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Bio 161

Terms in this set (96)

both __ and __ ions can "leak" through the plasma membrane due to diffusion
sodium--- potassium
part 1 ___ is an active transport process that require ATP which involves transporting an endosome from 1 side of the cell to ther other side.
transcytosis
part 2 and then realseasing the contents enclosed in the endosome to the outside of cell by ___
excocytosis
If you placed a red blood cell in pure water what would happen to it and why?
this would mean the extracellular fluid is 100% water and no solutes are present. The inside of the cell would have solutes so this would make this a hypotonic tonicity with more water outside. The water would move into the RBC and the cell would swell and burst.
what is the plasma membrane mailnly composed of?
a bilayer (two layers, double layer) of phospholipids molecules.
what are some functions of the plasma membrane?
it acts as a site of cell to cell interaction and recognition for other molecules to attach to it; it is best described as being selectively permeable; it allows certain molecules in and keeps others out and vice- versa
waht are the fingerlike projections that greatly increase the absorbing surface of cells and whrer do you find them?
microvilli found in the small intestine
what affects the rate of diffusion?
higher the temperature the faster the rate of diffusion; the greater the concentration gradient the faster the rate of diffusion; the greater the molecular weight of a substance the faster the rate of diffusion
what influences enzyme structure?
Environment: temperature and pH; Regulation: competitive inhibition, allosteric regulation, and covalent mods.
DNA structure
5' -> 3'
deoxyribose sugar
helical
antiparallel complimentary base pairing
ACGT
RNA structure
ribose sugar
single stranded (folds up)
ACGU
If a hydrogen atom gains an electron, then __________.
it acquires an negative charge
An iceberg near the Arctic Circle represents which unusual property of water?
Its higher density as a liquid than as a solid
Liquid water has surface tension, has a high specific heat, and functions effectively as a solvent for polar covalent and ionically bonded molecules. What feature of water imparts these properties?
Water readily forms hydrogen bonds with other water molecules and with polar solutes.
Which of the following substances has the lowest concentration of protons?
The one with more basic concentration
Which of the following contains a polar covalent bond?
H-H
O-H
NaCl
C-H
O-H
Which of the following groupings of atoms determines molecular properties and the types of chemical reactions in which a molecule participates?
functional groups
An acid is defined by which of the following statements?
It donates protons to other substances in a solution.
Many different chemical reactions are occurring inside your body. What type of system is your body?
closed system
open system
isolated system
independent system
open system
When a reaction is at equilibrium, __________.
there is no net change in the concentration of reactants and products
The electrons in a water molecule are shared unequally, which results in the formation of __________.
partial charges on the oxygen and hydrogen atoms
Which of the following is necessary for an atom to participate in the formation of a double covalent bond?
The participating atoms must have two or more unpaired electrons.
What is the significance of the minerals present in hydrothermal vents in the surface metabolism model of chemical evolution?
The minerals helped catalyze the formation of organic molecules.
Which of the following best describes why ionic molecules dissolve and dissociate in water?
Water is a polar, covalently bonded substance.
Which four elements make up 96 percent of matter found in living organisms?
Hydrogen, carbon, oxygen, and nitrogen
Why is the atomic weight of most elements not a whole number?
The weight of an element is a weighted average of all the masses of naturally occurring isotopes of that element.
For a chemical reaction to proceed spontaneously, __________.
it must proceed without an input of external energy
What is the significance of buffers in biological systems?
They help maintain homeostasis with respect to pH
An organic molecule always contains one or more atoms of __________.
carbon
An element in the second row of the periodic table that has four valence electrons would most likely __________.
form what kinds of bonds
An element in the second row of the periodic table that has four valence electrons would most likely __________.
What is the difference between 12C and 13C?
13C has one more neutron than 12C.
During digestion of food, large complex biological molecules (polymers) are often broken down into their smaller simpler building blocks (monomers). This is accomplished by using _______________.
hydrolysis reactions
As an example of a(n) __________, household bleach can be characterized as having a __________.
base; pH greater than 7
Substrates are also known as __________.
reactants
Where do substrates bind to an enzyme?
active site
Aspartate and glutamate are two amino acids that are highly soluble in water. This is best explained by the fact that they __________.
have electrically charged side chains or R groups
Sickle-cell anemia results when valine replaces glutamate at position six of the β-globin subunit of hemoglobin. The sickling seen in red blood cells with the defective hemoglobin subunit results from a change in the __________.
primary structure of hemoglobin
Proteins are critical in living organisms. What is one example of the many important functions of proteins in organisms?
Proteins impart mobility to entire cells and molecules within cells.
Researchers doubt that proteins were the first living entity because __________.
proteins do not serve as a good template for replication
A chemical that breaks disulfide bonds might destroy which level of protein structure?
the tertiary structure
Which of the following statements is true regarding the amino acids that have R groups or side chains that consist solely of carbon and hydrogen atoms?
they rarely participate in chemical reactions
Many proteins fold spontaneously because __________
the bonds that form secondary and tertiary structure are energetically favorable
What bond type is responsible for the secondary structure of a protein?
hydrogen
A hydrophobic R group would most likely be found __________.
buried in the interior of a protein
Which statement best describes the R groups or side chains of amino acids?
The nature of R groups or side chains determines how soluble each amino acid is in water
The chemical structure of valine and asparagine differ in which of the following?
the r group
At which step of chemical evolution did life become possible?
When a self-replicating molecule evolved
Aspartate and glutamate are two amino acids that are highly soluble in water. This is best explained by the fact that they __________.
have electrically charged side chains or R groups
During the denaturation of ribonuclease, which level of protein structure was maintained?
Only the primary protein structure was maintained.
A chemical that breaks disulfide bonds might destroy which level of protein structure?
the tertiary structure
What two functional groups are present in every amino acid?
An amino group and a carboxyl group
Protein function is dependent on its shape. Some proteins may misfold, which interferes with their normal function. Infectious disease-causing agents caused by protein misfolding are called ________.
prions
Which of the following is true of the peptide bond?
It is a covalent bond formed via a condensation reaction.
Which statement about prions is true?
Prions cause changes in the shape of normal proteins that can lead to cell death.
The four bases found in DNA are grouped into purines and pyrimidines. There are two rings containing nine atoms in purines, whereas pyrimidines have a single ring with six atoms.

One way to remember which bases are purines is that __________.
adenine and guanine have the number nine in their names and are purines; purines have nine atoms
The sequence of nitrogenous bases in an RNA and DNA strand is always written in the 5′ to 3′ direction because __________.
DNA and RNA are synthesized in this direction in cells
Which of the following makes it possible for DNA to serve as a template for DNA synthesis and for RNA synthesis?
Complementary base pairing enables DNA to serve as a template.
For nucleotides to form in the prebiotic soup, which sugar would have had to be present in abundant quantities?
ribose
Which statement correctly describes one aspect of the precise bonding between components of a nucleotide?
Nitrogen in the nitrogenous base bonds to the 1′ carbon of sugar.
Nucleotides are joined by a __________ to form the DNA and RNA polymers that function in the cell.
sugar-phosphate linkage
The sugars found in nucleotides are __________.
pentoses
Scientists recognized that to obtain evidence that life arose spontaneously at some point in history, they needed to find a molecule that was capable of carrying or storing information and was capable of self-replication.

One piece of evidence critical in proposing the RNA world hypothesis was the discovery of __________ by Sidney Altman and Thomas Cech.
ribozymes
What is a major feature of the RNA world hypothesis?
The first life-forms probably had RNA as their unit of genetic information
Nucleotides polymerize via condensation reactions. The reaction forms a new covalent bond—a phosphodiester linkage, or a phosphodiester bond—between the nucleotides, and a molecule of water is released.

Where does the phosphodiester bond connect the two nucleotides?
It connects the 3′ carbon of one nucleotide to the 5′ carbon of another.
The energy for the polymerization of nucleotides comes from __________.
the hydrolysis of phosphate groups from nucleoside triphosphates
Experiments in Bartel's laboratory have tried to generate ribozymes that can perform which of the following reactions?
RNA replication and ribonucleotide production
What is true of the hairpin structure found in some RNA molecules?
It is an example of RNA secondary structure.
What is the significance of the 2′ hydroxyl on ribose for RNA function compared to DNA, which lacks the 2′ hydroxl?
The 2′ OH increases the reactivity of RNA
Which of the following can both catalyze chemical reactions and carry information to copy itself?
RNA
The primary structure of a nucleic acid is described as __________.
a sugar-phosphate backbone and a sequence of four nitrogenous bases
The secondary structure of DNA is due primarily to __________.
hydrogen bonding between complementary bases
What occurs when adenosine triphosphate (ATP) hydrolyzes to adenosine monophosphate (AMP)?
Energy is released.
What is an important function of glycoproteins in animal cells?
Glycoproteins are important in cell-cell recognition.
Polysaccharides probably did not play an important role in the origin of life because __________.
they cannot serve as a template for replication
Which of the following carbohydrates has a structural role?
cellulose
If a monosaccharide's carbonyl group is on an internal carbon, then the monosaccharide is __________.
a ketose
_________ are enzymes that help catalyze the hydrolysis of α-glycosidic bonds in glycogen, whereas ________ are enzymes that help catalyze the hydrolysis of α-glycosidic bonds in starch.
Phosphorylases; amylases
Simple sugars can differ from one another in which of the following ways?
They can differ in the location of their carbonyl group.
Carbohydrates have a variety of functions. Which polysaccharide helps fecal material move through the intestinal tract, thus preventing constipation?
cellulose
Carbohydrates are made up of which of the following monomers?
monosaccharides
Which carbohydrate is involved in the storage of energy?
glycogen
The extensive hydrogen bonding found among parallel glucose polymers of cellulose enables it to function in plants as a(n) __________.
structural polysaccharide
Carbohydrates are important in __________.
supplying sugars found in DNA and RNA
Termites are insects known for their unusual ability to eat wood as a food source. Wood is composed of dead plant cells (mostly secondary xylem) that have thick cell walls. Almost all of the other cell components are gone. Termites cannot breakdown the cell walls because they do not possess the appropriate enzyme; however, they have symbiotic microbes in their digestive tracts that do. The microbes can breakdown the cell walls and share the components with the termite. What carbohydrate are the microbes digesting and what kind of enzyme do they need?
cellulose; an enzyme to hydrolyze β-1,4-glycosidic bonds
Which of the following statements accurately compares the different polysaccharides?
Which of the following statements accurately compares the different polysaccharides?
What is the difference between peptidoglycans, which are found in the cell walls of prokaryotes, and chitin, which are found in the exoskeletons of insects?
Parallel strands of glucosamines in chitin are cross-linked by hydrogen bonds, whereas parallel strands of peptidoglycan are linked by peptide bonds.
Disaccharides are formed by joining together two monosaccharides in condensation reactions. For example, sucrose (table sugar) is composed of glucose and fructose.

The bond formed between these monomers is called __________.
a glycosidic linkage
Which of the following statements demonstrates the relationship between structure and function?
Peptidoglycan's structure of two types of monosaccharides linked by β-1, 4-glycosidic linkages and amino acids provides strength and firmness to bacterial cell walls.
Which of the following polysaccharides contains a modified monosaccharide?
chitin
When cells need energy, reactions break down __________ in the cell and capture the released energy by synthesizing __________.
glucose; ATP
Starch and cellulose are both glucose polymers. Why can animals easily degrade starch but not cellulose?
Animals have the enzymes to degrade α-1,4-glycosidic bonds but not β-1,4-glycosidic bonds.
Which cell types have the same glycoproteins on their surfaces?
None; each cell type has distinctive glycoproteins on its surface.
The predominant form of glucose dissolved in an aqueous solution is __________.
ring configuration
Glycoproteins are important in cell-cell recognition. Where are the carbohydrate portions of these molecules normally found?
On the exterior surface of the cell membrane
Glycoproteins are an important component of cell-cell communication, including recognition and signaling. The carbohydrate portion of a glycoprotein is usually a short, branched oligosaccharide because they are diverse in geometry and composition. In the experiment investigating cell-cell recognition between egg and sperm during fertilization, what part of egg-surface glycoproteins was recognized by sperm?
carbohydrate portion
What is the major difference between amylose and amylopectin?
Amylose is a straight-chain polymer of glucose, whereas amylopectin is highly branched.
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