5) The primary function of polysaccharides attached to the glycoproteins and glycolipids of animal cell membranes is

A) to facilitate diffusion of molecules down their concentration gradients. B) to actively transport molecules against their concentration gradients. C) to maintain the integrity of a fluid mosaic membrane. D) to maintain membrane fluidity at low temperatures. E) to mediate cell-to-cell recognition.

E) to mediate cell-to-cell recognition.

6) A protein that spans the phospholipid bilayer one or more times is

A) a transmembrane protein. B) an integral protein. C) a peripheral protein.D) an integrin. E) a glycoprotein.

A) a transmembrane protein.

7) Why are lipids and proteins free to move laterally in membranes?

A) The interior of the membrane is filled with liquid water.

B) Lipids and proteins repulse each other in the membrane.

C) Hydrophilic portions of the lipids are in the interior of the membrane.

D) There are only weak hydrophobic interactions in the interior of the membrane.

E) Molecules such as cellulose can pull them in various directions.

D) There are only weak hydrophobic interactions in the interior of the membrane.

8) What kinds of molecules pass through a cell membrane most easily?

A) large and hydrophobic B) small and hydrophobic C) large polar D) ionic E) monosaccharides such as glucose

B) small and hydrophobic

9) Which of the following is a characteristic feature of a carrier protein in a plasma membrane?

A) It is a peripheral membrane protein. B) It exhibits a specificity for a particular type of molecule. C) It requires the expenditure of cellular energy to function. D) It works against diffusion. E) It has few, if any, hydrophobic amino acids.

B) It exhibits a specificity for a particular type of molecule.

10) Which of the following statements is correct about diffusion?

A) It is very rapid over long distances. B) It requires an expenditure of energy by the cell. C) It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration. D) It is an active process in which molecules move from a region of lower concentration to one of higher concentration. E) It requires integral proteins in the cell membrane.

C) It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.

11) Water passes quickly through cell membranes because

A) the bilayer is hydrophilic. B) it moves through hydrophobic channels. C) water movement is tied to ATP hydrolysis. D) it is a small, polar, charged molecule. E) it moves through aquaporins in the membrane.

E) it moves through aquaporins in the membrane.

12) Mammalian blood contains the equivalent of 0.15 M NaCl. Seawater contains the equivalent of 0.45 M NaCl. What will happen if red blood cells are transferred to seawater?

A) Water will leave the cells, causing them to shrivel and collapse. B) NaCl will be exported from the red blood cells by facilitated diffusion. C) The blood cells will take up water, swell, and eventually burst. D) NaCl will passively diffuse into the red blood cells. E) The blood cells will expend ATP for active transport of NaCl into the cytoplasm.

A) Water will leave the cells, causing them to shrivel and collapse.

13) Which of the following membrane activities require energy from ATP hydrolysis?

1. A) facilitated diffusion of chloride ions across the membrane through a chloride channel
2. B) movement of water into a cell C) Na+ions moving out of a mammalian cell bathed in physiological saline D) movement of glucose molecules into a bacterial cell from a medium containing a higher concentration of glucose than inside the cell E) movement of carbon dioxide out of a paramecium

C) Na+ ions moving out of a mammalian cell bathed in physiological saline

14) Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport mechanism is most probably functioning in the intestinal cells?

A) simple diffusion B) phagocytosis C) active transport pumps D) exocytosis E) facilitated diffusion

E) facilitated diffusion

15) Ions diffuse across membranes through specific ion channels

A) down their chemical gradients. B) down their concentration gradients. C) down the electrical gradients. D) down their electrochemical gradients. E) down the osmotic potential gradients.

D) down their electrochemical gradients.

16) White blood cells engulf bacteria through what process?

A) exocytosis B) phagocytosis C) pinocytosis D) osmosis E) receptor-mediated exocytosis

B ) phagocytosis

17) Familial hypercholesterolemia is characterized by which of the following?

A) defective LDL receptors on the cell membranes B) poor attachment of the cholesterol to the extracellular matrix of cells C) a poorly formed lipid bilayer that cannot incorporate cholesterol into cell membranes D) inhibition of the cholesterol active transport system in red blood cells

E) a general lack of glycolipids in the blood cell membranes

A) defective LDL receptors on the cell membranes

18) The difference between pinocytosis and receptor-mediated endocytosis is that

A) pinocytosis brings only water molecules into the cell, but receptor-mediated endocytosis brings in other molecules as well. B) pinocytosis increases the surface area of the plasma membrane whereas receptor-mediated endocytosis decreases the plasma membrane surface area. C) pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity. D) pinocytosis requires cellular energy, but receptor-mediated endocytosis does not. E) pinocytosis can concentrate substances from the extracellular fluid, but receptor-mediated endocytosis cannot.

C) pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity.

20) The CFTR protein belongs to what category of membrane proteins?

A) gap junctions B) aquaporins C) electrogenic ion pumps D) cotransporters E) hydrophilic channels

C) electrogenic ion pumps

21) A patient has had a serious accident and lost a lot of blood. In an attempt to replenish body fluids, distilled water–equal to the volume of blood lost–is transferred directly into one of his veins. What will be the most probable result of this transfusion?

A) It will have no unfavorable effect as long as the water is free of viruses and bacteria.

B) The patient's red blood cells will shrivel up because the blood fluid has become hypotonic compared to the cells. C) The patient's red blood cells will swell because the blood fluid has become hypotonic compared to the cells. D) The patient's red blood cells will shrivel up because the blood fluid has become hypertonic compared to the cells. E) The patient's red blood cells will burst because the blood fluid has become hypertonic compared to the cells.

C) The patient's red blood cells will swell because the blood fluid has become hypotonic compared to the cells.

22) Which of the following factors would tend to increase membrane fluidity?

A) a greater proportion of unsaturated phospholipids B) a greater proportion of saturated

Phospholipids C) a lower temperature D) a relatively high protein content in the membrane

E) a greater proportion of relatively large glycolipids compared with lipids having smaller molecular masses

A) a greater proportion of unsaturated phospholipids

23) According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly

1. A) spread in a continuous layer over the inner and outer surfaces of the membrane.
2. B) confined to the hydrophobic interior of the membrane. C) embedded in a lipid bilayer.
3. D) randomly oriented in the membrane, with no fixed inside-outside polarity.
4. E) free to depart from the fluid membrane and dissolve in the surrounding solution.

C) embedded in a lipid bilayer.

24) In an HIV-infected cell producing HIV virus particles, the viral glycoprotein is expressed on the plasma membrane. How do the viral glycoproteins get to the plasma membrane?

1. A) They are synthesized on ribosomes on the plasma membrane. B) They are synthesized by ribosomes in the rough ER, and arrive at the plasma membrane in the membrane of secretory vesicles. C) They are synthesized on free cytoplasmic ribosomes, and then inserted into the plasma membrane. D) They are synthesized by ribosomes in the rough ER, secreted from the cell, and inserted into the plasma membrane from the outside. E) They are synthesized by ribosomes on the HIV viral membrane, which fuses with the plasma membrane from inside the cell.

B) They are synthesized by ribosomes in the rough ER, and arrive at the plasma membrane in the membrane of secretory vesicles.

1) Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?

A) catalysis B) metabolism C) anabolism D) dehydration E) catabolism

1. E) catabolism

2) Which of the following is most similar in structure to ATP?

A) a pentose sugar B) a DNA nucleotide C) an RNA nucleotide D) an amino acid with three phosphate groups attached E) a phospholipid

C) an RNA nucleotide

3) Which of the following statements is true about enzyme-catalyzed reactions?

A) The reaction is faster than the same reaction in the absence of the enzyme.

B) The free energy change of the reaction is opposite from the reaction that occurs in the absence of the enzyme. C) The reaction always goes in the direction toward chemical equilibrium. D) Enzyme-catalyzed reactions require energy to activate the enzyme. E) Enzyme-catalyzed reactions release more free energy than noncatalyzed reactions.

A) The reaction is faster than the same reaction in the absence of the enzyme.

4) Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's

A) entropy. B) activation energy. C) endothermic level. D) equilibrium point. E) free-energy content.

B) activation energy.

5) Which of the following statements regarding enzymes is true?

A) Enzymes increase the rate of a reaction by making the reaction more exergonic. B) Enzymes increase the rate of a reaction by lowering the activation energy barrier. C) Enzymes increase the rate of a reaction by reducing the rate of reverse reactions. D) Enzymes change the equilibrium point of the reactions they catalyze. E) Enzymes make the rate of a reaction independent of substrate concentrations.

B) Enzymes increase the rate of a reaction by lowering the activation energy barrier.

6) The active site of an enzyme is the region that

A) binds allosteric regulators of the enzyme. B) is involved in the catalytic reaction of the enzyme. C) binds noncompetitive inhibitors of the enzyme. D) is inhibited by the presence of a coenzyme or a cofactor.

B) is involved in the catalytic reaction of the enzyme.

7) According to the induced fit hypothesis of enzyme catalysis, which of the following is correct?

A) The binding of the substrate depends on the shape of the active site. B) Some enzymes change their structure when activators bind to the enzyme. C) A competitive inhibitor can outcompete the substrate for the active site. D) The binding of the substrate changes the shape of the enzyme's active site. E) The active site creates a microenvironment ideal for the reaction.

D) The binding of the substrate changes the shape of the enzyme's active site.

8) Mutations that result in single amino acid substitutions in an enzyme

A) can have no effect on the activity or properties of the enzyme. B) will almost always destroy the activity of the enzyme. C) will often cause a change in the substrate specificity of the enzyme. D) may affect the physicochemical properties of the enzyme such as its optimal temperature and pH . E) may, in rare cases, cause the enzyme to run reactions in reverse.

D) may affect the physicochemical properties of the enzyme such as its optimal temperature and pH .

9) Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?

A) denaturization of the enzyme B) allosteric inhibition C) competitive inhibition D) saturation of the enzyme activity E) insufficient cofactors

C) competitive inhibition

10) Which of the following is true of enzymes?

A) Nonprotein cofactors alter the substrate specificity of enzymes.

B) Enzyme function is increased if the 3-D structure or conformation of an enzyme is altered.

C) Enzyme function is independent of physical and chemical environmental factors such as pH and temperature.

D) Enzymes increase the rate of chemical reaction by lowering activation energy barriers.

E) Enzymes increase the rate of chemical reaction by providing activation energy to the substrate.

D) Enzymes increase the rate of chemical reaction by lowering activation energy barriers.

11) Zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. The zinc most likely functions as a(n)

A) competitive inhibitor of the enzyme. B) noncompetitive inhibitor of the enzyme. C) allosteric activator of the enzyme. D) cofactor necessary for enzyme activity. E) coenzyme derived from a vitamin.

D) cofactor necessary for enzyme activity.

12) In order to attach a particular amino acid to the tRNA molecule that will transport it, an enzyme, an aminoacyl-tRNA synthetase, is required, along with ATP. Initially, the enzyme has an active site for ATP and another for the amino acid, but it is not able to attach the tRNA. What must occur in order for the final attachment to occur?

A) The ATP must first have to attach to the tRNA. B) The binding of the first two molecules must cause a 3-D change that opens another active site on the enzyme. C) The ATP must be hydrolyzed to allow the amino acid to bind to the synthetase. D) The tRNA molecule must have to alter its shape in order to be able to fit into the active site with the other two molecules.

E) The 3' end of the tRNA must have to be cleaved before it can have an attached amino acid.

B) The binding of the first two molecules must cause a 3-D change that opens another active site on the enzyme.

13) Some of the drugs used to treat HIV patients are competitive inhibitors of the HIV reverse transcriptase enzyme. Unfortunately, the high mutation rate of HIV means that the virus rapidly acquires mutations with amino acid changes that make them resistant to these competitive inhibitors. Where in the reverse transcriptase enzyme would such amino acid changes most likely occur in drug-resistant viruses?

A) in or near the active site B) at an allosteric site C) at a cofactor binding site D) in regions of the protein that determine packaging into the virus capsid E) such mutations could occur anywhere with equal probability

A) in or near the active site

14) How does a noncompetitive inhibitor decrease the rate of an enzyme reaction?

A) by binding at the active site of the enzyme B) by changing the shape of the enzyme's active site C) by changing the free energy change of the reaction D) by acting as a coenzyme for the reaction E) by decreasing the activation energy of the reaction

B) by changing the shape of the enzyme's active site

15) The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is most precisely described as

A) metabolic inhibition. B) feedback inhibition. C) allosteric inhibition. D) noncooperative inhibition. E) reversible inhibition.

B) feedback inhibition.

16) Allosteric enzyme regulation is usually associated with

A) lack of cooperativity. B) feedback inhibition. C) activating activity. D) an enzyme with more than one subunit. E) the need for cofactors.

D) an enzyme with more than one subunit.

17) Protein kinases are enzymes that catalyze phosphorylation of target proteins at specific sites, whereas protein phosphatases catalyze removal of phosphate(s) from phosphorylated proteins. Phosphorylation and dephosphorylation can function as an on-off switch for a protein's activity, most likely through

1. A) the change in a protein's charge leading to a conformational change. B) the change in a protein's charge leading to cleavage. C) a change in the optimal pH at which a reaction will occur. D) a change in the optimal temperature at which a reaction will occur. E) the excision of one or more peptides.

A) the change in a protein's charge leading to a conformational change.

18) For the enzyme-catalyzed reaction shown in the figure, which of these treatments will cause the greatest increase in the rate of the reaction, if the initial reactant concentration is 1.0 micromolar?

1. A) doubling the activation energy needed B) cooling the reaction by 10°C C) doubling the concentration of the reactants to 2.0 micromolar D) doubling the enzyme concentration

E) increasing the concentration of reactants to 10.0 micromolar, while reducing the concentration of enzyme by 1/2

1. D) doubling the enzyme concentration

19) In the figure, why does the reaction rate plateau at higher reactant concentrations?

A) Feedback inhibition by product occurs at high reactant concentrations. B) Most enzyme molecules are occupied by substrate at high reactant concentrations. C) The reaction nears equilibrium at high reactant concentrations. D) The activation energy for the reaction increases with reactant concentration. E) The rate of the reverse reaction increases with reactant concentration.

B) Most enzyme molecules are occupied by substrate at high reactant concentrations.

20) Which curve(s) on the graphs may represent the temperature and pH profiles of an enzyme taken from a bacterium that lives in a mildly alkaline hot springs at temperatures of 70°C or higher?

A) curves 1 and 5 B) curves 2 and 4 C) curves 2 and 5 D) curves 3 and 4 E) curves 3 and 5

1. E) curves 3 and 5

21) Which temperature and pH profile curves on the graphs were most likely generated from analysis of an enzyme from a human stomach where conditions are strongly acid?

1. A) curves 1 and 4 B) curves 1 and 5 C) curves 2 and 4 D) curves 2 and 5 E) curves 3 and 4

Answer: A

A) curves 1 and 4

27) Based on this information, which of the following is correct?

A) Succinate dehydrogenase is the enzyme, and fumarate is the substrate. B) Succinate dehydrogenase is the enzyme, and malonic acid is the substrate. C) Succinate is the substrate, and fumarate is the product. D) Fumarate is the product, and malonic acid is a noncompetitive inhibitor. E) Malonic acid is the product, and fumarate is a competitive inhibitor.

C) Succinate is the substrate, and fumarate is the product.

A series of enzymes catalyze the reaction X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme.

28) What is substance X?

A) a coenzyme B) an allosteric inhibitor C) a substrate D) an intermediate E) the product

C) a substrate

29) Some bacteria are metabolically active in hot springs because

A) they are able to maintain a lower internal temperature. B) high temperatures make catalysis

unnecessary. C) their enzymes have high optimal temperatures. D) their enzymes are completely

insensitive to temperature. E) they use molecules other than proteins or RNAs as their main

catalysts.

29) Some bacteria are metabolically active in hot springs because

A) they are able to maintain a lower internal temperature. B) high temperatures make catalysis

unnecessary. C) their enzymes have high optimal temperatures. D) their enzymes are completely

insensitive to temperature. E) they use molecules other than proteins or RNAs as their main

catalysts.

C) their enzymes have high optimal temperatures.

30) If an enzyme in solution is saturated with substrate, the most effective way to obtain a faster yield of products is to

A) add more of the enzyme. B) heat the solution to 90°C. C) add more substrate. D) add an

allosteric inhibitor. E) add a noncompetitive inhibitor.

A) add more of the enzyme.

1) What is the term for metabolic pathways that release stored energy by breaking down complex molecules?

A) anabolic pathways B) catabolic pathways C) fermentation pathways D) thermodynamic pathways E) bioenergetic pathways

B) catabolic pathways

2) The molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction

1. A) gains electrons and gains potential energy. B) loses electrons and loses potential energy. C) gains electrons and loses potential energy. D) loses electrons and gains potential energy.

E) neither gains nor loses electrons, but gains or loses potential energy.

B) loses electrons and loses potential energy.

3) Which of the following statements describes the results of this reaction?

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy

1. A) C6H12O6 is oxidized and O2 is reduced. B) O2 is oxidized and H2O is reduced. C) CO2 is reduced and O2 is oxidized. D) C6H12O6 is reduced and CO2 is oxidized. E) O2 is reduced and CO2 is oxidized.

A) C6H12O6 is oxidized and O2 is reduced.

4) When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecule becomes

1. A) hydrolyzed. B) hydrogenated. C) oxidized. D) reduced. E) an oxidizing agent.

C) oxidized

5) When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a proton), the molecule becomes

A) dehydrogenated. B) oxidized. C) reduced. D) redoxed. E) hydrolyzed.

C) reduced

6) Where does glycolysis take place in eukaryotic cells?

1. A) mitochondrial matrix B) mitochondrial outer membrane C) mitochondrial inner membrane

D) mitochondrial intermembrane space E) cytosol

1. E) cytosol

7) The ATP made during glycolysis is generated by

1. A) substrate-level phosphorylation . B) electron transport. C) photophosphorylation.

D) chemiosmosis. E) oxidation of NADH to NAD+.

A) substrate-level phosphorylation .

8) The oxygen consumed during cellular respiration is involved directly in which process or event?

A) glycolysis B) accepting electrons at the end of the electron transport chain C) the citric acid cycle D) the oxidation of pyruvate to acetyl CoA E) the phosphorylation of ADP to form ATP

B) accepting electrons at the end of the electron transport chain

9) Which process in eukaryotic cells will proceed normally whether oxygen (O2) is present or absent?

A) electron transport B) glycolysis C) the citric acid cycle D) oxidative phosphorylation E) chemiosmosis

C) the citric acid cycle

10) Why are carbohydrates and fats considered high energy foods?

A) They have a lot of oxygen atoms. B) They have no nitrogen in their makeup. C) They can have very long carbon skeletons. D) They have a lot of electrons associated with hydrogen. E) They are easily reduced.

D) They have a lot of electrons associated with hydrogen.

11) During glycolysis, when each molecule of glucose is catabolized to two molecules of pyruvate, most of the potential energy contained in glucose is

A) transferred to ADP, forming ATP. B) transferred directly to ATP. C) retained in the two pyruvates. D) stored in the NADH produced. E) used to phosphorylate fructose to form fructose 6-phosphate.

C) retained in the two pyruvates.

12) In addition to ATP, what are the end products of glycolysis?

A) CO2 and H2O B) CO2 and pyruvate C) NADH and pyruvate D) CO2 and NADH E) H2O, FADH2, and citrate

C) NADH and pyruvate

13) In glycolysis, for each molecule of glucose oxidized to pyruvate

A) two molecules of ATP are used and two molecules of ATP are produced. B) two molecules of ATP are used and four molecules of ATP are produced. C) four molecules of ATP are used and two molecules of ATP are produced. D) two molecules of ATP are used and six molecules of ATP are produced. E) six molecules of ATP are used and six molecules of ATP are produced.

B) two molecules of ATP are used and four molecules of ATP are produced.

14) A molecule that is phosphorylated

1. A) has been reduced as a result of a redox reaction involving the loss of an inorganic phosphate.
2. B) has a decreased chemical reactivity; it is less likely to provide energy for cellular work.
3. C) has been oxidized as a result of a redox reaction involving the gain of an inorganic phosphate.
4. D) has an increased chemical potential energy; it is primed to do cellular work.

E) has less energy than before its phosphorylation and therefore less energy for cellular work.

1. D) has an increased chemical potential energy; it is primed to do cellular work.

15) Which kind of metabolic poison would most directly interfere with glycolysis?

A) an agent that reacts with oxygen and depletes its concentration in the cell B) an agent that binds to pyruvate and inactivates it C) an agent that closely mimics the structure of glucose but is not metabolized D) an agent that reacts with NADH and oxidizes it to NAD+ E) an agent that

C) an agent that closely mimics the structure of glucose but is not metabolized

16) Why is glycolysis described as having an investment phase and a payoff phase?

A) It both splits molecules and assembles molecules. B) It attaches and detaches phosphate groups. C) It uses glucose and generates pyruvate. D) It shifts molecules from cytosol to mitochondrion. E) It uses stored ATP and then forms a net increase in ATP .

1. E) It uses stored ATP and then forms a net increase in ATP .

17) The transport of pyruvate into mitochondria depends on the proton-motive force across the inner mitochondrial membrane. How does pyruvate enter the mitochondrion?

A) active transport B) diffusion C) facilitated diffusion D) through a channel E) through a pore

A) active transport

18) Which of the following intermediary metabolites enters the citric acid cycle and is formed, in part, by the removal of a carbon (CO2) from one molecule of pyruvate?

A) lactate B) glyceraldehydes-3-phosphate C) oxaloacetate D) acetyl CoA E) citrate

D) acetyl CoA

19) During cellular respiration, acetyl CoA accumulates in which location?

A) cytosol B) mitochondrial outer membrane C) mitochondrial inner membrane D) mitochondrial intermembrane space E) mitochondrial matrix

1. E) mitochondrial matrix

20) How many carbon atoms are fed into the citric acid cycle as a result of the oxidation of one molecule of pyruvate?

A) two B) four C) six D) eight E) ten

A) two

21) Carbon dioxide (CO2) is released during which of the following stages of cellular respiration?

1. A) glycolysis and the oxidation of pyruvate to acetyl CoA B) oxidation of pyruvate to acetyl CoA and the citric acid cycle C) the citric acid cycle and oxidative phosphorylation
2. D) oxidative phosphorylation and fermentation E) fermentation and glycolysis

B) oxidation of pyruvate to acetyl CoA and the citric acid cycle

22) A young animal has never had much energy. He is brought to a veterinarian for help and is sent to the animal hospital for some tests. There they discover his mitochondria can use only fatty acids and amino acids for respiration, and his cells produce more lactate than normal. Of the following, which is the best explanation of his condition?

A) His mitochondria lack the transport protein that moves pyruvate across the outer mitochondrial membrane. B) His cells cannot move NADH from glycolysis into the mitochondria. C) His cells contain something that inhibits oxygen use in his mitochondria. D) His cells lack the enzyme in glycolysis that forms pyruvate. E) His cells have a defective electron transport chain, so glucose goes to lactate instead of to acetyl CoA.

A) His mitochondria lack the transport protein that moves pyruvate across the outer mitochondrial membrane.

23) Where are the proteins of the electron transport chain located?

A) cytosol B) mitochondrial outer membrane C) mitochondrial inner membrane D) mitochondrial intermembrane space E) mitochondrial matrix

C) mitochondrial inner membrane

24) In cellular respiration, the energy for most ATP synthesis is supplied by

1. A) high energy phosphate bonds in organic molecules. B) a proton gradient across a membrane.
2. C) converting oxygen to ATP. D) transferring electrons from organic molecules to pyruvate.
3. E) generating carbon dioxide and oxygen in the electron transport chain.

B) a proton gradient across a membrane.

25) During aerobic respiration, which of the following directly donates electrons to the electron transport chain at the lowest energy level?

A) NAD+ B) NADH C) ATP D) ADP + I E) FADH2

E) FADH2

26) The primary role of oxygen in cellular respiration is to

1. A) yield energy in the form of ATP as it is passed down the respiratory chain. B) act as an acceptor for electrons and hydrogen, forming water . C) combine with carbon, forming CO2.

D) combine with lactate, forming pyruvate. E) catalyze the reactions of glycolysis.

B) act as an acceptor for electrons and hydrogen, forming water .

27) Inside an active mitochondrion, most electrons follow which pathway?

A) glycolysis → NADH → oxidative phosphorylation → ATP → oxygen B) citric acid cycle → FADH2 → electron transport chain → ATP C) electron transport chain → citric acid cycle → ATP → oxygen D) pyruvate → citric acid cycle → ATP → NADH → oxygen E) citric acid cycle → NADH → electron transport chain → oxygen

1. E) citric acid cycle → NADH → electron transport chain → oxygen

28) In chemiosmotic phosphorylation, what is the most direct source of energy that is used to convert ADP + i to ATP?

1. A) energy released as electrons flow through the electron transport system B) energy released from substrate-level phosphorylation C) energy released from movement of protons through ATP synthase, against the electrochemical gradien t D) energy released from movement of protons through ATP synthase, down the electrochemical gradient E) No external source of energy is required because the reaction is exergonic.

D) energy released from movement of protons through ATP synthase, down the electrochemical gradient

29) Energy released by the electron transport chain is used to pump H+ into which location in eukaryotic cells?

A) cytosol B) mitochondrial outer membrane C) mitochondrial inner membrane D) mitochondrial intermembrane space E) mitochondrial matrix

B) mitochondrial outer membrane

30) The direct energy source that drives ATP synthesis during respiratory oxidative phosphorylation in eukaryotic cells is

A) oxidation of glucose to CO2 and water. B) the thermodynamically favorable flow of electrons from NADH to the mitochondrial electron transport carriers. C) the final transfer of electrons to oxygen. D) the proton-motive force across the inner mitochondrial membrane. E) the thermodynamically favorable transfer of phosphate from glycolysis and the citric acid cycle intermediate molecules of ADP.

D) the proton-motive force across the inner mitochondrial membrane.

31) When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is the

A) formation of ATP. B) reduction of NAD+. C) restoration of the Na+/K+ balance across the membrane. D) creation of a proton-motive force. E) lowering of pH in the mitochondrial matrix.

D) creation of a proton-motive force.

32) Where is ATP synthase located in the mitochondrion?

A) cytosol B) electron transport chain C) outer membrane D) inner membrane E) mitochondrial matrix

D) inner membrane

33) Approximately how many molecules of ATP are produced from the complete oxidation of two molecules of glucose (C6H12O6) in aerobic cellular respiration?

A) 2 B) 4 C) 15 D) 30-32 E) 60-64

C) 15

34) What is proton-motive force?

A) the force required to remove an electron from hydrogen B) the force exerted on a proton by a transmembrane proton concentration gradient C) the force that moves hydrogen into the intermembrane space D) the force that moves hydrogen into the mitochondrion E) the force that moves hydrogen to NAD+

B) the force exerted on a proton by a transmembrane proton concentration gradient

35) In liver cells, the inner mitochondrial membranes are about five times the area of the outer mitochondrial membranes. What purpose must this serve?

A) It allows for an increased rate of glycolysis. B) It allows for an increased rate of the citric acid cycle. C) It increases the surface for oxidative phosphorylation. D) It increases the surface for substrate-level phosphorylation. E) It allows the liver cell to have fewer mitochondria.

C) It increases the surface for oxidative phosphorylation.

36) In prokaryotes, the respiratory electron transport chain is located

A) in the mitochondrial inner membrane. B) in the mitochondrial outer membrane. C) in the plasma membrane. D) in the cytoplasm. E) in the bacterial outer membrane.

C) in the plasma membrane.

37) Which of the following normally occurs regardless of whether or not oxygen (O2) is present?

A) glycolysis B) fermentation C) oxidation of pyruvate to acetyl CoA D) citric acid cycle E) oxidative phosphorylation (chemiosmosis)

A) glycolysis

38) Which of the following occurs in the cytosol of a eukaryotic cell?

A) glycolysis and fermentation B) fermentation and chemiosmosis C) oxidation of pyruvate to acetyl CoA D) citric acid cycle E) oxidative phosphorylation

A) glycolysis and fermentation

39) The ATP made during fermentation is generated by which of the following?

A) the electron transport chain B) substrate-level phosphorylation C) chemiosmosis D) oxidative phosphorylation E) aerobic respiration

B) substrate-level phosphorylation

40) In the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of

A) ATP, CO2, and ethanol (ethyl alcohol). B) ATP, CO2, and lactate. C) ATP, NADH, and pyruvate. D) ATP, pyruvate, and oxygen. E) ATP, pyruvate, and acetyl CoA.

A) ATP, CO2, and ethanol (ethyl alcohol).

41) In alcohol fermentation, NAD+ is regenerated from NADH by

1. A) reduction of acetaldehyde to ethanol (ethyl alcohol). B) oxidation of pyruvate to acetyl CoA.

C) reduction of pyruvate to form lactate. D) oxidation of ethanol to acetyl CoA. E) reduction of ethanol to pyruvate.

A) reduction of acetaldehyde to ethanol (ethyl alcohol).

42) Phosphofructokinase is an allosteric enzyme that catalyzes the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate, an early step of glycolysis. In the presence of oxygen, an increase in the amount of ATP in a cell would be expected to

A) inhibit the enzyme and thus slow the rates of glycolysis and the citric acid cycle. B) activate the enzyme and thus slow the rates of glycolysis and the citric acid cycle. C) inhibit the enzyme and thus increase the rates of glycolysis and the citric acid cycle. D) activate the enzyme and increase the rates of glycolysis and the citric acid cycle. E) inhibit the enzyme and thus increase the rate of glycolysis and the concentration of citrate.

1. E) inhibit the enzyme and thus increase the rate of glycolysis and the concentration of citrate.

43) During intense exercise, as skeletal muscle cells go into anaerobiosis, the human body will increase its catabolism of

A) fats only. B) carbohydrates only. C) proteins only. D) fats, carbohydrates, and proteins. E) fats and proteins only.

B) carbohydrates only.