Bio CH 13,14,15

Question 1

When comparing the controlled, stepwise oxidation of sugar in cells with burning of the same fuel molecule in nonliving conditions, the free energy released by the complete oxidative breakdown of glucose to CO2 and H2O is
Question 1 Answer

a.
much lower.

b.
much higher.

c.
about the same.

d.
impossible to measure.

Answer 1

about the same.

Question 2

Steps 7 and 10 of glycolysis result in substrate-level phosphorylation. Which of the following best describes this process?
Question 2 Answer

a.
ATP is being hydrolyzed to phosphorylate the substrate.

b.
The energy derived from substrate oxidation is coupled to the conversion of ADP to ATP.

c.
Two successive phosphates are transferred, first to AMP and then to ADP, finally forming ATP.

d.
The substrate is hydrolyzed using ATP as an energy source.
Feedback
The

Answer 2

The energy derived from substrate oxidation is coupled to the conversion of ADP to ATP.

Question 3

The advantage to the cell of the gradual oxidation of glucose during cellular respiration compared with its combustion to CO2 and H2O in a single step is that
Question 3 Answer

a.
more free energy is released for a given amount of glucose oxidized.

b.
no energy is lost as heat.

c.
energy can be extracted in usable amounts.

d.
more CO2 is produced for a given amount of glucose oxidized.

Answer 3

energy can be extracted in usable amounts

Question 4

The primary reason that oxygen is required for the citric acid cycle to continue is that
Question 4 Answer

a.
NAD+ must be regenerated to keep the citric acid cycle going, and that requires the oxygen-dependent electron transport chain.

b.
oxygen is required for the oxidizing steps in the citric acid cycle.

c.
without oxygen, production of pyruvate from glucose will soon cease and that will lead to a shutdown of the citric acid cycle.

d.
oxygen is directly required to produce carbon dioxide in the citric acid cycle.

Answer 4

NAD+ must be regenerated to keep the citric acid cycle going, and that requires the oxygen-dependent electron transport chain.

Question 5

A dehydrogenase is an enzyme that catalyzes
Question 5 Answer

a.
the rearrangement of bonds within a single molecule.

b.
a change in the position of a specific chemical group within a single molecule.

c.
the oxidation of a molecule by removing a hydride ion.

d.
the addition of phosphate groups to other molecules.

Answer 5

the oxidation of a molecule by removing a hydride ion.

Question 6

In step 4 of the citric acid cycle, the reduction of NAD+ to NADH is coupled to the generation of CO2 and the formation of a high-energy thioester bond. The energy of the thioester bond is harnessed in step 5. The energy is used to generate a
Question 6 Answer

a.
molecule of GTP.

b.
molecule of ATP.

c.
proton gradient.

d.
molecule of NADH.

Answer 6

molecule of GTP.

Question 7

The conversion of fructose 1,6-bisphosphate to fructose 6-phosphate is catalyzed by a fructose 1,6-bisphosphatase and is one of the final steps in gluconeogenesis. Which of the following molecules is an allosteric activator of this enzyme?
Question 7 Answer

a.
Pi

b.
AMP

c.
ADP

d.
ATP

Answer 7

ATP

Question 8

In the final step of the citric acid cycle, oxaloacetate is regenerated through the oxidation of malate. This is coupled with the production of which other molecule?
Question 8 Answer

a.
FADH

b.
NADH

c.
GTP

d.
CO2

Answer 8

NADH

Question 9

Which of the following cells rely exclusively on glycolysis to supply them with ATP?
Question 9 Answer

a.
anaerobically growing yeast

b.
aerobic bacteria

c.
skeletal muscle cells

d.
plant cells

Answer 9

anaerobically growing yeast

Question 10

Glyceraldehyde 3-phosphate dehydrogenase operates by stripping a hydride ion from its substrate. Which molecule is the recipient of the proton and two electrons during this transfer?
Question 10 Answer

a.
oxygen

b.
acetyl CoA

c.
NAD+

d.
FADH

Answer 10

NAD+

Question 11

In humans, glycogen is a more useful food-storage molecule than fat because
Question 11 Answer

a.
a gram of glycogen produces more energy than a gram of fat.

b.
it can be utilized to produce ATP under anaerobic conditions, whereas fat cannot.

c.
it binds water and is therefore useful in keeping the body hydrated.

d.
for the same amount of energy storage, glycogen occupies less space in a cell than does fat.

Answer 11

it can be utilized to produce ATP under anaerobic conditions, whereas fat cannot.

Question 12

Pyruvate can be converted into many other molecules by various biosynthetic and metabolic pathways, which makes it a central hub in the regulation of cellular metabolism. Which of the following molecules is NOT made from pyruvate?
Question 12 Answer

a.
oxaloacetate

b.
ethanol

c.
lactate

d.
NADH

Answer 12

NADH

Question 13

The first energy-generating steps in glycolysis begin when glyceraldehyde 3-phosphate undergoes an energetically favorable reaction in which it is simultaneously oxidized and phosphorylated by the enzyme glyceraldehyde 3-phosphate dehydrogenase to form 1,3-bisphosphoglycerate, with the accompanying conversion of NAD+ to NADH. In a second energetically favorable reaction catalyzed by a second enzyme, the 1,3-bisphosphoglycerate is then converted to 3-phosphoglycerate, with the accompanying conversion of ADP to ATP. Which of the following statements is true about this reaction?
Question 13 Answer

a.
The reaction glyceraldehyde 3-phosphate → 1,3-bisphosphoglycerate should be inhibited when levels of NADH fall.

b.
The ΔG° for the oxidation of the aldehyde group on glyceraldehyde 3-phosphate to form a carboxylic acid is more negative than the ΔG° for ATP hydrolysis.

c.
The energy stored in the phosphate bond of glyceraldehyde 3-phosphate contributes to driving the reaction forward.

d.
The cysteine side chain on the enzyme is oxidized by NAD+.

Answer 13

The ΔG° for the oxidation of the aldehyde group on glyceraldehyde 3-phosphate to form a carboxylic acid is more negative than the ΔG° for ATP hydrolysis.

Question 14

The conversion of glyceraldehyde 3-phosphate to 1,3 bisphosphoglycerate in step 6 of glycolysis generates a “high-energy” phosphoanhydride bond. Which of the following best describes what happens to that bond in step 7?
Question 14 Answer

a.
It is hydrolyzed to drive the formation of ATP.

b.
It is hydrolyzed to drive the formation of NADH.

c.
It is hydrolyzed to generate pyruvate.

d.
It is oxidized to CO2.

Answer 14

It is hydrolyzed to drive the formation of ATP.

Question 15

Step 3 in glycolysis requires the activity of phosphofructokinase to convert fructose 6-phosphate into fructose 1,6-bisphosphate. Which of the following molecules is an allosteric inhibitor of this enzyme?
Question 15 Answer

a.
Pi

b.
AMP

c.
ADP

d.
ATP

Answer 15

ATP

Question 16

Select the best option to fill in the blanks: Fermentation is a(n) __________ process that converts __________ into carbon dioxide and __________.
Question 16 Answer

a.
anaerobic; pyruvate; ethanol

b.
anaerobic; lactate; ethanol

c.
eukaryotic; glyceraldehyde 3-phosphate; ethanol

d.
prokaryotic; lactate; propanol

Answer 16

anaerobic; pyruvate; ethanol

Question 17

What purpose does the phosphorylation of glucose to glucose 6-phosphate by the enzyme hexokinase serve as the first step in glycolysis?
Question 17 Answer

a.
It helps drive the uptake of glucose from outside the cell.

b.
It generates a high-energy phosphate bond.

c.
It converts ATP to a more useful form.

d.
It enables the glucose 6-phosphate to be recognized by phosphofructokinase, the next enzyme in the glycolytic pathway.

Answer 17

It helps drive the uptake of glucose from outside the cell.

Question 18

Foods are broken down into simple molecular subunits for distribution and use throughout the body. Which type of simple subunits, listed below, is used preferentially as an energy source?
Question 18 Answer

a.
simple sugars

b.
proteins

c.
free fatty acids

d.
glycerol

Answer 18

simple sugars

Question 19

Which of the following steps or processes in aerobic cell respiration includes the production of carbon dioxide?
Question 19 Answer

a.
breakdown of glycogen

b.
glycolysis

c.
conversion of pyruvate to acetyl CoA

d.
oxidative phosphorylation
Feedback

Answer 19

conversion of pyruvate to acetyl CoA

Question 20

Despite its very different structure, FADH2, like NADH, is a carrier of
Question 20 Answer

a.
phosphate.

b.
heat.

c.
oxygen atoms and high-energy glucose.

d.
hydrogen atoms and high-energy electrons.

Answer 20

hydrogen atoms and high-energy electrons.

Question 21

Glycolysis is an anaerobic process used to catabolize glucose. What does it mean for this process to be anaerobic?
Question 21 Answer

a.
No oxygen is required.

b.
No oxidation occurs.

c.
It takes place in the lysosome.

d.
Glucose is broken down by the addition of electrons.

Answer 21

No oxygen is required

Question 22

The final metabolite produced by glycolysis is
Question 22 Answer

a.
acetyl CoA.

b.
pyruvate.

c.
3-phosphoglycerate.

d.
glyceraldehyde 3-phosphate.

Answer 22

Pyruvate

Question 23

Fatty acids can easily be used to generate energy for the cell. Which of the following fatty acids will yield more energy?
Question 23 Answer

a.
CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH = CH-COOH

b.
CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-COOH

c.
CH3-CH = CH-CH2-CH2-CH2-CH2-CH = CH-COOH

d.
CH3-CH2-CH2-CH2-CH2-CH2-CH2-COOH

Answer 23

CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-COOH

Question 24

The citric acid cycle is a critical sequence of reactions for energy production, which take place in the matrix of the mitochondria. The reaction cycle requires materials from the cytosol to be converted into acetyl CoA, which represents the starting point of a new cycle. Which of the following statements about acetyl CoA is true?
Question 24 Answer

a.
Amino acids can be converted into acetyl CoA.

b.
Pyruvate is converted into acetyl CoA in the cytosol.

c.
Triacylglycerol molecules are transported into the mitochondrial matrix and cleaved by lipases to produce acetyl CoA.

d.
Oxaloacetate is converted directly into acetyl CoA to feed the citric acid cycle.

Answer 24

Amino acids can be converted into acetyl CoA.

Question 25

On a diet consisting of nothing but protein, which of the following is the most likely outcome? Question 25 Answer a. loss of weight because amino acids cannot be used for the synthesis of fat b. muscle gain because the amino acids will go directly into building muscle c. tiredness because amino acids cannot be used to generate energy d. excretion of more nitrogenous (ammonia-derived) wastes than with a more balanced diet

Answer 25

excretion of more nitrogenous (ammonia-derived) wastes than with a more balanced diet

Question 26

Which of the following processes does NOT take place in the mitochondria? Question 26 Answer a. citric acid cycle b. conversion of pyruvate to activated acetyl groups c. oxidation of fatty acids to acetyl CoA d. glycogen breakdown

Answer 26

glycogen breakdown

Question 27

Which of the following polymers of glucose is used as a vehicle to store energy reserves in animal cells? Question 27 Answer a. glucagon b. glycogen c. starch d. glycerol

Answer 27

Glycogen

Question 28

The concentration of H+ ions inside the mitochondrial matrix is lower than it is in the cytosol or the mitochondrial intermembrane space. What would be the immediate effect of a membrane-permeable compound that carries and releases protons into the mitochondrial matrix? Question 28 Answer a. inhibition of the electron-transport chain b. inhibition of ATP synthesis c. increased import of ADP into the matrix d. inhibition of the citric acid cycle

Answer 28

inhibition of ATP synthesis

Question 29

The citric acid cycle is a series of oxidation reactions that removes carbon atoms from substrates in the form of CO2. Where do the oxygen atoms in the carbon dioxide molecules come from? Question 29 Answer a. water b. phosphates c. molecular oxygen d. acetyl CoA

Answer 29

Water

Question 30

In the absence of oxygen, yeast cells can switch to a completely anaerobic metabolism called fermentation. Which of the following is a final product of fermentation in yeast? Figure 13-2 Question 30 Answer a. Figure a b. Figure b c. Figure c d. Figure d

Answer 30

Figure b

Question 31

A kinase is an enzyme that catalyzes Question 31 Answer a. the rearrangement of bonds within a single molecule. b. a change in the position of a specific chemical group within a single molecule. c. the oxidation of a molecule by removing a hydride ion. d. the addition of phosphate groups to other molecules.

Answer 31

the addition of phosphate groups to other molecules.

Question 32

In anaerobic conditions, skeletal muscle produces Question 32 Answer a. lactate and CO2. b. ethanol and CO2. c. lactate only. d. ethanol only.

Answer 32

lactate only.

Question 33

Which reaction does the enzyme phosphoglucose isomerase catalyze? Question 33 Answer a. glucose → glucose 6-phosphate b. fructose 6-phosphate → fructose 1,6-bisphosphate c. glucose 6-phosphate → fructose 6-phosphate d. glucose → glucose 1-phosphate

Answer 33

glucose 6-phosphate → fructose 6-phosphate

Question 34

In aerobic bacteria, where do glycolysis, acetyl CoA production, and the citric acid cycle take place, respectively? Question 34 Answer a. Glycolysis takes place in the cytosol, acetyl CoA production and citric acid cycle in the mitochondrion. b. All take place in the bacterial cytosol. c. Of the three, only glycolysis occurs in aerobic bacteria, and it takes place in the cytoplasm. d. Glycolysis takes place in the intermembrane space, acetyl CoA production and citric acid cycle in the matrix.

Answer 34

All take place in the bacterial cytosol.

Question 35

A mutase is an enzyme that catalyzes Question 35 Answer a. the rearrangement of bonds within a single molecule. b. a change in the position of a specific chemical group within a single molecule. c. the oxidation of a molecule by removing a hydride ion. d. the addition of phosphate groups to other molecules.

Answer 35

a change in the position of a specific chemical group within a single molecule.

Question 36

When glucose is being used up and not replaced from food intake, the blood sugar level can be maintained by synthesizing glucose from smaller molecules such as pyruvate or lactate. This process is called gluconeogenesis. Which organ is principally responsible for supplying glucose to the rest of the body when glucose reserves are low? Question 36 Answer a. liver b. pancreas c. spleen d. gallbladder

Answer 36

Liver

Question 37

In step 4 of glycolysis, a six-carbon sugar (fructose 1,6-bisphosphate) is cleaved to produce two three-carbon molecules (dihydroxyacetone phosphate and glyceraldehyde 3-phosphate). Which enzyme catalyzes this reaction? Question 37 Answer a. aldolase b. phosphoglucose isomerase c. enolase d. triose phosphate isomerase

Answer 37

aldolase

Question 38

Glycolysis generates more stored energy than it expends. What is the net number of activated carrier molecules produced in this process from one molecule of glucose (number and type of molecules produced minus the number of those molecules used as input)? Question 38 Answer a. 6 ATP, 2 NADH b. 4 ATP, 4 NADH c. 2 ATP, 2 NADH d. 4 ATP, 2 NADH

Answer 38

2 ATP, 2 NADH

Question 39

In the final stage of the oxidation of food molecules, a gradient of protons is formed across the inner mitochondrial membrane, which is normally impermeable to protons. If cells were exposed to an agent that causes the membrane to become freely permeable to protons, which of the following effects would you expect to observe? Question 39 Answer a. The ratio of ATP to ADP in the cytoplasm would fall. b. NADH would build up. c. Carbon dioxide production would cease. d. The consumption of oxygen would fall.

Answer 39

The ratio of ATP to ADP in the cytoplasm would fall.

Question 40

If a cell in anaerobic conditions were unable to ferment and therefore unable to convert pyruvate to lactate or ethanol, which of the following best explains why simply discarding pyruvate as a waste product is not an option? Question 40 Answer a. Lactate and ethanol are critical alternative energy sources when oxygen is absent. b. Pyruvate cannot be transported across cellular membranes. c. Without pyruvate present, additional glucose cannot be imported into cells. d. NAD+ would not be regenerated from NADH.

Answer 40

NAD+ would not be regenerated from NADH

Question 41

What is the function of the heme groups in the complexes of the electron transport chain? Question 1 Answer a. to reduce NADH and FADH2 b. to transport protons across the inner membrane c. to bind other intermembrane proteins and release heat energy as the electrons pass through the inner membrane d. to provide a pathway for electrons to flow through the complex to reaction centers of higher redox potentials

Answer 41

to provide a pathway for electrons to flow through the complex to reaction centers of higher redox potentials

Question 42

Below is a picture of a mitochondrion located in a cell. The letter A represents what region? Question 2 Answer a. nucleoplasm b. rough endoplasmic reticulum c. cytoplasm d. extracellular space

Answer 42

cytoplasm

Question 43

If you shine light on chloroplasts and measure the rate of photosynthesis as a function of light intensity, you get a curve that reaches a plateau at a fixed rate of photosynthesis, x, as shown in the figure below. Which of the following conditions will increase the value of x? Question 3 Answer a. increasing the number of chlorophyll molecules in the antenna complexes b. increasing the number of reaction centers c. adding a powerful oxidizing agent d. decreasing the wavelength of light used

Answer 43

increasing the number of reaction centers

Question 44

The photosystems in chloroplasts contain hundreds of chlorophyll molecules, most of which are part of Question 4 Answer a. plastoquinone. b. the antenna complex. c. the reaction center. d. the ferredoxin complex.

Answer 44

the antenna complex.

Question 45

Which of the following statements is true? Question 5 Answer a. The NADH dehydrogenase complex does not pump protons across the membrane. b. The pH in the mitochondrial matrix is higher than the pH in the intermembrane space. c. The proton concentration gradient and the membrane potential across the inner mitochondrial membrane tend to work against each other in driving protons from the intermembrane space into the matrix. d. The difference in proton concentration across the inner mitochondrial membrane has a much larger effect than the membrane potential on the total proton-motive force.

Answer 45

The pH in the mitochondrial matrix is higher than the pH in the intermembrane space.

Question 46

Which of the following is NOT part of the process known as “oxidative phosphorylation”? Question 6 Answer a. Molecular oxygen serves as a final electron acceptor. b. FADH2 and NADH become oxidized as they transfer a pair of electrons to the electron-transport chain. c. The electron carriers in the electron-transport chain toggle between reduced and oxidized states as electrons are passed along. d. ATP molecules are produced in the cytosol as glucose is converted into pyruvate.

Answer 46

ATP molecules are produced in the cytosol as glucose is converted into pyruvate.

Question 47

Which of the following statements about “redox potential” is true? Question 7 Answer a. Redox potential is a measure of a molecule’s capacity to strip electrons from oxygen. b. For molecules that have a strong tendency to pass along their electrons, the standard redox potential is negative. c. The transfer of electrons from cytochrome c oxidase to oxygen has a negative redox potential. d. A molecule’s redox potential is a measure of the molecule’s capacity to pass along electrons to oxygen.

Answer 47

For molecules that have a strong tendency to pass along their electrons, the standard redox potential is negative

Question 48

Stage 2 of photosynthesis, sometimes referred to as the dark reactions, involves the reduction of CO2 to produce organic compounds such as sucrose. What cofactor is the electron donor for carbon fixation? Question 8 Answer a. H2O b. NADH c. FADH2 d. NADPH

Answer 48

NADPH

Question 49

NADH and FADH2 carry high-energy electrons that are used to power the production of ATP in the mitochondria. These cofactors are generated during glycolysis, the citric acid cycle, and the fatty acid oxidation cycle. Which molecule, and from which biochemical pathway stated below, can produce the most ATP? Question 9 Answer a. NADH from glycolysis b. FADH2 from the fatty acid cycle c. NADH from the citric acid cycle d. FADH2 from the citric acid cycle

Answer 49

NADH from the citric acid cycle

Question 50

Osmosis describes the movement of water across a biological membrane and down its concentration gradient. In chemiosmosis, useful energy is harnessed by the cell from the movement of __________ across the inner mitochondrial membrane into the matrix __________ a concentration gradient. Question 10 Answer a. ATP; against b. protons; down c. electrons; down d. ADP; against

Answer 50

protons; down

Question 51

Which of the following statements describes the phosphorylation event that occurs during the process known as “oxidative phosphorylation”? Question 11 Answer a. A phosphate group is added to ADP. b. ATP is hydrolyzed in order to add phosphate groups to protein substrates. c. A phosphate group is added to molecular oxygen. d. A phosphate group is transported into the mitochondrial matrix, increasing the local phosphate concentration.

Answer 51

A phosphate group is added to ADP

Question 52

What is the result of the electron transfers in stage 1 of the membrane-based processes that drive ATP synthesis in mitochondria? Question 12 Answer a. OH- is oxidized to O2. b. Pyruvate is oxidized to CO2. c. O2 is reduced to H2O. d. H- is converted to H2.

Answer 52

O2 is reduced to H2O

Question 53

In stage 1 of photosynthesis, a proton gradient is generated and ATP is synthesized. Where do protons become concentrated in the chloroplast? Question 13 Answer a. thylakoid space b. stroma c. inner membrane d. thylakoid membrane

Answer 53

thylakoid space

Question 54

Photosynthesis is a process that takes place in chloroplasts and uses light energy to generate high-energy electrons, which are passed along an electron-transport chain. Where are the proteins of the electron-transport chain located in chloroplasts? Question 14 Answer a. thylakoid space b. stroma c. inner membrane d. thylakoid membrane

Answer 54

thylakoid membrane

Question 55

Which two regions or spaces have nearly identical pH levels and, therefore, no proton motive force? Question 15 Answer a. C and D b. B and C c. A and B d. A and C

Answer 55

A and B

Question 56

Modern eukaryotes depend on mitochondria to generate most of the cell’s ATP. What is the approximate number of ATP molecules that can be generated from a single molecule of glucose? Question 16 Answer a. 30 b. 2 c. 20 d. 40

Answer 56

30

Question 57

Which component of the electron-transport chain is required to combine the pair of electrons with molecular oxygen? Question 17 Answer a. cytochrome c b. cytochrome b-c1 complex c. ubiquinone d. cytochrome c oxidase

Answer 57

cytochrome c oxidase

Question 58

What does it mean that electrons are high energy? Compare NADH or complex I of the electron transport chain to low energy electrons in complex IV or H2O. Question 18 Answer a. Low-energy electrons are in a stable noncovalent bond, such as the bonds in water. b. Electrons that are prevented from joining the valence electrons in certain atoms, such as carbon in NADH and complex I, give the electrons a high energy status. c. In the presence of oxygen, the electrons are likely to transform into neutrons due to the electronegativity of oxygen. d. High-energy electrons are not in the most stable polar covalent bond and can thus be attracted to other elements with a higher redox potential or higher electronegativity value, like oxygen.

Answer 58

High-energy electrons are not in the most stable polar covalent bond and can thus be attracted to other elements with a higher redox potential or higher electronegativity value, like oxygen.

Question 59

Which mitochondrial space or region has the lowest H+ concentration? Question 19 Answer a. A b. B c. C d. D

Answer 59

C

Question 60

In the electron-transport chain in chloroplasts, __________-energy electrons are taken from __________. Question 20 Answer a. high; H2O b. low; H2O c. high; NADPH d. low; NADPH

Answer 60

low; H2O

Question 61

Experimental evidence supporting the chemiosmotic hypothesis was gathered by using artificial vesicles containing a protein that can pump protons in one direction across the vesicle membrane to create a proton gradient. Which protein was used to generate the gradient in a highly controlled manner? Question 21 Answer a. cytochrome c oxidase b. NADH dehydrogenase c. cytochrome c d. bacteriorhodopsin

Answer 61

bacteriorhodopsin

Question 62

The letter that best represents where the Fo region of ATP synthase is located is C, the matrix. Question 22 Answer a. True b. False

Answer 62

False

Question 63

The overall relationship that links high-energy bond-forming reactions to proton transport processes in the mitochondria is called Question 23 Answer a. chemiosmotic coupling. b. proton pumping. c. electron transfer. d. ATP synthesis.

Answer 63

chemiosmotic coupling.

Question 64

During stage 2 of oxidative phosphorylation, ATP synthesis is powered by movement of __________ ions through the __________. Question 24 Answer a. H+; H+ pump b. OH-; porin complex c. H+; ATP synthase d. elections; electron-transport chain

Answer 64

H+; ATP synthase

Question 65

Which of the following components of the electron-transport chain does NOT act as a proton pump? Question 25 Answer a. NADH dehydrogenase b. cytochrome c c. cytochrome c reductase d. cytochrome c oxidase

Answer 65

cytochrome c

Question 66

NADH contains a high-energy bond that, when cleaved, donates a pair of electrons to the electron-transport chain. What are the immediate products of this bond cleavage? Question 26 Answer a. NAD+ + OH- b. NAD+ + H- c. NAD- + H+ d. NAD + H

Answer 66

NAD+ + H-

Question 67

What is the source of protons that are pumped out of the mitochondrial matrix in stage 1 of oxidative phosphorylation? Question 27 Answer a. NADH b. H2O c. FADH d. H2S

Answer 67

H2O

Question 68

Which of the following statements about mitochondrial division is true? Question 28 Answer a. Mitochondria divide in synchrony with the cell. b. The rate of mitochondrial division is the same in all cell types. c. Mitochondrial division is mechanistically like prokaryotic cell division. d. Mitochondria cannot divide and produce energy for the cell at the same time.

Answer 68

Mitochondrial division is mechanistically like prokaryotic cell division.

Question 69

The generation of ATP from the proton gradient is a wonderful application of the first law of thermodynamics. What forms of energy are used to generate ATP during oxidative phosphorylation in mitochondria? Question 29 Answer a. potential energy to vibrational (heat) energy to chemical bond energy in ATP b. mechanical energy of the proton pumping to proton motive force to mechanical energy of ATP synthase to chemical bond energy in ATP c. heat energy to mechanical energy of proton pumps to proton motive force to chemical bond energy d. chemical bond energy to mechanical energy of ATP synthase to chemical bond energy in ATP

Answer 69

mechanical energy of the proton pumping to proton motive force to mechanical energy of ATP synthase to chemical bond energy in ATP

Question 70

Which of the following statements describes the mitochondrial matrix? Question 30 Answer a. It is permeable to molecules with molecular mass as high as 5000 Daltons. b. It contains transporters for ATP molecules. c. It contains proteins that are released during apoptosis. d. It contains enzymes required for the oxidation of fatty acids.

Answer 70

It contains enzymes required for the oxidation of fatty acids.

Question 71

Which of the following statements about phagocytic cells in animals is FALSE? Question 1 Answer a. Phagocytic cells are important in the gut to take up large particles of food. b. Phagocytic cells scavenge dead and damaged cells and cell debris. c. Phagocytic cells can engulf invading microorganisms and deliver them to their lysosomes for destruction. d. Phagocytic cells extend pseudopods that surround the material to be ingested.

Answer 71

Phagocytic cells are important in the gut to take up large particles of food.

Question 72

You are interested in Fuzzy, a soluble protein that functions within the ER lumen. Given that information, which of the following statements must be true? Question 2 Answer a. Fuzzy has a C-terminal signal sequence that binds to SRP. b. Only one ribosome can be bound to the mRNA encoding Fuzzy during translation. c. Fuzzy must contain a hydrophobic stop-transfer sequence. d. Once the signal sequence from Fuzzy has been cleaved, the signal peptide will be ejected into the ER membrane and degraded.

Answer 72

Once the signal sequence from Fuzzy has been cleaved, the signal peptide will be ejected into the ER membrane and degraded.

Question 73

Which of the following statements about disulfide bond formation is FALSE? Question 3 Answer a. Disulfide bonds do not form under reducing environments. b. Disulfide bonding occurs by the oxidation of pairs of cysteine side chains on the protein. c. Disulfide bonding stabilizes the structure of proteins. d. Disulfide bonds form spontaneously within the ER because the lumen of the ER is oxidizing.

Answer 73

Disulfide bonds form spontaneously within the ER because the lumen of the ER is oxidizing.

Question 74

Which of the following statements is true? Question 4 Answer a. Lysosomes originated from the engulfment of bacteria specialized for digestion. b. The nuclear membrane arose from the plasma membrane invaginating around the DNA. c. Because bacteria do not have mitochondria, they cannot produce ATP in a membrane-dependent fashion. d. Chloroplasts and mitochondria share their DNA.

Answer 74

The nuclear membrane arose from the plasma membrane invaginating around the DNA.

Question 75

Proteins that are fully translated in the cytosol and lack a sorting signal will end up in the Question 5 Answer a. cytosol. b. mitochondria. c. interior of the nucleus. d. nuclear membrane.

Answer 75

cytosol.

Question 76

Which of the following statements about vesicle budding from the Golgi is FALSE? Question 6 Answer a. Clathrin molecules are important for binding to and selecting cargo molecules for transport. b. Adaptins interact with clathrin. c. Once vesicle budding occurs, clathrin molecules are released from the vesicle. d. Clathrin molecules act at the cytosolic surface of the Golgi membrane.

Answer 76

Clathrin molecules are important for binding to and selecting cargo molecules for transport.

Question 77

After isolating the rough endoplasmic reticulum from the rest of the cytoplasm, you purify the RNAs attached to it. Which of the following proteins do you expect the RNA from the rough endoplasmic reticulum to encode? Question 7 Answer a. soluble secreted proteins b. ER membrane proteins c. plasma membrane proteins d. All these answers are correct.

Answer 77

All these answers are correct.

Question 78

Where are chloroplast proteins translated? Question 8 Answer a. in the cytosol b. in the chloroplast c. on the endoplasmic reticulum d. in both the cytosol and the chloroplast

Answer 78

in both the cytosol and the chloroplast

Question 79

Signal sequences that direct proteins to the correct compartment are Question 9 Answer a. added to proteins through post-translational modification. b. added to a protein by a protein translocator. c. encoded in the amino acid sequence and sufficient for targeting a protein to its correct destination. d. always removed once a protein is at the correct destination.

Answer 79

encoded in the amino acid sequence and sufficient for targeting a protein to its correct destination.

Question 80

Your friend has just joined a lab that studies vesicle budding from the Golgi and has been given a cell line that does not form mature vesicles. He wants to start designing some experiments but was not listening carefully when he was told about the molecular defect of this cell line. He is too embarrassed to ask and comes to you for help. He does recall that this cell line forms coated pits, but vesicle budding and the removal of coat proteins don’t happen. Which of the following proteins might be lacking in this cell line? Question 10 Answer a. clathrin b. Rab c. dynamin d. adaptin

Answer 80

Dynamin

Question 81

A cargo molecule is brought into a cell via receptor-mediated endocytosis. Which of the following factors causes the receptor to release its cargo molecule into the lumen of the endosome? Question 11 Answer a. proteolytic digestion of the receptor b. acidic pH c. high salt concentrations d. competitive inhibitors

Answer 81

acidic pH

Question 82

Molecules to be packaged into vesicles for transport are selected by Question 12 Answer a. clathrin. b. adaptins. c. dynamin. d. SNAREs.

Answer 82

Adaptins

Question 83

In which cellular location would you expect to find ribosomes translating mRNAs that encode ribosomal proteins? Question 13 Answer a. the nucleus b. on the rough ER c. in the cytosol d. in the lumen of the ER

Answer 83

in the cytosol

Question 84

Proteins that are fully translated in the cytosol do not end up in Question 14 Answer a. the cytosol. b. the mitochondria. c. the interior of the nucleus. d. transport vesicles.

Answer 84

transport vesicles.

Question 85

Which of the following statements about the endoplasmic reticulum (ER) is FALSE? Question 15 Answer a. The ER is the major site for new membrane synthesis in the cell. b. Proteins to be delivered to the ER lumen are synthesized on the smooth ER. c. Steroid hormones are synthesized on the smooth ER. d. The ER membrane is contiguous with the outer nuclear membrane.

Answer 85

Proteins to be delivered to the ER lumen are synthesized on the smooth ER.

Question 86

Which of the following statements about secretion is true? Question 16 Answer a. The membrane of a secretory vesicle fuses with the plasma membrane when the vesicle discharges its contents to the cell’s exterior. b. Vesicles for regulated exocytosis do not bud off the trans Golgi network until the cell has received the appropriate signal. c. The signal sequences of proteins destined for constitutive exocytosis ensure their packaging into the correct vesicles. d. Proteins destined for constitutive exocytosis aggregate because of the acidic pH of the trans Golgi network.

Answer 86

The membrane of a secretory vesicle fuses with the plasma membrane when the vesicle discharges its contents to the cell’s exterior.

Question 87

Vesicles from the ER enter the Golgi at the Question 17 Answer a. medial cisternae. b. trans Golgi network. c. cis Golgi network. d. trans cisternae.

Answer 87

cis Golgi network.

Question 88

Which of the following statements about the protein quality control system in the ER is FALSE? Question 18 Answer a. Chaperone proteins help misfolded proteins fold properly. b. Proteins that are misfolded are degraded in the ER lumen. c. Protein complexes are checked for proper assembly before they can exit the ER. d. A chaperone protein will bind to a misfolded protein to retain it in the ER.

Answer 88

Proteins that are misfolded are degraded in the ER lumen.

Question 89

Which of the following statements about transport into mitochondria and chloroplasts is FALSE? Question 19 Answer a. The signal sequence on proteins destined for these organelles is recognized by a receptor protein in the outer membrane of these organelles. b. After a protein moves through the protein translocator in the outer membrane of these organelles, the protein diffuses in the intermembrane space until it encounters a protein translocator in the inner membrane. c. Proteins that are transported into these organelles are unfolded as they are being transported. d. Signal peptidase will remove the signal sequence once the protein has been imported into these organelles.

Answer 89

After a protein moves through the protein translocator in the outer membrane of these organelles, the protein diffuses in the intermembrane space until it encounters a protein translocator in the inner membrane.

Question 90

Your friend works for a biotechnology company and has discovered a drug that blocks the ability of Ran to exchange GDP for GTP. What is the most likely effect of this drug on nuclear transport? Question 20 Answer a. Nuclear transport receptors would be unable to bind cargo. b. Nuclear transport receptors would be unable to enter the nucleus. c. Nuclear transport receptors would be unable to release their cargo in the nucleus. d. Nuclear transport receptors would interact irreversibly with the nuclear pore fibrils.

Answer 90

Nuclear transport receptors would be unable to release their cargo in the nucleus.

Question 91

Which of the following does NOT occur when the unfolded protein response is activated in a cell? Question 21 Answer a. the production of more ER membrane b. the production of more chaperone proteins c. the detection of misfolded proteins by receptors in the cytosol d. the activation of gene regulatory proteins in the cytosol

Answer 91

the detection of misfolded proteins by receptors in the cytosol

Question 92

Which of the following processes should a cell activate to remove a worn-out mitochondrion from its cytoplasm? Question 22 Answer a. exocytosis b. pinocytosis c. autophagy d. phagocytosis

Answer 92

autophagy

Question 93

A large protein that passes through the nuclear pore must have an appropriate Question 23 Answer a. sorting sequence, which typically contains the positively charged amino acids lysine and arginine. b. sorting sequence, which typically contains the hydrophobic amino acids leucine and isoleucine. c. sequence to interact with the nuclear fibrils. d. Ran-interacting protein domain.

Answer 93

sorting sequence, which typically contains the positively charged amino acids lysine and arginine.

Question 94

Which of the following choices reflects the appropriate order of locations through which a newly synthesized protein destined for the plasma membrane travels? Question 24 Answer a. lysosome → endosome → plasma membrane b. ER → lysosome → plasma membrane c. Golgi → lysosome → plasma membrane d. ER → Golgi → plasma membrane

Answer 94

ER → Golgi → plasma membrane

Question 95

Studies of pinocytosis in macrophages show that these cells “drink” a volume of fluid equal to 25% of their total volume every hour. Which of the following processes is thought to balance this fluid intake activity to keep the cell’s volume relatively constant over time? Question 25 Answer a. transcytosis b. phagocytosis c. exocytosis d. osmosis

Answer 95

Exocytosis

Question 96

An individual transport vesicle Question 26 Answer a. contains only one type of protein in its lumen. b. will fuse with only one type of target membrane. c. is endocytic if it is traveling toward the plasma membrane. d. is enclosed by a membrane with the same lipid and protein composition as the membrane of the source organelle.

Answer 96

will fuse with only one type of target membrane.

Question 97

Which of the following statements about peroxisomes is FALSE? Question 27 Answer a. Most peroxisomal proteins are synthesized in the ER. b. Peroxisomes synthesize phospholipids for the myelin sheath. c. Peroxisomes contain enzymes that help inactivate toxins. d. Proteins do not need to unfold to enter the peroxisome.

Answer 97

Most peroxisomal proteins are synthesized in the ER.

Question 98

Which of the following statements about membrane-enclosed organelles is true? Question 28 Answer a. In a typical cell, the area of the endoplasmic reticulum membrane far exceeds the area of plasma membrane. b. The nucleus is the only organelle that is surrounded by a double membrane. c. Other than the nucleus, most organelles are small, and thus, in a typical cell, only about 10% of a cell’s volume is occupied by membrane-enclosed organelles; the other 90% of the cell volume is the cytosol. d. The nucleus is the only organelle that contains DNA.

Answer 98

In a typical cell, the area of the endoplasmic reticulum membrane far exceeds the area of plasma membrane.

Question 99

Lysosomal enzymes are synthesized in the ER and routed through the Golgi apparatus. Which of the following signals diverts these proteins out of the secretory pathway so that they reach the lysosome instead? Question 29 Answer a. a phosphate group added to a serine side chain b. a ubiquitin tag added in the cytosol c. a secondary amino acid targeting signal d. a mannose-6-phosphate sugar added in the Golgi

Answer 99

a mannose-6-phosphate sugar added in the Golgi

Question 100

Which of the following statements about a protein in the lumen of the ER is FALSE? Question 30 Answer a. A protein in the lumen of the ER is synthesized by ribosomes on the ER membrane. b. Some of the proteins in the lumen of the ER can end up in the extracellular space. c. Some of the proteins in the lumen of the ER can end up in the lumen of an organelle in the endomembrane system. d. Some of the proteins in the lumen of the ER can end up in the plasma membrane.

Answer 100

Some of the proteins in the lumen of the ER can end up in the plasma membrane.