney tubules of small mammals. The cells in question can be distinguished by external shape, size, and 3-D characteristics. Which of the following would be the optimum method for her study?
scanning electron microscopy
Which statement correctly describes the nuclear envelope of a eukaryotic cell?
the nuclear envelope is continuous with the endoplasmic reticulum
A cell has the following molecules and structures: enzymes, DNA, ribosomes, plasma membrane, and mitochondria. It could be a cell from
nearly any eukaryotic oragism
Which of the following contain the 9 + 2 arrangement of microtubules, consisting of nine doublets of microtubules surrounding a pair of single microtubules?
both flagella and motile cilia
The smallest cell structure that would most likely be visible with a standard (not super-resolution) research-grade light microscope is
Vinblastine, a drug that inhibits microtubule polymerization, is used to treat some forms of cancer. Cancer cells given vinblastine would be unable to
separate chromosomes during cell division.
The diameter of a typical eukaryotic cell is approximately ten times the diameter of a typical prokaryote. What is the ratio of the volume of typical eukaryotic:prokaryotic cells?
What do the cell walls of plants and the extracellular matrix of animal cells have in common?
They have functional connections with the cytoskeleton inside the cell.
Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through
what does it mean when a cell is in a hypertonic solution?
There is a greater concentration of solute outside the cell.
how do you know when a cell has been placed into a hypotonic solution?
it will swell (it will gain water when placed into a hypotonic solution)
how do you know when a cell has been placed into a hypertonic solution?
the cell will shrink (it will lose water when placed in the hypertonic solution)
Based on Figure 7.21 in your textbook, which of these experimental treatments would increase the rate of sucrose transport into the cell?
decreasing extracellular pH
Which factors affect the rate of osmotic movement of water?
The rate of osmosis increases with increasing differences in solute concentrations between two solutions separated by a selectively permeable membrane.
What happens when two solutions separated by a selectively permeable membrane reach osmotic equilibrium?
Water molecules move between the two solutions, but there is no net movement of water across the membrane.
What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule?
The reaction A --> B + C + heat is released in a(n) _____ reaction.
exergonic (energy is being released)
A(n) _____ reaction occurs spontaneously.
exergonic (the products have less potential energy than the reactants in these types of reactions)
What is the fate of the phosphate group that is removed when ATP is converted to ADP?
It is acquired by a reactant in an endergonic reaction.
What is energy coupling?
the use of energy released from an exergonic reaction to drive an endergonic reaction
In glycolysis, ATP molecules are produced by _____.
substrate-level phosphorylation (A phosphate group is transferred from glyceraldehyde phosphate to ADP.)
Which of the following describes the process of glycolysis?
It represents the first stage in the chemical oxidation of glucose by a cell.
A molecule that is phosphorylated
has an increased chemical potential energy; it is primed to do cellular work.
Which kind of metabolic poison would most directly interfere with glycolysis?
an agent that closely mimics the structure of glucose but is not metabolized
Which statement about the citric acid cycle is correct?
The last reaction in the citric acid cycle produces a product that is a substrate for the first reaction of the citric acid cycle.
True or false? The potential energy in an ATP molecule is derived mainly from its three phosphate groups.
Which process is not part of the cellular respiration pathway that produces large amounts of ATP in a cell?
Into which molecule are all the carbon atoms in glucose ultimately incorporated during cellular respiration?
Which of the following statements about the electron transport chain is true?
NADH and FADH2 donate their electrons to the chain.
True or false? The reactions that generate the largest amounts of ATP during cellular respiration take place in the mitochondria.
During electron transport, energy from _____ is used to pump hydrogen ions into the _____.
NADH and FADH2 ... intermembrane space
The proximate (immediate) source of energy for oxidative phosphorylation is _____.
kinetic energy that is released as hydrogen ions diffuse down their concentration gradient
A figure expressing the acidity or alkalinity of a solution on a logarithmic scale on which 7 is neutral, lower values are more acidic and higher values are more basic
what would be the expected concentrations of hydrogen ions and of hydroxyl ions in pure water?
there is only one ten-millionth of a mole of hydrogen ions per liter of pure water and an equal number of hydroxide ions
how are important biological macromolecules lengthened and shortened by condensation and hydrolysis reactions?
every time a unit is added to a macromolecule a molecule of water is formed by removing a water molecule in what is known as a condensation reaction. Macromolecules are broken down by hydrolysis of macromolecules. In this breakdown, a hydrogen atom is added to one of the molecules and OH is added to the other
what is a triglyceride molecule and what is its general structure?
they are fats or oils and they are made up of three fatty acid molecules covalently bonded to glycerol molecule.
what is the difference between a saturated and unsaturated bond in fatty acids?
in a fatty acid a saturated bond is a single covalent bond between two carbon atoms while an unsaturated bond is a double covalent bond between two carbon atoms
what is the difference between a fat and an oil?
fats are solid at room temperature while oils are liquid.
why are natural oils good for you?
oils with natural unsaturated bonds are associated with reduced risk of atherosclerosis
what is the basic structure of an amino acid?
an amino acid contains an asymmetric carbon which is attached to a hydrogen atom, a carboxyl group, an amino group, and a side chain of variable structure
what are the three structural groupings of amino acids and how many amino acids are there in each group?
the three groups and number of amino acids in each are: nonpolar - 9 amino acids, polar - 6 amino acids, and charged - 5 amino acids
what is the backbone of the polypeptide and how is it formed?
the primary structure of a polypeptide is determined by the sequence of amino acids which are bonded together by covalent bonds between the amino group on one amino acid with the carboxyl group on the next amino acid. The "backbone" is made up of the sequence of the amino group, asymmetric carbon, and carboxyl group in each amino acid and does not include the side chains of amino acids.
what do nucleic acids do in cells?
the two types, DNA and RNA, enable living organisms to reproduce their complex components from one generation to another
what are the 3 basic components of a nucleotide?
a nitrogenous base, a five-carbon sugar, a phosphate group
what is the structural difference between a purine and pyrimidine?
purines are larger than pyrimidines with an addition 5 membered ring fused to the original six membered ring
how do the movements of cilia and flagella differ?
cilia move back and forth like oars while flagella undulate in a snake like motion
what is meant by the "9+2" structure of cilia and flagella in eukaryotic cells?
all cilia and flagella from eukaryotic cells are made up a ring of 9 pairs of microtubules arranged in a circle surrounding another pair microtubules
hollow tubes made up tubulin molecules
maintains cell shape, moves the cell, moves chromosome in cell division, moves organelles
two intertwined strands of actin, each a polymer of actin subunits
muscle contraction, cytoplasmic streaming, cell motility, cell division
fibrous proteins supercoiled into thicker cables
anchors nucleus and certain other organelles, forms nuclear lamina
the tendency of a fluid, usually water, to pass through a semipermeable membrane into a solution where the solvent concentration is higher, thus equalizing the concentrations of materials on either side of the membrane.
when polar molecules and ions impeded by lipid bilayer of membrane diffuse passively with the help of the transport proteins that span the membrane
two models that explain how facilitated diffusion occurs
channel proteins (simply provide corridors and allow specific molecules or ions to cross the membrane) and carrier proteins (undergo a subtle change in shape that somehow translocates the solute-binding site across the membrane)
transport of solutes across a membrane against a concentration gradient with the help of energy and transport proteins. an ATPase is an enzyme that hydrolyzes ATP to release energy. this energy is used to drive active transport
what is an electrogenic pump?
the electrogenic pump provides an example of an active transport in that it moves ions against their concentration gradient using energy released from the hydrolysis of ATP
a single ATP-powered pup that transports a specific solute can indirectly drive the active transport of several other solutes in a this mechanism
a compound binds with an enzyme at a location other than the active site on the enzyme. binding of the compound changes the structure of the enzyme (quaternary protein structure)
how can the rate of reaction be increased or decreased by allosteric regulation?
if the compound locks the enzyme in its active form, the compound is classified as a positive regulator; this maximizes the rate of the reaction. if the compound locks the enzyme into its inactive form, the compound is classified as a negative regulator; this minimizes the rate of reaction
a metabolic pathway is switched off by the inhibitory binding of its end product to an enzyme that acts early in the pathway
how does feedback inhibition regulate the metabolic pathway that produces isoleucine in plant and bacterial cells?
as isoleucine accumulates, it slows down its own synthesis by allosterically inhibiting the enzyme for the first step of the pathway. feedback inhibition thereby prevents the cell from wasting chemical resources by making more isoleucine than necessary
examples of molecules that make up the Electron Transport System
flavoprotein, iron-sulfur proteins, ubiquinone, cytochromes
in an active mitochondrion, would the intermembrane space or the matrix have a lower pH?
the intermembrane space would have a lower pH because electron transport moves protons from the matrix to the intermembrane space across the inner mitochondrial membrane
a mechanism by which energy stored in proton (hydrogen ion) gradient is used to make ATP
what are the key compounds in glycolysis and the citric acid cycle that are related to catabolism of fats and proteins?
key molecules for fats are glyceraldehyde 3P and acetyl CoA.
In cellular respiration, a series of molecules forming an electron transport chain alternately accepts and then donates electrons. What is the advantage of such an electron transport chain?
The advantage of an electron transport chain is that a small amount of energy is released with the transfer of an electron between each pair of intermediates.
How will a healthy individual's ATP production change during an eight-hour fast?
Catabolism can harvest energy from fats in fatty tissue or from storage proteins or glycogen in the liver. As a result, glycolysis and cellular respiration continue to produce ATP during a fast.
Energized electrons from ____ enter an electron transport chain and are then used to reduce NADP+.
True or false? The chemiosmotic hypothesis states that the synthesis of ATP generates a proton gradient that leads to electron flow through an electron transport chain.
false (The chemiosmotic hypothesis states that the flow of electrons through an electron transport chain generates a proton gradient that leads to the synthesis of ATP.)
According to the chemiosmotic hypothesis, what provides the energy that directly drives ATP synthesis?
True or false? The region of ATP synthase that catalyzes the production of ATP from ADP and inorganic phosphate spans the chloroplast membrane.
false (The region of ATP synthase that catalyzes ATP production protrudes out of, but does not span, the chloroplast membrane; the region that spans the membrane is an ion channel through which protons can pass.)
Chloroplast membrane vesicles are equilibrated in a simple solution of pH 5. The solution is then adjusted to pH 8. Which of the following conclusions can be drawn from these experimental conditions?
ATP will not be produced because there is no ADP and inorganic phosphate in the solution. (This statement is true; although the proton gradient is present, ADP and inorganic phosphate are required to make ATP and were not added to the reaction.)
Plants are photoautotrophs. What does this mean?
They use light energy to drive the synthesis of organic molecules from inorganic materials.
A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain?
Why is it difficult to observe individual chromosomes with a light microscope during interphase?
they have uncoiled to form long thin strands (except during the M phase)
During anaphase centromeres come apart, and sister chromatids become full-fledged chromosomes, which migrate to opposite poles of the cell.
During prophase a homologous pair of chromosomes consists of _____.
two chromosomes and four chromatids
Which of the following is a function of the S phase in the cell cycle?
The synthesis of sister chromatids
For the first several divisions of early frog embryos, cells proceed directly from the M phase to the S phase and back to M without gaps. Which of the following is likely to be true about dividing cells in early frog embryos?
The cells get smaller with each generation.
(without gap phases the cells have no opportunity to grow)
True or false? The M phase is characterized by the replication and division of a cell's chromosomes.
false (Correct: Cells replicate their chromosomes during the S phase and divide partition their chromosomes during the M phase.)
If an organism normally has 34 chromosomes, how many molecules of DNA should there be in the G1 phase of the cell cycle?
A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing _____ chromosomes.
What number and types of chromosomes are found in a human somatic cell?
44 autosomes and 2 sex chromosomes
What is the best evidence telling you whether this cell is diploid or haploid?
The cell is diploid because it contains two sets of chromosomes.
In his breeding experiments, Mendel first crossed true-breeding plants to produce a second generation, which were then allowed to self-pollinate to generate the offspring. How do we name these three generations?
Each chromosome in this homologous pair possesses a different allele for flower color. Which statement about this homologous pair of chromosomes is correct?
These homologous chromosomes represent a maternal and a paternal chromosome.
When a dominant allele coexists with a recessive allele in a heterozygote individual, how do they interact with each other?
they do not interact at all
What is the difference between heterozygous and homozygous individuals?
All of the gametes from a homozygote carry the same version of the gene while those of a heterozygote will differ.
When constructing a Punnett square, the symbols on the outside of the boxes represent _______, while those inside the boxes represent _______.
True or false? In diploid organisms, a dominant phenotype will only be expressed if the individual is homozygous dominant for that trait.
If an organism with the genotype AaBb produces gametes, what proportion of the gametes would be Bb?
None (Alleles of the same gene must separate during gamete formation; thus, the two B alleles would be distributed to different gametes.)
Two mice are heterozygous for albinism (Aa) . The dominant allele (A) codes for normal pigmentation, and the recessive allele (a) codes for no pigmentation. What percentage of their offspring would have an albino phenotype?
25 (The offspring would be in a 3:1 ratio of normally pigmented mice to albino mice.)
A tall, purple-flowered pea plant (TtPp) is allowed to self-pollinate. (The recessive alleles code for short plants and white flowers.) The phenotypic ratio of the resulting offspring is 9:3:3:1. What is the genotype of the plant whose phenotype appeared once out of every 16 offspring (the "1" in the 9:3:3:1 ratio)?
ttpp (The smallest phenotypic group consists of the homozygous recessive plants, which in this case are short and white flowered.)
The fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment most probably indicates which of the following?
All of the genes controlling the traits behaved as if they were on different chromosomes.
Black eyes are dominant to orange eyes, and green skin is dominant to white skin. Sam, a MendAlien with black eyes and green skin, has a parent with orange eyes and white skin. Carole is a MendAlien with orange eyes and white skin. If Sam and Carole were to mate, the predicted phenotypic ratio of their offspring would be _____.
1 black eyes, green skin : 1 black eyes, white skin : 1 orange eyes, green skin : 1 orange eyes, white skin
In order to determine the genotype of a MendAlien with black eyes and green skin, you would cross this individual with a(n) _____ individual.
A cross between an individual with orange eyes and green skin and an individual with black eyes and white skin is an example of a _____ cross.
A phenotypic ratio of 9:3:3:1 in the offspring of a cross indicates that _____.
both parents are heterozygous for both genes
An individual heterozygous for eye color, skin color, and number of eyes mates with an individual who is homozygous recessive for all three characters; what would be the expected phenotypic ratio of their offspring? [Hint: B = black eyes, b = orange eyes; G = green skin, g = white skin; C = two eyes, c = one eye]
1 black eyes, green skin, two eyes : 1 black eyes, green skin, one eye : 1 black eyes, white skin, two eyes : 1 black eyes, white skin, one eye : 1 orange eyes, green skin, two eyes : 1 orange eyes, green skin, one eye : 1 orange eyes, white skin, two eyes : 1 orange eyes, white skin, one eye
A BbGg x bbgg cross yields a phenotypic ratio of approximately 5 black eyes, green skin : 5 orange eyes, white skin : 1 black eyes, white skin : 1 orange eyes, green skin. Which of the following best explains these results?
Mendel's law of independent assortment is being violated.
In a situation in which genes assort independently, what is the ratio of the gametes produced by an AaBB individual?
1 AB : 1 aB
Look at the Punnett square, which shows the predicted offspring of the F2 generation from a cross between a plant with yellow-round seeds (YYRR) and a plant with green-wrinkled seeds (yyrr). Select the correct statement about wrinkled yellow seeds in the F2 generation.
The chance that an individual taken at random from the F2 generation produces wrinkled seeds is 25% and the chance that the same individual produces yellow seeds is 75%. (Read about the Law of Independent Assortment in Concept 14.1 and about how to solve complex genetics problems using the rules of probability in Concept 14.2.)
How do cells acquire homologous chromosome pairs that carry the alleles that are independently assorted?
fusion of gametes (During fertilization, gametes bring together homologous chromosomes to generate a diploid individual.)
Which of the following statements most accurately describes the process of independent assortment?
Alleles of different genes segregate from one another in a random manner.
True or false? The principle of independent assortment is best illustrated by events that take place during metaphase II, during which sister chromatids segregate independently of each other.
false (The principle of independent assortment is best illustrated by events that take place during metaphase I, during which nonhomologous chromosomes segregate independently of each other.)
How many genetically unique types of gametes could be produced by an individual with the genotype RrYY?
2 (The gametes would be either RY or rY.)
Which of the following parental genotypes would yield a 1:1:1:1 phenotypic ratio in the offspring?
Which of the following is true about a plant with the genotype AABbcc?
It is homozygous at two loci.
How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?
Consider pea plants with the genotypes GgTt and ggtt . These plants can each produce how many type(s) of gametes?
four.....one (GgTt individuals can produce the following gametes: GT, Gt, gT, and gt. A ggtt plant can produce only gt.)
You cross a true-breeding red-flowered snapdragon with a true-breeding white-flowered one. All of the F1 are pink. What does this say about the parental traits?
Red shows incomplete dominance over white.
Which of the following describes the ability of a single gene to have multiple phenotypic effects?
In humans, what determines the sex of offspring and why?
The male gamete determines sex because each male gamete can contribute either an X or a Y chromosome. (In humans, the male produces both X- and Y-bearing sperm, whereas females only produce X-bearing eggs.)
In general, the frequency with which crossing over occurs between two linked genes depends on what?
how far apart they are on the chromosome (The farther apart two genes are, the greater the probability that a crossover will occur between them, and therefore the greater the recombination frequency.)
What is a nondisjunction?
An error in cell division that causes homologous chromosomes or sister chromatids to move to the same side of the dividing cell
When can nondisjunction occur? Choose the best answer.
Nondisjunction errors can occur in meiosis I, when homologous chromosomes fail to separate, or in either mitosis or meiosis II, when sister chromatids fail to separate
What kind of cell results when a diploid and a haploid gamete fuse during fertilization?
a triploid cell
Of the following chromosomal abnormalities, which type is most likely to be viable in humans?
If a diploid cell undergoes meiosis and produces two gametes that are normal, and one with n − 1 chromosomes, and one with n + 1 chromosomes, what type of error occurred?
A nondisjunction error occurred in meiosis II, in which both sister chromatids of a chromosome migrated to the same pole of the cell.
If a diploid cell undergoes meiosis and produces two gametes with n + 1 chromosomes and two gametes with n− 1 chromosomes, what type of error occurred?
A nondisjunction error occurred in meiosis I, in which both members of a homologous pair migrated to the same pole of the cell.
Which of these descriptions of the behavior of chromosomes during meiosis explains Mendel's law of segregation?
The two alleles for each gene separate as homologous chromosomes move apart during anaphase I.
Imagine a human disorder that is inherited as a dominant, X-linked trait. How would the frequency of this disorder vary between males and females?
Females would display this disorder with greater frequency than males. (Men have only one X chromosome, whereas women have two. Thus, women have twice the chance of inheriting the dominant allele that causes this disorder. Remember that the disorder is caused by a dominant allele, so an individual who inherits a single dominant allele will display the disorder. Read about the inheritance of X-linked genes.)
Which of these is a difference between a DNA and an RNA molecule?
DNA is double-stranded, whereas RNA is single-stranded.
In a nucleotide, the nitrogenous base is attached to the sugar's _____ carbon and the phosphate group is attached to the sugar's _____ carbon.
1' ... 5'
In a DNA double helix an adenine of one strand always pairs with a(n) _____ of the complementary strand, and a guanine of one strand always pairs with a(n) _____ of the complementary strand.
thymine ... cytosine
What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?
DNA polymerase can join new nucleotides only to the 3' end of a growing strand.
A biochemist isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. When she adds some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?
DNA is a self-replicating molecule. What accounts for this important property of DNA?
The nitrogenous bases of the double helix are paired in specific combinations: A with T and G with C.
What name is given to the process in which a strand of DNA is used as a template for the manufacture of a strand of pre-mRNA?
What name is given to the process in which the information encoded in a strand of mRNA is used to construct a protein?
What is the process called that converts the genetic information stored in DNA to an RNA copy?
Transcription begins at a promoter. What is a promoter?
A site in DNA that recruits the RNA Polymerase
Which of the following statements best describes the promoter of a protein-coding gene?
The promoter is a nontranscribed region of a gene.
What determines which base is to be added to an RNA strand during transcription?
Base pairing between the DNA template strand and the RNA nucleotides
Which of the following terms best describes the relationship between the newly synthesized RNA molecule and the DNA template strand?
What happens to RNA polymerase II after it has completed transcription of a gene?
It is free to bind to another promoter and begin transcription.
During RNA processing a(n) _____ is added to the 3' end of the RNA.
a long string of adenine nucleotides
For any given gene, what ultimately determines which DNA strand serves as the template strand?
the base sequence of the gene's promoter
After an RNA molecule is transcribed from a eukaryotic gene, what are removed and what are spliced together to produce an mRNA molecule with a continuous coding sequence?
Alternative RNA splicing _______.
can allow the production of proteins of different sizes and functions from a single mRNA.
what mutation would be most dangerous to a cell?
deletion of one nucleotide (it would shift the reading frame, altering the coding for all subsequent amino acids. In most cases, this would destroy the function of the protein produced from this gene. Read about the genetic code and point mutations.)
Which of these is NOT a component of the lac operon?
regulatory gene (while not a part of the operon, plays a role in regulating the expression of the genes of the operon.)
what happens when The lysogenic cycle is making a transition to the lytic cycle?
Phage DNA has exited the bacterial chromosome as a prelude to taking over the host's metabolic machinery.
The unpaired nucleotides produced by the action of restriction enzymes are referred to as _____.
In order to insert a human gene into a plasmid, both must _____
be cut by the same restriction enzyme (Doing so will result in the formation of complementary sticky ends.)
What enzyme forms covalent bonds between restriction fragments?
DNA ligase (DNA ligase catalyzes the formation of covalent bonds between restriction fragments.)
what is the process by which a bacterium takes up a plasmid from the surrounding solution?
What information can not be obtained from the sequence of a gene?
Whether the gene is methylated. (Although the gene's sequence may reveal the presence of methylation targets like cytosine (C), it does not give information about whether such bases have been methylated.)
What is the polymerase chain reaction (PCR)?
PCR is an in vitro DNA synthesis reaction that produces many copies of a single DNA fragment.
True or false? Comparison of the sequences of the same gene across species can give some insight into the existence of a common ancestor with that gene.
True or false? The Taq enzyme is a type of DNA polymerase that allows researchers to separate the DNA strands during the annealing step of the PCR cycle without destroying the polymerase.
False (Taq polymerase is derived from a species of bacteria living in hot springs, which makes it stable at the high temperature required for the denaturation step of PCR.)
How many DNA molecules would there be after four rounds of PCR if the initial reaction mixture contained two molecules?
32 (Thirty-two DNA molecules are produced if two molecules are doubled four times.)
During which step in the PCR cycle are nucleotides used?
extension (Nucleotides are used to synthesize the complementary strand to the DNA template during the extension step.)
During which step in the PCR cycle do primers form bonds with a single-stranded template?
annealing (Primers form hydrogen bonds with the single-stranded DNA template during the annealing step.)
True or false? The use of growth hormone isolated from cadavers was banned mainly because there were not enough cadavers to supply the hormone.
False (The use of growth hormone isolated from cadavers was banned mainly because the isolated hormone was potentially contaminated with prion proteins.)
Which of the following statements best describes the function of reverse transcriptase?
The function of reverse transcriptase is similar to the reverse of transcription; it makes a single strand of complementary DNA (cDNA) from mRNA.
Which of the following steps would be performed last when screening a cDNA library?
Match the region of radioactivity on the filter with the corresponding plate.
How can large quantities of protein be produced from a bacterial colony containing the gene of interest?
Once a cDNA is put into a plasmid with a bacterial promoter, the bacteria will transcribe and translate the gene.
True or false? The term "sticky ends" refers to the overhanging ends on DNA that are generated by restriction enzymes, which can base pair with any DNA molecules that contain complementary sticky ends.
What was the main goal of the Human Genome Project (HGP)?
to map all the human genes and determine the nucleotide sequence of the entire human genome
what is a G-protein-linked-receptor?
This kind of receptor spans the cell membrane, and as you might guess, it works through a protein called a G protein.
what happens when the signal protein binds to the G-protein-linked-receptor?
When the signal molecule binds to the receptor, the receptor becomes activated. It is now able to activate a specific G protein by causing GTP to displace GDP on the G protein. The activated G protein then binds to another protein, usually an enzyme, and alters its activity. Then the G protein hydrolyzes its GTP and reverts to its inactive form— ready to respond to another signal.
receptor tyrosine kinase
Binding of signal molecules causes two polypeptides to join, activating parts of each that act as tyrosine-kinase enzymes, which then phosphorylate tyrosines in the tail of the other polypeptide.
The receptor protein is now recognized by specific relay proteins inside the cell. One receptor tyrosine kinase may activate several relay proteins at once, triggering several different effects within the cell.
ion channel receptor
Some membrane receptors are ligand-gated ion channels. They are protein pores in the plasma membrane that allow or block the passage of certain ions through the membrane. For example, this occurs when one neuron signals another via a neurotransmitter.
what happens when the signal molecule binds to the ion channel receptor?
The signal molecule attaches to a site on the ion channel protein. This changes the shape of the protein, opening a channel through the membrane. Ions flow through the channel, and the change in ion concentration triggers a cellular response.
Which of these extracellular signal molecules could diffuse through a plasma membrane and bind to an intracellular receptor?
estrogen (Nonpolar molecules can diffuse through the plasma membrane and bind to intracellular receptors.)
A(n) _____ is an example of a signal molecule that can bind to an intracellular receptor and thereby cause a gene to be turned on or off.
What role does a transcription factor play in a signal transduction pathway?
By binding to DNA it triggers the transcription of a specific gene.
what, when activated by a signal transduction pathway, moved from the cytoplasm to the nucleus of a cell?
_____ catalyzes the production of _____, which then opens an ion channel that releases _____ into the cell's cytoplasm.
Phospholipase C ... IP3 .... Ca2+
A protein kinase activating many other protein kinases is an example of _____.
amplification (By activating many other molecules the initial signal is amplified.)
The cleavage of glycogen by glycogen phosphorylase releases _____.
glucose-1-phosphate (Glycogen is a polysaccharide composed of glucose monomers.)
A toxin that inhibits the production of GTP would interfere with the function of a signal transduction pathway that is initiated by the binding of a signal molecule to _____ receptors.
Which molecules determine the tissue specificity of hormones?
receptors (Hormones bind to receptors on target cells and trigger a cellular response.)
True or false? Lipid-insoluble hormones affect their target cells by binding to receptors inside the cell.
false (Lipid-insoluble hormones cannot cross the plasma membrane and get into the cell, so they must bind to receptors on the cell surface and transduce their signals through signal transduction pathways.)
Which of the following statements about lipid-soluble hormones is true?
Lipid-soluble hormones act by affecting the transcription of genes.
Which of the following is a structure that allows hormone-receptor complexes to bind to specific DNA sequences?
What is the role of cAMP in the signal transduction pathway activated by epinephrine?
It binds to and activates protein kinase A, which then phosphorylates other enzymes in the signal transduction pathway
True or false? For a signal transduction pathway to be activated, hormones must be present in the bloodstream at very high concentrations.
false (Only low concentrations of hormones are needed in the bloodstream to activate a signal transduction pathway, which works by producing second messengers inside the cell that amplify the hormonal signal.)
Mendel's tall versus dwarf phenotypes result from differences in stem elongation. The differences in stem elongation are due to differences in production of ___.
A plant seedling bends toward sunlight because
auxin is found in greatest abundance on the dark side of the stem.
Signal transduction pathways often involve enzymes that remove phosphates from proteins. These enzymes are __.
Epinephrine first binds with a(n) ___ type of receptor to produce an increase in glycogen phosphorylase activity
G protein coupled
what specific events during electron transport in the chloroplast produce an imbalance in H+?
the H+ gradient across the thylakoid membrane is caused 1) the splitting of water in the thylakoid space and 2) the shuttling of H+ from the stroma to the thylakoid space every time plastoquinone is reduced then oxidated
the substrate for the enzyme rubisco that leads to the carboxylation of ribulose biphosphate
under what conditions did rubisco evolve on the earth?
evolved on the early earth when the atmosphere was characterized by high concentrations of carbon dioxide and virtually no oxygen
what are "good" reactions involving rubisco and ribulose biphosphate?
when the reaction starts with 5 carbons per reaction and ends up with 6 carbons. these "good" reactions are limited by CO2
what are "bad" reactions involving rubisco and ribulose biphosphate?
when the reaction starts with 5 carbons per reaction and ends up with 5 carbons. favored under hot dry conditions because stomates close to conserve water and the CO2 decreases as it is used up by photosynthesis and the reaction rate declines
how many products are formed by mitosis?
two diploid daughter cells genetically identical to the mother
what would it mean if somatic cells are thought to be 2n=32?
this means that the cells would be diploid and contain a total of 32 chromosomes
crossing over or a physical exchange of genetic material between non-sister chromatids form homologous chromosomes
The interaction of genes that are not alleles, in particular the suppression of the effect of one such gene by another.
abnormal number of chromosomes in an individual due to nondisjunction of paired chromosomes during gamete formation (meiosis) and the formation of a zygote with the incorrect number of chromosomes
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