314 Exam 1
95. Which statement about hydrogen bonds is correct?
Hydrogen bonds determine the solubility of molecules in water
99. An amino acid that would not participate in ionic bonding?
P
97. For the following peptide: R-K-S-F-R-A-L Overall it
Positively charged
98. Ion channels can have the following properties EXCEPT:
Salt extractable
7. A general term for an enzyme that catalyzes a hydrolytic cleavage reaction is: a. Hydrolase b. ATPase c. Isomerase d. Synthase e. oxido-reductase
a. Hydrolase
82. Which of the following statements regarding membrane proteins are false? a. In transmembrane proteins that form an aqueous pore through the membrane, the pore is lined with hydrophobic amino acid side chains. b. Integral membrane proteins often precipitate (form insoluble aggregates) in aqueous solutions lacking detergents. c. Strong detergents can completely unfold both membrane and no membrane proteins. d. Some transmembrane domains have amino acids with charged amino acid side chains. e. Some hydrophobic amino acids in membrane proteins are not in contact with the lipid bilayer.
a. In transmembrane proteins that form an aqueous pore through the membrane, the pore is lined with hydrophobic amino acid side chains
30. Peptide bonds are: a. Planar b. Circular c. Tetrahedral d. Unstable e. Cis
a. Planar
69. Which of the following statements is correct? a. Some activated carrier molecules can transfer energy and chemical groups b. High-energy electrons (such as those found in the activated carriers NADH and NADPH) move faster around the atomic nucleus. c. Linking the reaction X -->Y to a second, favorable reaction Y --> Z will shift the equilibrium constant of the first reaction. d. Cold-blooded animals have an energetic disadvantage because they give less heat to the environment than warm-blooded animals do. This slows their ability to make ordered macromolecules. e. A partially oxidized carbon atom has a somewhat larger diameter than a more reduced one.
a. Some activated carrier molecules can transfer energy and chemical groups
16. A strain of bacteria secretes a toxin that can lyse human red blood cells. You are able to partially purify the toxin and find that it is a small protein. Furthermore, the toxin is capable of rendering liposomes made of pure phospholipids permeable to many different ions. What type of protein is the bacterial toxin likely to be? a. a beta-barrel protein b. a protease. c. a protein containing a single hydrophobic alpha helix. d. a flippase. e. An enzyme that adds carbohydrate groups to lipids.
a. a beta-barrel protein
6. Proteins can be modified by reaction with acetate which results in the addition of an acetyl group to lysine side chains as shown in the Figure below. The bond indicated in the acetylated lysine side chain is most like: a. a peptide bond b. a phosphoester bond c. a phosphoanhydride bond. d. an ester. e. a hydrogen bond
a. a peptide bond.
90. The energy input required to initiate an energetically favorable reaction is called the: a. activation energy. b. kinetic energy. c. free energy. d. potential energy. e. chemical bond energy.
a. activation energy
74. A helical structure: a. can form either within a single large molecule or from an assembly of separate molecules. b. can form only by joining together a string of identical protein molecules. c. has to have free ends on each side. d. will contain two, three, four, or some other exact number of subunits per each turn of the helix. e. that is right-handed if viewed from one end will appear to be left-handed if viewed from its other end.
a. can form either within a single large molecule or from an assembly of separate molecules.
49. An enzyme can increase the rate of conversion of substrate (S) to product (P) for the reaction depicted below by: a. decreasing a b. decreasing b and c by the same amount. c. decreasing a and b by the same amount. d. decreasing c. e. decreasing b.
a. decreasing a
68. Carbon atoms CANNOT: a. form both covalent and ionic bonds b. form ring structures. c. form chains of virtually unlimited size. d. form double bonds. e. form four covalent bonds to other atoms.
a. form both covalent and ionic bonds
50. Forces that determine the folding of a macromolecule into distinct shape include all of the following except: a. magnetic interactions b. hydrogen bonds c. van der Waals forces d. hydrophobic interactions e. ionic interactions
a. magnetic interactions
11. Secondary structures that are found in proteins include all of the following EXCEPT: a. peptide bonds b. omega turn c. alpha helix d. beta barrel e. beta sheet
a. peptide bonds
8. The plasma membrane of an animal cell is symmetric with regard to: a. the distribution of cholesterol in each half of the lipid bilayer b. the orientation of membrane proteins in the lipid bilayer. c. the distribution of glycolipids in the lipid bilayer. d. the distribution of different phospholipids in each half of the lipid bilayer. e. All of the above
a. the distribution of cholesterol in each half of the lipid bilayer
60. Living organisms require a continual supply of energy to exist because: a. they are creating order out of disorder inside their cells b. they convert it into heat energy which powers biosynthetic reactions. c. they are closed systems isolated from the rest of the universe. d. they are defying the laws of thermodynamics. e. they are causing the entropy in the universe to decrease.
a. they are creating order out of disorder inside their cells
57. Van der Waals attractions and hydrogen bonds are similar in that a. they both are short range interactions that only come into play when molecules are close b. they both involve ionic interactions c. they both involve polar bonds d. they both require specific groups to attract e. they both involve chelated metals
a. they both are short range interactions that only come into play when molecules are close
73. All of the following statements about channel proteins are true EXCEPT: a. they can move ions up an electrochemical gradient b. they move ions at faster rates than carrier proteins. c. they are integral membrane proteins. d. they fluctuate between open and closed states. e. they might have amphipathic transmembrane segments.
a. they can move ions up an electrochemical gradient
33. Which of the following statements about enzymes are correct? a. Catalysis of an energetically unfavorable reaction by an enzyme will enable that reaction to occur. b. An enzyme can direct a molecule along a particular reaction pathway. c. An enzyme can catalyze many chemically different reactions. d. An enzyme can bind to many structurally unrelated substrates. e. Enzymes are permanently altered after catalyzing a reaction.
b. An enzyme can direct a molecule along a particular reaction pathway.
77. In which of the following reactions does the underlined atom undergo an oxidation? a. Cl Cl- b. CH3CHO CH3COOH c. CH3CH2OH CH3CHO d. CH2=CH2 CH3CH3 e. Na+ Na
b. CH3CHO CH3COOH
32. Which of the following statements is true? a. Enzymes are always comprised of protein. b. Enzymes reduce the activation energy of a reaction. c. Enzymes are able to catalyze reactions that decrease the entropy of the universe. d. Enzymes must go through covalent changes themselves to catalyze the reaction. e. Functional enzymes are heteromultimeric.
b. Enzymes reduce the activation energy of a reaction.
20. Molecules that cannot diffuse through a lipid bilayer include: a. CO2 b. Glucose c. O2 d. Benzene e. N2
b. Glucose
65. An amphipathic molecule is characterized by a. Being entirely hydrophobic b. Having both a hydrophobic and a hydrophilic end c. Having both a charged end and an uncharged polar end d. Being entirely hydrophilic e. Being insoluble
b. Having both a hydrophobic and a hydrophilic end
41. A bacterium is suddenly expelled from a warm human intestine into the cold world outside. Which of the following adjustments might the bacterium make to maintain the same level of membrane fluidity? a. Increase the length of the hydrocarbon tails in its membrane phospholipids b. Increase the proportion of unsaturated hydrocarbon tails in its membrane phospholipids. c. Increase the proportion of hydrocarbon tails with no double bonds in its membrane phospholipids. d. Increase the amount of cholesterol in the membrane. e. Decrease the amount of glycolipids in the membrane.
b. Increase the proportion of unsaturated hydrocarbon tails in its membrane phospholipids.
91. Which of the following CANNOT be a reason that cells use enzymes rather than heat to increase the rate of biochemical reactions? a. Reactions cannot be coupled without enzymes. b. No organism can live at a temperature higher than 40 degrees centigrade. c. The temperature increase required to speed up a reaction by an appreciable extent is often huge. d. An enzyme catalyzes just one or a small number of different reactions; heat would affect all the reactions in a cell. e. Enzymes can accelerate reactions to a much greater extent than can heat.
b. No organism can live at a temperature higher than 40 degrees centigrade.
66. Which of the following are the same in all atoms of an element? a. Mass. b. Number of protons c. Atomic weight. d. Number of neutrons. e. Number of neutrons plus protons
b. Number of protons
89. Which of the following processes must be coupled to an energetically favorable reaction in order to occur? a. Formation of a bilayer from phospholipids in water. b. Polymerization of amino acids into polypeptides. c. Conversion of glucose to carbon dioxide and water. d. The hydrolysis of ATP. e. Conversion of protein into amino acids.
b. Polymerization of amino acids into polypeptides.
15. Which of the following statements are false? a. Binding between protein and ligand generally involves noncovalent bonds. b. Proteins are designed to bind their ligands as tightly as possible c. Changes in the amino acid sequence of a protein can decrease binding to a ligand, even if the amino acid affected by the change does not lie in the binding site for the ligand. d. Many proteins can bind to more than one ligand e. All protein molecules function by binding specifically to other molecules.
b. Proteins are designed to bind their ligands as tightly as possible
4. Which of the following elements is least abundant in living organisms? a. Carbon. b. Sulfur. c. Nitrogen. d. Oxygen. e. Hydrogen.
b. Sulfur.
10. The possible effects of adding sugars to a protein include all of the following EXCEPT: a. Sugar moieties spread out in aqueous solution, maximizing H-bonding. b. The hydrophobic nature of sugars reduces the tendency of a protein to aggregate. c. Addition of sugars provides molecular diversity to proteins d. Glycosylation protects a protein from degradation. e. Addition of sugars may regulate protein/receptor interactions
b. The hydrophobic nature of sugars reduces the tendency of a protein to aggregate.—should say hydrophilic
79. Which of the following statements about hydrogen bonds are true? a. They are weak bonds only formed in the presence of water. b. They are weak bonds involved in maintaining the 3-D structure of macro-molecules. c. They are weak bonds formed between nonpolar groups. d. They are weak bonds formed between hydrocarbons in water. e. They are weak covalent bonds that are easily disrupted by heat
b. They are weak bonds involved in maintaining the 3-D structure of macro-molecules.
18. What are the advantages of membranes in a cell? a. They are only made up of one kind of molecule. b. They compartmentalize the cell. c. They don't let anything pass through d. They are found in both bacteria and eukaryotes. e. They give the cell its shape
b. They compartmentalize the cell
13. Which of the following statements about proteins are true? a. Most proteins contain more than 2000 amino acids. b. Two proteins having similar amino acid sequences will often have similar shapes c. The detailed three-dimensional structure of a protein can usually be determined by electron microscopy. d. The three-dimensional structure of a protein can usually be predicted from knowledge of its amino acid sequence. e. Proteins containing fewer than 100 amino acids cannot fold into stable structures.
b. Two proteins having similar amino acid sequences will often have similar shapes
19. Three phospholipids X, Y, and Z are distributed in the plasma membrane as indicated below. For which of these phospholipids does a flippase probably exist? a. X only. b. X and Y c. X and Z. d. Y and Z. e. Z only.
b. X and Y
61. H bonds can form a. between two hydrogens bound to a carbon atoms b. between a nitrogen atom and a hydrogen bound to an oxygen atom c. between a nitrogen atom and a hydrogen bound to a carbon atom d. between a sulfur atom and a nitrogen atom e. between an oxygen atom and a nitrogen atom
b. between a nitrogen atom and a hydrogen bound to an oxygen atom
25. Which of the following statements describe the typical biomembrane: a. all lipids and proteins in the biomembrane are equally mobile b. it may include different kinds of lipid molecules c. the lipid molecules are attached to each other through covalent bonds d. it contains a hydrophilic core e. it is a symmetrical structure
b. it may include different kinds of lipid molecules
22. Atoms form covalent bonds with each other by: a. attraction of positive and negative charges. b. sharing electrons. c. sharing protons. d. transferring electrons from one atom to the other. e. sharing neutrons.
b. sharing electrons.
26. The generation and maintenance of a membrane potential depends on all of the following EXCEPT: a. ATP. b. voltage-regulated ion channels. c. a selectively permeable membrane. d. active pumping of the permeant ions. e. passive diffusion.
b. voltage-regulated ion channels.
2. You are measuring the effect of temperature on the rate of an enzyme-catalyzed reaction. If you plot reaction rate against temperature, which of the graphs (1, 2, 3, or 4) would you expect your plot to resemble? a. none of the above b. 4 c. 1 d. 2 e. 3
c. 1—has a maximum optimum temperature
93. The Ca2+ pumps in the plasma membrane and the endoplasmic reticulum are examples of: a. Antiports b. Symports c. ATP-driven pumps d. coupled transporters e. passive carrier proteins
c. ATP-driven pumps
31. Which of the following statements is false? a. The active site of an enzyme usually occupies only a small fraction of the surface. b. Catalysis by some enzymes involves the formation of a covalent bond between an amino acid side chain and a substrate molecule. c. An enzyme must have both beta-sheets and alpha helices. d. Allosteric enzymes have two or more binding sites. e. An enzyme is unchanged at the end of the reaction.
c. An enzyme must have both beta-sheets and alpha helices.
51. Predict which of the following organisms will have the highest percentage of unsaturated phospholipids in their membranes. a. Thermophilic bacterium b. Human being c. Antarctic fish d. Desert snake e. Polar bear
c. Antarctic fish—coldest environment, needs to keep membranes fluid
86. The membrane potential of a typical animal cell favors the inward flux of: a. ATP. b. Cl- c. Ca2+. d. water. e. glucose.
c. Ca2+
70. Which of the following statements are true? a. Resting cells do not produce any heat. b. Enzymes that couple unfavorable reactions to favorable reactions cause a decrease in total entropy. c. Life is a thermodynamically spontaneous process. d. The only processes that can occur to any significant degree are those that decrease the disorder in the universe. e. Growing cells release less heat to the environment than resting cells because they use more energy.
c. Life is a thermodynamically spontaneous process.
40. Which of the following statements regarding lipid membranes are true? a. Phospholipids will spontaneously form liposomes in nonpolar solvents. b. A solution of pure fatty acids forms a lipid bilayer in a polar solvent. c. Membrane lipids move laterally within their own layer. d. Membrane lipids frequently move between one layer of the bilayer and the other. e. The preferred form of a lipid bilayer in water is a flat sheet with exposed edges
c. Membrane lipids move laterally within their own layer.
56. Which of the following movements can a membrane protein make by lateral diffusion through the lipid bilayer? a. Movement from the outer nuclear membrane to the inner nuclear membrane. b. none of the above. c. Movement from the outer nuclear membrane to the endoplasmic reticulum. d. Movement from the outer mitochondrial membrane to the inner mitochondrial membrane e. Movement from the apical plasma membrane to the basal plasma membrane in a gut epithelial cell
c. Movement from the outer nuclear membrane to the endoplasmic reticulum
27. In a typical animal cell, which of the following types of transport occurs through a channel protein? a. Movement of glucose out of a starved cell. b. Movement of amino acids into a cell. c. Movement of Na+ into a cell. d. Movement of Na+ out of a cell. e. Movement of glucose into a starved cell.
c. Movement of Na+ into a cell.
92. An action potential depends directly on all of the following EXCEPT: a. activation of voltage-dependent ion channels activated of voltage-gated Na+ channels b. chemical gradients of permeant ions. c. activation of the Na+-K+ ATPase. d. inactivation of voltage-dependent ion channels. e. a rapid change in membrane potential.
c. activation of the Na+-K+ ATPase.
14. Which of the following statements are correct? a. Since the structure of a protein is determined solely by its amino acid sequence, a genetically engineered protein of the reverse sequence would have the same structure as the original protein. b. A alpha sheet can contain up to five strands, but no more. c. amino acids behave as acids and bases. d. The tertiary structure is the localized folding arrangement of a polypeptide chain. e. Alpha helices are depicted as flattened arrows on a ribbon diagram.
c. amino acids behave as acids and bases.
1. The alpha helix and beta sheet are found in many different proteins because they are formed by: a. hydrogen bonding between the amino acid side chains most commonly found in proteins. b. disulfide bonds. c. hydrogen bonding between atoms of the polypeptide backbone d. noncovalent interactions between amino acid side chains and the polypeptide backbone. e. ionic interactions between charged amino acid side chains
c. hydrogen bonding between atoms of the polypeptide backbone.
80. Life is thermodynamically possible because living things: a. carry out energetically favorable reactions only. b. reproduce themselves. c. release heat to the environment. d. can carry out a chain of reactions that is energetically unfavorable. e. increase the degree of order in the universe.
c. release heat to the environment.
36. For a reaction to occur spontaneously a. ΔG must be positive b. the reaction must be energetically unfavorable c. the products must have a lower energy than the reactants d. an input of energy must be provided. e. an enzyme must be present.
c. the products must have a lower energy than the reactants
5. Amino acid(s) that can be phosphorylated include: a. methionine b. tryptophan c. threonine d. all of the above e. none of the above
c. threonine
62. An ionic bond between two atoms is formed as a result of: a. sharing of electrons. b. loss of a proton from one atom. c. transfer of electrons from one atom to the other. d. loss of a neutron from one atom. e. loss of electrons from both atoms.
c. transfer of electrons from one atom to the other
28. Which of the following is NOT a benefit of using a chain of neurons and chemical synapses rather than a direct connection between the site of stimulus and the site of response? a. Chemical synapses allow neurons to receive and integrate input from more than one source. b. Modification of different ion channels at synapses can be used to generate memory on the cellular level. c. Use of chemical synapses increases the variety of messages the presynaptic cell can send to the postsynaptic cell. d. Diffusion of small molecules is more rapid than propagation of an electric signal; thus the signal is speeded up by having more synapses. e. Each chemical
d. Diffusion of small molecules is more rapid than propagation of an electric signal; thus the signal is speeded up by having more synapses.
44. The most abundant intracellular cation is: a. Na+ b. Ca2+ c. H+ d. K+ e. positively charged macromolecules
d. K+
48. A general term for an enzyme that catalyzes the addition of a phosphate group to molecules is: a. Protease b. oxido-reductase c. Phosphatase d. Kinase e. ATPase
d. Kinase—catalyzes the addition of phosphate groups to molecules
3. Which of the following might act as an ER "signal sequence"? a. NH3+-M- A-N-L- L-H-A-L-V-R-R-R-R-L-V-G-A-L-V b. NH3+-M- A-N-L- L-H-R-L-D-A-Q-S-K-L-S-S c. ------KKKKKKK---- d. NH3+-M- A-N-L- L-H-A-L-V-A-I-G-A-L-V-G-A-L-V----- e. ----KDEL ---- ER
d. NH3+-M- A-N-L- L-H-A-L-V-A-I-G-A-L-V-G-A-L-V----- extended block of hydrophobic amino acids with N Terminus present (Hydrophobic = A, G, V, L, I, P, F, M, W, C)these are also nonpolar
88. Which of the following statements is true? a. A protein chain ends in a free amino group at the C-terminus. b. The sequence of the atoms in the polypeptide backbone varies between different proteins c. Peptide bonds are the only covalent bonds that can link together two amino acids in proteins d. Nonpolar amino acids tend to be found in the interior of proteins. e. The polypeptide backbone of some proteins is branched.
d. Nonpolar amino acids tend to be found in the interior of proteins.
52. Which of the following statements regarding the fatty acid tails of phospholipids are false? a. Most membrane phospholipids have one fully saturated tail. b. Saturated phospholipid tails pack more tightly against each other than do unsaturated tails. c. Fatty acid tails vary in length. d. Phospholipids with unsaturated tails make the bilayer more fluid because the tails contain fewer hydrogens and thus form fewer hydrogen bonds with each other. e. Phospholipid tails in a membrane can interact with each other via van der Waals interactions.
d. Phospholipids with unsaturated tails make the bilayer more fluid because the tails contain fewer hydrogens and thus form fewer hydrogen bonds with each other.—they don't hydrogen bond with each other
9. An amino acids you would expect to more frequently find on the outside of a folded globular protein would be: a. I b. L c. A d. R e. V
d. R—arginine, Arg; basic, polar
78. After looking at the Figure below, which of the following pairs of atoms do you expect to be able to form double bonds with each other? a. C and Cl. b. C and H. c. Mg and Ca. d. S and O. e. He and O
d. S and O.
64. Based on what you know about the properties of water, which of the following statements about methanol (CH3OH) are true? a. Methanol molecules form more hydrogen bonds than water molecules do. b. Methanol is a more cohesive liquid than water. c. The boiling point of methanol is higher than that of water. d. Salts such as NaCl are less soluble in methanol than in water. e. Methanol has a higher surface tension than water.
d. Salts such as NaCl are less soluble in methanol than in water.
21. Which of the following is not true about K+ channels? a. The amphipathic S4 domain senses the change in membrane potential and rotates within the membrane, resulting in an allosteric change of the channel from closed to open configuration. b. K+ channels are responsible for repolarization of the membrane. c. In the inactivated state, a domain of the channel called the "inactivation peptide" binds to the opening to block it, in what is called a "ball and chain" model. d. Since Na+ ions are smaller than K+ ions but also have a single positive charge, they in theory would be able to interact with the carbonyls and also pass through the K+ channel but do not because of the chemical gradient in the cell. e. Carbonyl groups in the
d. Since Na+ ions are smaller than K+ ions but also have a single positive charge, they in theory would be able to interact with the carbonyls and also pass through the K+ channel but do not because of the chemical gradient in the cell.
72. Which of the following statements is not true? a. At the resting membrane potential, ion channels fluctuate between open and closed conformations. b. Facilitated transport does not require energy. c. Passive transport can be mediated by conformational change of a membrane protein. d. The facilitated diffusion of glucose across the cell membrane depends on membrane proteins called gated channels. e. Absorption of a photon of light can drive active transport
d. The facilitated diffusion of glucose across the cell membrane depends on membrane proteins called gated channels.
81. Four samples of cells have membranes containing a uniform distribution of a fluorescently labeled phospholipid (sample 1) and three fluorescently labeled membrane proteins X, Y, and Z (samples 2-4), respectively. An intense beam of light is shone on each sample. The light beam destroys the fluorescent label in the illuminated area, but the intensity of fluorescence in the area recovers over time, as bleached molecules diffuse away and unbleached molecules diffuse in. The results of this experiment are shown below. Which of the following interpretations are INCONSISTENT with these results? a. X is a small freely diffusing protein. b. Y is a large freely diffusing protein. c. none of the above d. X and Y are part of the same large protein complex. e. Z is bound to a component of the cell cortex.
d. X and Y are part of the same large protein complex
84. Gut intestinal epithelial cells, as illustrated below, have several characteristics essential for their function, including: a. a Na+-K+ pump that pumps Na+ into the cell to maintain the Na+ electrochemical gradient. b. free diffusion of glucose carriers throughout the cell so glucose can be both brought into the cell from the gut and flow out of the cell to the extracellular fluid. c. a glucose carrier protein on the basal membrane that uses active transport to transfer glucose to the extracellular fluid d. a glucose carrier protein on the apical membrane that uses active transport to bring sugar into the cell. e. microvilli on their basal membranes, to increase the surface area for more efficient absorption of glucose
d. a glucose carrier protein on the apical membrane that uses active transport to bring sugar into the cell.
75. Disulfide bonds: a. are formed by the cross-linking of methionine residues b. rarely form in extracellular proteins c. are formed mainly in proteins that are retained within the cytosol. d. can be broken by reduction (for example, by b-mercaptoethanol) e. stabilize but do not change a protein's final conformation
d. can be broken by reduction (for example, by b-mercaptoethanol)
54. During an action potential, a sodium ion channel goes through the following states: a. closed -> inactivated -> open -> closed b. open -> inactivated -> closed -> open c. inactivated -> open -> closed -> inactivated d. closed -> open -> inactivated -> closed e. inactivated -> closed -> open -> inactivated
d. closed -> open -> inactivated -> closed
34. Energetically favorable reactions are those that: a. decrease the entropy of a system. b. increase the free energy of a system. c. have a positive ∆G. d. decrease the free energy of a system. e. create order in a system.
d. decrease the free energy of a system.
83. The lipid bilayer is held together primarily by: a. covalent bonding between the ends of phospholipid tails in opposite layers. b. covalent bonding between membrane lipids. c. hydrogen-binding between the phospholipid tails d. repulsion between the phospholipid tails and water. e. hydrogen-bonding between the head groups of phospholipids.
d. repulsion between the phospholipid tails and water.
87. The equilibrium constant for the binding of a protein to its ligand can depend on all of the following EXCEPT: a. the exact fit of the binding site to the ligand. b. the temperature. c. the pH d. the concentration of the ligand. e. the number of noncovalent bonds formed between the protein and the ligand.
d. the concentration of the ligand.
45. Which statement below about the sodium-potassium pump is false? a. moves 2 K+ ions into the cell for every 3 Na+ ions moved out of the cell b. hydrolyses ATP c. undergoes allosteric change d. uses the electrochemical gradient of Na+ to pump K+ into the cell e. has an Na+ binding site on the intracellular domain and a K+ binding site on the extracellular domain
d. uses the electrochemical gradient of Na+ to pump K+ into the cell
85. The action potential travels in one direction because: a. depolarization of the membrane causes voltage-gated K+ channels to open. b. voltage-gated Na+-channels spend less time in the open conformation when the membrane returns to the resting potential. c. the K+ leak channels allow K+ to flow out, restoring the membrane to resting potential. d. voltage-gated Na+ channels adopt a transitory inactive conformation after being opened. e. The Na+-K+ pump restores the concentrations of Na+ and K+ to their original levels.
d. voltage-gated Na+ channels adopt a transitory inactive conformation after being opened.
37. A stretch of amino acids you might expect to find in a transmembrane domain would be: a. E-G-T-Y-H-W-D-S-A-N-M-E-L-W-D-T-Y-I-S-A b. P-G-G-A-L-P-S-V-T-M-F-L-N-V-S-W-H-P-S-N c. G-N-Q-A-L-R-Y-T-W-K-N-K-W-I-L-R-Q-A-G-F d. K-K-L-V-A-A-V-L-I-K-L-V-A-A-V-V-I-L-R-R e. A-M-G-I-I-V-M-L-L-A-S-G-L-A-L-V-I-A-V-M
e. A-M-G-I-I-V-M-L-L-A-S-G-L-A-L-V-I-A-V-M
67. Which of the following statements about the basic chemistry of cells are true? a. All cells contain exactly the same proteins. b. All organisms contain the same genes. c. All proteins are constructed from the same 22 amino acids. d. All of the above. e. All genetic instructions in cells are stored in DNA
e. All genetic instructions in cells are stored in DNA
17. Peripheral membrane proteins can be attached to the membrane by all of the following except: a. Electrostatic interactions with phospholipids b. An isoprene (farness) tail attached to a Coax box at its C-terminus. c. A GPI (glycophosphatidylinositol) tail attached to its C-terminus. d. Partial penetration of the lipid bilayer. e. Association with microtubules
e. Association with microtubules.
53. Which statement below is true? a. Carrier proteins allow solutes to cross a membranes at much faster rates than do channel proteins. b. A symport would function as an antiport if its orientation in the membrane were reversed (i.e., if the portion of the molecule normally exposed to the cytosol faced outside the cell instead).transports both solutes in the same direction, antiport transports solutes in opposite directions of each other c. The plasma membrane is highly impermeable to all charged molecules. d. Channel proteins must first bind to solute molecules before they can select those that they will allow to pass. e. Certain H+ pumps are fueled by light energy
e. Certain H+ pumps are fueled by light energy
63. Which of the following pairs of elements are likely to form ionic bonds? Use the following Figure if necessary a. Carbon and oxygen b. Sulfur and hydrogen c. Hydrogen and hydrogen. d. Carbon and chlorine e. Magnesium and chlorine.
e. Magnesium and chlorine.
76. Which of the following statements about amino acids are true? a. Not all amino acids have R groups. b. D- and L-amino acids are found in proteins c. Twenty-two amino acids are commonly found in proteins. d. Most of the amino acids used in protein biosynthesis have charged side chains. e. Proline is formally not an amino acid but an imino acid
e. Proline is formally not an amino acid but an imino acid
47. Carrier proteins can be classified into different types listed below EXCEPT: a. Uniporters b. Symporters c. Antiporters d. Coupled transporters e. Quasiporters
e. Quasiporters
39. Which of the following statements is not correct about lipids in a lipid bilayer? a. lipids rotate rapidly around their long axis b. lipids rapidly exchange positions with respect to one another in the plane of the membrane c. lipids do not flip-flop readily from one lipid monolayer to the other d. hydrogen bonds are continually broken and re-formed between lipid head groups and water molecule e. The composition of the phospholipid heads is the same on both inner and outer leaves of the lipid bilayer.
e. The composition of the phospholipid heads is the same on both inner and outer leaves of the lipid bilayer. -it is asymmetrical
59. Where does the most new membrane synthesis take place in a eukaryotic cell? a. The Golgi apparatus. b. The plasma membrane. c. Cytoplasmic membrane vesicles. d. The mitochondria. e. The endoplasmic reticulum.
e. The endoplasmic reticulum.
94. The common feature of alpha helices and beta sheets that make them universal building blocks for proteins is a. all of the side-chains are involved in ionic interactions b. they are amphipathic c. they start with an initiating methionine d. they can be phosphorylated e. all of the N-H and C=O groups are engaged in hydrogen bonds
e. all of the N-H and C=O groups are engaged in hydrogen bonds
46. Ion channels: a. only open in response to a signal of some kind. b. require input of energy in order to function. c. have no limit to the rate at which they can transport ions. d. can transport both positive and negative ions through the same channel. e. allow passage of ions in both directions.
e. allow passage of ions in both directions.
55. All of the proteins listed below are enzymes EXCEPT: a. nuclease b. polymerase c. ATPase d. kinase e. antibody
e. antibody
71. Assembling the individual enzymes required for a multistep process into a protein machine is likely to increase the efficiency with which the entire process is carried out in all of the following ways EXCEPT: a. by coordinating the regulation of the individual enzymes. b. by increasing the rate at which the individual enzymes encounter their substrates. c. by coordinating the movement of the enzymes. d. by ordering the reactions sequentially. e. by increasing the Vmax of the individual enzymes.
e. by increasing the Vmax of the individual enzymes.
35. A common means of providing energy to an energetically unfavorable reaction in a cell is by: a. generation of a higher temperature by the cell. b. transfer of a phosphate group from the substrate to ADP. c. enzyme catalysis of the reaction. d. coupling of the synthesis of ATP to the reaction. e. coupling of ATP hydrolysis to the reaction.
e. coupling of ATP hydrolysis to the reaction.
38. The specificity of macromolecular assembly is influenced by multiple weak interactions provided by all of the following except: a. hydrogen bonding b. van der Waals interactions c. ionic interactions d. hydrophobic interactions e. disulfide bonds
e. disulfide bonds—not weak
42. New membrane synthesis occurs by: a. the spontaneous aggregation of free phospholipids into a new bilayer in the aqueous environment of the cell. b. incorporation of phospholipids into both faces of a preexisting membrane by enzymes attached to each face. c. incorporation of phospholipids into one face of a preexisting membrane and their random redistribution to both faces by flippases. d. de novo biosynthesis of phospholipids within a preexisting membrane by enzymes. e. incorporation of phospholipids into one face of a preexisting membrane and their specific redistribution by flippases.
e. incorporation of phospholipids into one face of a preexisting membrane and their specific redistribution by flippases.
58. The energy required by a human cell to grow and reproduce is provided by: a. generation of heat. b. its biosynthetic reactions. c. the generation of order inside it. d. its anabolic metabolism. e. its catabolic metabolism
e. its catabolic metabolism
23. Which of the following reactions will occur only if coupled to a second, energetically favorable reaction? a. ATP --> ADP + Pi b. protein --> amino acids c. ADP --> AMP + Pi d. glucose + O2 --> CO2 + H2O e. nucleoside triphosphates --> DNA
e. nucleoside triphosphates --> DNA—alone this is energetically unfavorable, couple it to make it favorable
12. All known proteins in cells adopt a stable conformation because: a. any chain of amino acids can fold up into only one stable conformation. b. they are complexed with other molecules that keep them in that one particular conformation. c. once folded, proteins are surrounded by a cage of water molecules that keep them in that one particular conformation. d. chaperone proteins prevent the protein from adopting a preferred unstable conformation. e. protein chains that can adopt many different conformations have been weeded out by natural selection.
e. protein chains that can adopt many different conformations have been weeded out by natural selection.
24. Which of the following reactions are energetically favorable? a. base + sugar + phosphate --> nucleotide b. amino acid + amino acid --> peptide c. CO2 + H2O --> sugar d. N2 + H2 --> ammonia e. sucrose --> CO2 + H2O
e. sucrose --> CO2 + H2O—large to small
29. The polar property of water is important for all of the following EXCEPT: a. the hydration shells of free ions. b. the clustering of hydrophobic residues of a polypeptide in solution. c. the ionization of water. d. the hydrogen bond formation between neighboring water molecules. e. the contraction of volume when water freezes.
e. the contraction of volume when water freezes
43. All of the following are characteristic of some integral membrane proteins EXCEPT: a. they often have one or more -helical transmembrane segments. b. they might be amphipathic. c. they might diffuse freely in the lipid bilayer. d. they might be tethered in the lipid bilayer. e. they often can be extracted from the membrane with high salt.
e. they often can be extracted from the membrane with high salt.
96. Which of the following statements about import of proteins into mitochondria are true
mitochondrial inner matrix proteins are translocated across the inner and outer membranes simultaneoulsy
