Deck 7: How Cells Harvest Energy

Question 1

What must happen to amino acids before they can be used in catabolic reactions?

A)They must be decarboxylated
B)They must be deoxygenated
C)They must be dehydrogenated
D)They must be deaminated

Answer 1

D

Question 2

A human cell has a mutation in the gene that encodes the enzyme that generates lactate from pyruvate, rendering that enzyme completely non-functional.Assuming that there is ample glucose present, how would this cell generate energy in the presence of oxygen?

A)Glycolysis coupled with ethanol fermentation
B)Aerobic respiration
C)Primarily through the break down of proteins into amino acids
D)This cell would have no way to generate energy under these conditions because it cannot carry out the reactions needed for glycolysis

Answer 2

B

Question 3

How and where is ATP made in a eukaryotic cell?

A)ATP is only made in the mitochondria in response to chemiosmosis.
B)ATP is made in all compartments of the cell in response to endergonic reactions and is used to drive exergonic reactions in the cell.
C)ATP can be made by direct phosphorylation of ADP in the cytoplasm, and by an enzyme complex that uses the energy from a proton gradient to drive ATP synthesis in the mitochondria.It can also be made in other locations in the cell, depending on the cell type.
D)ATP can be made by an enzyme complex that uses the energy of protons moving down their concentration gradient from the mitochondrial matrix to the cytoplasm to make the ATP.

Answer 3

C

Question 4

It is thought that the oldest stage of cellular respiration from an evolutionary perspective is

A)the krebs cycle.
B)the electron transport chain.
C)fermentation.
D)glycolysis.

Question 5

This process is common to all living cells:

A)Glycolysis
B)Alcohol fermentation
C)The Krebs cycle
D)Electron transport chain reactions

Question 6

If you take into account the amount of ATP generated by ATP synthase per molecule of NADH produced in aerobic respiration, the net number of ATP molecules produced by substrate-level phosphorylation, and the fact that NADH molecules produced in the cytoplasm have to be transported into the mitochondria, what is the predicted energy yield of glycolysis in eukaryotic cells?

A)2 ATP
B)5 ATP
C)7 ATP
D)32 ATP

Question 7

In glycolysis, a major portion of the energy remains in the final product, which is called

A)glucose.
B)citrate.
C)glyceraldehyde 3-phosphate (G3P).
D)pyruvate.

Question 8

What molecule can oxidize NADH?

A)Acetaldehyde
B)Lactate
C)Ubiquinone
D)Glucose

Question 9

What oxidizing agent is used to temporarily store high energy electrons harvested from glucose molecules in a series of gradual steps in the cytoplasm?

A)FADH₂
B)ADP
C)NAD⁺
D)Oxygen

Question 10

Organisms that can manufacture their own chemical energy are called ____________.

A)autotrophs
B)heterotrophs
C)oligotrophs
D)chemotrophs

Question 11

Organisms that depend on the energy stored in chemical bonds by other organisms for their food energy are called ____________.

A)Autotrophs
B)Heterotrophs
C)Oligotrophs
D)Chemotrophs

Question 12

When oxygen is unavailable during heavy exercise what process do muscle cells use for energy generation?

A)Glycolysis coupled with alcohol fermentation
B)Anaerobic respiration
C)Aerobic respiration
D)Glycolysis coupled with lactate fermentation

Question 13

During what step of glycolysis are two ATP molecules required?

A)Cleavage and rearrangement
B)Glucose priming
C)Oxidation
D)Pyruvate formation

Question 14

One way to generate acetyl-CoA is to convert pyruvate into acetyl-CoA by stripping off a CO₂ molecule.The removal of CO₂ is referred to as what type of reaction?

A)Decarboxylation
B)Glycolytic
C)Carboxylation
D)Acetylation

Question 15

All of the reactions of cellular respiration that occur after glycolysis take place in what part of the eukaryotic cell?

A)The chloroplast
B)The nucleus
C)The mitochondria
D)The plasma membrane

Question 16

In the reaction: C₄H₆O₄ + FAD $\rightarrow$ C₄H₄O₄ + FADH₂, what type of reaction took place to remove the protons from C₄H₆O₄?

A)Decarboxylation
B)Reduction
C)Dehydrogenation
D)Oxidation

Question 17

What stage of cellular respiration can occur in human cells with or without oxygen present?

A)The Krebs cycle
B)Glycolysis
C)The electron transport chain
D)Pyruvate oxidation

Question 18

In animals that take in oxygen from their environment, glucose is broken down into carbon dioxide and water in a process called

A)anaerobic respiration.
B)organic compound respiration.
C)glucose respiration.
D)aerobic respiration.

Question 19

Many types of cancer cells have been detected to secrete significant levels of lactate.Do you think these cells are likely undergoing beta-oxidation?

A)Yes, because beta-oxidation can generate intermediates that would lead to the production of lactate.
B)No, because if lactate is being produced, the cell is not likely making use of the pathways needed to make use of the products of beta-oxidation.
C)Yes, because lactate stimulates beta-oxidation.
D)No, because lactate is consumed in beta-oxidation

Question 20

In aerobic respiration, chemiosmotic generation of ATP is driven by:

A)P_i transfer through the plasma membrane.
B)the Na⁺/K⁺ pump.
C)a difference in H⁺ concentration on the two sides of the inner mitochondrial membrane.
D)osmosis of macromolecules.

Question 21

Aerobic respiration involves the transfer of many electrons from glucose to electron carriers such as NAD⁺ over a series of multiple steps.Ultimately though, it is the reaction of glucose with oxygen to generate carbon dioxide, water and energy.Why doesn't glucose react directly with oxygen in cells?

A)Oxygen cannot accept electrons, and thus an electron carrier like NAD⁺ is needed.
B)Oxygen and glucose are localized in different subcellular compartments.
C)The direct reaction of oxygen with glucose would be extremely destructive to cells.
D)The reaction of oxygen with glucose is not spontaneous.

Question 22

What is common to all of the oxidation reactions in the Krebs cycle?

A)They all lead to the generation of NADH.
B)They are all decarboxylation reactions.
C)They are all characterized by a loss of electrons from an organic molecule coupled to the reduction of an electron acceptor.
D)They all lead to substrate-level phosphorylation of ADP to generate ATP. While all of the oxidation reactions are characterized by the donation of electrons from an organic molecule to an electron acceptor, they are not all decarboxylation reactions, nor do they all involve the generation of NADH.The third oxidation reaction is not a decarboxylation reaction, and involves the generation of FADH₂.None of the oxidation reactions directly induce substrate-level phosphorylation of ADP.

Question 23

A biochemist wants to control the initial substrate-level phosphorylation that occurs in the tracheal cells of grasshoppers once glucose has crossed the plasma membrane.He has access to the following inhibitors: Rotenone - an electron transport chain inhibitor, Oligomycin - an ATP synthase inhibitor, and TLN-232, an inhibitor of glycolysis.Which inhibitor should he use to slow down initial substrate-level phosphorylation that occurs once glucose has crossed the plasma membrane?

A)Rotenone
B)Oligomycin
C)TLN-232
D)None of these inhibitors would be effective in preventing substrate-level phosphorylation

Question 24

To form NADH from NAD⁺, two electrons and a proton are removed from an organic molecule.What term best describes the reaction in which electrons and a proton are removed from an organic molecule?

A)Condensation
B)Reduction
C)Dehydrogenation
D)Decarboxylation

Question 25

If citrate levels are high in the cell, but ATP levels are low, what do you think will happen in the cell?

A)In the presence of glucose, glycolysis will run to generate energy for the cell, but the Krebs cycle will be inhibited.
B)Glycolysis will be inhibited, but the Krebs cycle will be functional, allowing it to be utilized to breakdown acetyl-CoA generated from beta-oxidation.
C)The electron transport chain will be inhibited, causing a build-up of NADH and FADH₂.This will inhibit the Krebs cycle, but in the presence of glucose, glycolysis will still run coupled with fermentation to regenerate NAD⁺.
D)Glycolysis and the Krebs cycle will both be inhibited, thus under these conditions there will be no mechanism to generate ATP.

Question 26

Cardiac muscle cells need to generate significant amounts of ATP to allow for constant contractile activity.As a result, they primarily depend upon beta-oxidation of fatty acids, which has a higher energy yield than the catabolism of glucose.What would be the ATP yield for beta-oxidation of a hypothetical 10-carbon fatty acid?

A)32 ATP
B)35 ATP
C)50 ATP
D)62 ATP

Question 27

What are the products of one turn of the Krebs cycle?

A)1 CO₂, 2 NADH, 1 FADH₂, 1 ATP
B)2 CO₂, 3 NADH, 1 FADH₂, 1 ATP
C)2 CO₂, 6 NADH, 2 FADH₂, 2 ATP
D)4 CO₂, 6 NADH, 2 FADH₂, 2 ATP

Question 28

Why is the energy generated from the catabolism of sugars and other macromolecules ultimately harnessed to generate ATP?

A)ATP can be used by cells to drive endergonic reactions
B)ATP can be used to make RNA, which is an energy storage molecule in the cell
C)ATP synthesis is an exergonic reaction
D)ATP is required to generate the proton gradient in the intermembrane space of mitochondria

Question 29

Regardless of the electron or hydrogen acceptor used, one of the products of fermentation is always

A)ADP.
B)ATP.
C)NAD^+.
D)pyruvate.

Question 30

Arsenic poisoning can lead to organ failure and death.Though arsenic can inhibit or interfere with a number of cellular enzymes, arsenic poisoning is thought to be mainly due to indirect inhibition of enzymes involved in both pyruvate oxidation and the Krebs cycle.As a result, this compound must be able to enter which cellular compartment?

A)The cytoplasm
B)The nucleus
C)The intermembrane space of the mitochondria
D)The mitochondrial matrix

Question 31

The energy released in the mitochondrial electron transport chain is used to transport proteins into the.

A)mitochondrial matrix.
B)cytoplasm.
C)endoplasmic reticulum.
D)intermembrane space of the mitochondria.

Question 32

What happens to the oxygen that is used in cellular respiration?

A)It is converted to carbon dioxide
B)It is used to make glucose
C)It is used to make Krebs cycle intermediates
D)It is reduced to form water

Question 33

When substrate-level phosphorylation occurs, it means that:

A)NAD⁺ is converted into NADH.
B)ATP is converted into ADP plus a phosphate group.
C)ADP is converted into ATP by the addition of a phosphate group.
D)NADH is converted into NAD⁺ plus a proton.

Question 34

In the reaction catalyzed by aconitase, the conversion of citrate to isocitrate is inhibited by fluoroacetate.Fluoroacetate is used as a pesticide.Why is this an effective pesticide?

A)It inhibits glycolysis
B)It inhibits pyruvate oxidation
C)It inhibits the Krebs cycle
D)It inhibits the electron transport chain

Question 35

What is the net number of ATP generated directly during glycolysis per molecule of glucose?

A)0
B)2
C)4
D)6

Question 36

If you take into account the amount of ATP generated by ATP synthase per molecule of NADH and per molecule of FADH₂ produced, and the number of ATP molecules produced by substrate-level phosphorylation, what is the predicted energy yield of the Krebs cycle, per molecule of glucose in eukaryotic cells?

A)18 ATP
B)2 ATP
C)10 ATP
D)20 ATP

Question 37

Glucose is not our only food source, nor the only one we can utilize in our bodies to generate energy.Other primary sources of energy include other sugars, proteins, and fats.What metabolic intermediate are fats primarily converted into?

A)Pyruvate
B)Acetyl-CoA
C)Krebs cycle intermediates
D)Electron transport chain components

Question 38

Pyruvate oxidation in eukaryotic cells occurs in the ________.

A)cytoplasm
B)nucleus
C)Golgi body
D)mitochondria

Question 39

The Krebs cycle occurs in the mitochondria.There are nine biochemical reactions involved in the Krebs cycle, and they are highly ordered.Select the correct order.(Note: These are abbreviated and do not show NAD, ADP, ATP, or FAD.)

A)acetyl-CoA joins the Kreb cycle and unites with oxaloacetate $\rightarrow$ forming citrate $\rightarrow$ which forms beta-ketoglutarate $\rightarrow$ which forms succinyl-CoA $\rightarrow$ which forms succinate $\rightarrow$ which forms fumarate $\rightarrow$ which forms malate $\rightarrow$ which forms oxaloacetate
B)acetyl-CoA joins the Kreb cycle and unites with oxaloacetate $\rightarrow$ forming citrate $\rightarrow$ which forms alpha-ketoglutarate $\rightarrow$ which forms succinyl-CoA $\rightarrow$ which forms succinate $\rightarrow$ which forms malate $\rightarrow$ which forms fumarate $\rightarrow$ which forms oxaloacetate
C)acetyl-CoA joins the Kreb cycle and unites with oxaloacetate $\rightarrow$ which forms alpha-ketoglutarate $\rightarrow$ forming citrate $\rightarrow$ which forms succinyl-CoA $\rightarrow$ which forms succinate $\rightarrow$ which forms fumarate $\rightarrow$ which forms malate $\rightarrow$ which forms oxaloacetate
D)acetyl-CoA joins the Kreb cycle and unites with oxaloacetate $\rightarrow$ forming citrate $\rightarrow$ which forms alpha-ketoglutarate $\rightarrow$ which forms succinyl-CoA $\rightarrow$ which forms succinate $\rightarrow$ which forms fumarate $\rightarrow$ which forms malate $\rightarrow$ which forms oxaloacetate

Question 40

As electrons move along the electron transport chain, they lose potential energy.How is the energy that is released used by the cell?

A)The energy is used to transport protons against their concentration gradient
B)The energy is used to pump electrons along the electron transport chain
C)The energy is converted directly into ATP
D)The energy is used to pump NAD⁺ into the cytoplasm so it can be used in glycolysis

Question 41

If ATP synthase had a mutation in the F₁ complex portion of the protein, which function of ATP synthase would most likely be affected?

A)The rotation of the rotor
B)The flow of protons through the channel
C)The conversion of ADP and P_i to ATP
D)The insertion of the enzyme into the membrane

Question 42

In order to lose weight and reduce body fat, a friend of yours has decided to eliminate all fat from his diet, while consuming unrestricted amounts of carbohydrates.What do you think of this idea?

A)It is a good idea, because if your friend doesn't eat any fat, he cannot store any additional fat.
B)It is a bad idea, because consumption of fat is required to provide cofactors for the electron transport chain.
C)It is a good idea, because under conditions where ATP levels are low in cells, carbohydrates will be stored, and fat stores will be catabolized via beta-oxidation to generate energy.
D)It is a bad idea, because if ATP levels are high in cells, excess acetyl-CoA from the metabolism of carbohydrates can be used for fatty acid synthesis.

Question 43

Your friend is having difficulty keeping track of the energy flow from glucose through glycolysis, the Krebs cycle and electron transport.Your best advice would be to

A)follow ATP production.
B)follow the protons.
C)follow NAD⁺ production.
D)follow the electrons.

Question 44

You decide to go on vacation in the mountains, where you are staying in a cabin.Unfortunately, when you turn on the water in the cabin you smell hydrogen sulfide (H₂S) gas.After some research, you find out that the H₂S may be due to the presence of sulfur bacteria living in your pipes.What molecule do these bacteria use as an electron acceptor?

A)O₂
B)H₂0
C)SO₄
D)H₂S

Question 45

What is the oxidized form of the most common electron carrier that is needed for both glycolysis and the Krebs cycle?

A)ATP
B)FAD
C)pyruvate
D)NAD⁺

Question 46

Why are the components of the electron transport chain embedded in the inner mitochondrial membrane rather than floating freely in the cytoplasm of mitochondrial matrix?

A)To generate and maintain the proton gradient essential for ATP production.
B)To separate the ATP from the ADP.
C)Because electrons cannot float in the matrix.
D)Because NADH cannot localize to the mitochondrial matrix.

Question 47

Cytochromes contain a heme group similar to that in hemoglobin.The iron atom (Fe) in the center of the group can be oxidized and reduced.If someone was suffering from iron deficiency anemia, what stage of cellular respiration would be most affected?

A)Glycolysis
B)The Krebs cycle
C)The electron transport chain
D)Fermentation

Question 48

As a forensic pathologist, you have just completed an autopsy of a poisoning victim.After a thorough examination, you conclude that the victim died of cyanide poisoning.You know that cyanide binds to the cytochrome oxidase complex, and therefore list the official cause of death as suffocation due to cyanide exposure.However, if you wanted to provide a more technical explanation as to the cause of death, which process was specifically inhibited directly by cyanide?

A)The reduction of NAD⁺
B)The oxidation of FADH₂
C)All proton pumping into the intermembrane space
D)The formation of water from oxygen

Question 49

What aspect of cellular respiration occurs in the cytoplasm in eukaryotic cells?

A)Glycolysis
B)Pyruvate oxidation
C)The Krebs cycle
D)The electron transport chain

Question 50

How many oxidation reactions occur during the Krebs cycle?rev: 02_07_2014_QC_44516

A)1
B)2
C)4
D)6

Question 51

Phosphofructokinase is regulated by a number of factors, including high levels of ATP.Why is this enzyme regulated by ATP levels?

A)If ATP levels are high, this provides a mechanism to directly inhibit the Krebs cycle, thus preventing further generation of NADH, FADH₂ and ATP molecules that are not needed.
B)If ATP levels are high, it is important to directly inhibit the reaction that commits the substrate to glycolysis to allow the substrate to be available for other reactions, since the cell has ample energy.
C)If ATP levels are high, it is important to inhibit ATP synthase, and phosphofructokinase directly inhibits ATP synthase.
D)If ATP levels are high, this provides a mechanism to directly inhibit the electron transport chain, thus preventing the formation of a proton gradient in the intermembrane space of mitochondria.

Question 52

In the absence of oxygen, can cells utilize the electron transport chain?

A)Yes, all cells can make use of the electron transport chain in the absence of oxygen via fermentation.
B)No, oxygen is a required cofactor for the complexes in the electron transport chain.
C)Yes, in the case that a cell can use a terminal electron acceptor other than oxygen, it can make use of the electron transport chain.
D)No, oxygen is the primary electron acceptor in electron transport chains in all cell types.

Question 53

What important metabolic intermediate does not cross the inner membrane of the mitochondria?

A)ATP
B)Acetyl-CoA
C)Pyruvate
D)Oxygen

Question 54

What would be the ATP yield for a molecule that is catabolized to form one molecule of pyruvate in a eukaryotic cell?

A)10 ATP
B)12.5 ATP
C)25 ATP
D)30 ATP

Question 55

Many of the antiviral drugs currently used to treat HIV/AIDS also interfere with an enzyme that helps mitochondria multiply.Treatment can therefore result in a decrease in the number of mitochondria found in certain tissues.Given this information, what might you expect to see in patients treated with antiviral drugs?

A)An increase in oxidative phosphorylation
B)An increase in phosphofructokinase activity
C)An increase in NADH dehydrogenase activity
D)An increase in lactic acid levels