Chapter 9 study Guide

If you were to add one of the eight citric acid cycle intermediates to the culture medium of yeast growing in the laboratory, what do you think would happen to the rates of ATP and carbon dioxide production?

b. The rates of ATP production and carbon dioxide production would both increase.

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

b. accepting electrons at the end of the electron transport chain

In the presence of oxygen, the three-carbon compound pyruvate can be catabolized in the citric acid cycle. First, however, the pyruvate (1) loses a carbon, which is given off as a molecule of CO2, (2) is oxidized to form a two-carbon compound called acetate, and (3) is bonded to coenzyme A. The three listed steps result in the formation of ____.

b. acetyl CoA, NADH, and CO2

The primary role of oxygen in cellular respiration is to ____.

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

Even though plants cells photosynthesize, they still use their mitochondria for oxidation of pyruvate. This will occur in ____.

b. all cells all the time

Substrate-level phosphorylation occurs

.d. in both glycolysis and the citric acid cycle

The oxidation of glucose in the presence of oxygen involves glycolysis, pyruvate oxidation, and the citric acid cycle (Krebs cycle). Some energy is captured in glycolysis when glucose is converted to pyruvate (pyruvic acid). In the citric acid cycle (Krebs cycle), more energy is captured in the form of reduced electron carriers, NADH and FADH2. Select the best explanation for why the eventual reoxidation of NADH and FADH2 is crucial for the continuation of the citric acid (Krebs) cycle.

A) In order for the cycle to continue, oxidized electron carriers must be available.

ATP synthase is a key enzyme of mitochondrial energy conversion. Mitochondrial ATP synthase deficiency is due to a mutation in a gene important for the formation of a subunit in the ATP synthase complex. Scientists could use cells with this gene mutation to investigate which of the following questions?

C) What effect does the mutation have on the amount of ATP synthesized during cellular respiration?

Which of the listed statements describes the results of the following reaction? C6H12O6 + 6 O2→ 6 CO2 + 6 H2O + Energy

C6H12O6 is oxidized and O2 is reduced.

A young dog has never had much energy. He is brought to a veterinarian for help and she decides to conduct several diagnostic tests. She discovers that the dog's 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 the dog's condition?

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

Which electron carrier(s) function in the citric acid cycle?

a. NADH and FADH2

In the presence of oxygen, the three-carbon compound pyruvate can be catabolized in the citric acid cycle. First, however, the pyruvate (1) loses a carbon, which is given off as a molecule of CO2, (2) is oxidized to form a two-carbon compound called acetate, and (3) is bonded to coenzyme A. Which one of the following is formed by the removal of a carbon (as CO2) from a molecule of pyruvate?

a. acetyl CoA

High levels of citric acid inhibit the enzyme phosphofructokinase, a key enzyme in glycolysis. Citric acid binds to the enzyme at a different location from the active site. This is an example of ____.

a. allosteric regulation

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

a. an agent that closely mimics the structure of glucose but is not metabolized

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

a. creation of a proton-motive force

Yeast cells that have defective mitochondria incapable of respiration will be able to grow by catabolizing which of the following carbon sources for energy?

a. glucose

Carbohydrates and fats are considered high-energy foods because they ____.

a. have a lot of electrons associated with hydrogen.

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

a. oxidation of pyruvate to acetyl CoA and the citric acid cycle

What is the oxidizing agent in the following reaction? Pyruvate + NADH + H+→ Lactate + NAD+

a. pyruvate

Most of the CO2 from the catabolism of glucose is released during ____.

a. the citric acid cycle

In the presence of oxygen, the three-carbon compound pyruvate can be catabolized in the citric acid cycle. First, however, the pyruvate (1) loses a carbon, which is given off as a molecule of CO2, (2) is oxidized to form a two-carbon compound called acetate, and (3) is bonded to coenzyme A. Which of the following events takes place in the electron transport chain?

a. the extraction of energy from high-energy electrons remaining from glycolysis and the citric acid cycle

Substrate-level phosphorylation accounts for approximately what percentage of the ATP formed by the reactions of glycolysis?

b. 100%

Starting with one molecule of glucose, the energy-containing products of glycolysis are ____.

b. 2 NADH, 2 pyruvate, and 2 ATP

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

b. 30-32

New biosensors, applied like a temporary tattoo to the skin, can alert serious athletes that they are about to "hit the wall" and find it difficult to continue exercising. These biosensors monitor lactate, a form of lactic acid, released in sweat during strenuous exercise. Which of the statements below is the best explanation of why athletes would need to monitor lactate levels?

b. During anaerobic respiration, lactate levels increase when muscles cells need more energy, however muscles cells eventually fatigue, thus athletes should modify their activities to increase aerobic respiration.

If pyruvate oxidation is blocked, what will happen to the levels of oxaloacetate and citric acid in the citric acid cycle shown in the accompanying figure?

b. Oxaloacetate will accumulate and citric acid will decrease.

Exposing inner mitochondrial membranes to ultrasonic vibrations will disrupt the membranes. However, the fragments will reseal "inside out." The little vesicles that result can still transfer electrons from NADH to oxygen and synthesize ATP. After the disruption, when electron transfer and ATP synthesis still occur, what must be present?

b. all of the electron transport proteins and ATP synthase

The synthesis of ATP by oxidative phosphorylation, using the energy released by movement of protons across the membrane down their electrochemical gradient, is an example of ____.

b. an endergonic reaction coupled to an exergonic reaction

In respiration, beta oxidation involves the ____.

b. breakdown of fatty acids

In chemiosmosis, what is the most direct source of energy that is used to convert ADP + (p)i to ATP?

b. energy released from movement of protons through ATP synthase, down their electrochemical gradient

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

b. glycolysis

The chemiosmotic hypothesis is an important concept in our understanding of cellular metabolism in general because it explains ____.

b. how ATP is synthesized by a proton motive force

Starting with citrate, which of the following combinations of products would result from three acetyl CoA molecules entering the citric acid cycle (see the accompanying figure)?

c. 3 ATP, 6 CO2, 9 NADH, and 3 FADH2

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

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

A cell has enough available ATP to meet its needs for about 30 seconds. What is likely to happen when an athlete exhausts his or her ATP supply?

c. Catabolic processes are activated that generate more ATP.

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

c. FADH2

Why is glycolysis considered to be one of the first metabolic pathways to have evolved?

c. It does not involve organelles or specialized structures, does not require oxygen, and is present in most organisms.

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

c. It increases the surface for oxidative phosphorylation.

The free energy for the oxidation of glucose to CO2 and water is -686 kcal/mol and the free energy for the reduction of NAD+ to NADH is +53 kcal/mol. Why are only two molecules of NADH formed during glycolysis when it appears that as many as a dozen could be formed?

c. Most of the free energy available from the oxidation of glucose remains in pyruvate, one of the products of glycolysis.

Which of the following statements about NAD+ is true?

c. NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.

Following glycolysis and the citric acid cycle, but before the electron transport chain and oxidative phosphorylation, the carbon skeleton of glucose has been broken down to CO2 with some net gain of ATP. Most of the energy from the original glucose molecule at that point in the process, however, is in the form of ____.

c. NADH

Canine phosphofructokinase (PFK) deficiency afflicts Springer spaniels, affecting an estimated 10% of the breed. Given its critical role in glycolysis, one implication of the genetic defect resulting in PFK deficiency in dogs is ____.

c. an intolerance for exercise

Exposing inner mitochondrial membranes to ultrasonic vibrations will disrupt the membranes. However, the fragments will reseal "inside out." The little vesicles that result can still transfer electrons from NADH to oxygen and synthesize ATP. These inside-out membrane vesicles will ____

c. become acidic inside the vesicles when NADH is added

During aerobic respiration, electrons travel downhill in which sequence?

c. glucose ® NADH ® electron transport chain ® oxygen

An organism is discovered that thrives in both the presence and absence of oxygen in the air. Curiously, the consumption of sugar increases as oxygen is removed from the organism's environment, even though the organism does not gain much weight. This organism ____.

c. is a facultative anaerobe

The electron transport chain ____.

c. is a series of redox reactions

Glycolysis is active when cellular energy levels are ____; the regulatory enzyme, phosphofructokinase, is ____ by ATP.

c. low; inhibited

Where are the proteins of the electron transport chain located?

c. mitochondrial inner membrane

During aerobic respiration, H2O is formed. Where does the oxygen atom for the formation of the water come from?

c. molecular oxygen (O2)

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

c. reduced

In glycolysis, for each molecule of glucose oxidized to pyruvate ____.

c. two molecules of ATP are used and four molecules of ATP are produced.

If a cell is able to synthesize 30 ATP molecules for each molecule of glucose completely oxidized to carbon dioxide and water, approximately how many ATP molecules can the cell synthesize for each molecule of pyruvate oxidized to carbon dioxide and water?

d. 14

If glucose is the sole energy source, what fraction of the carbon dioxide exhaled by animals is generated by the reactions of the citric acid cycle?

d. 2/3

The citric acid cycle. For each mole of glucose (C6H12O6) oxidized by cellular respiration, how many moles of CO2 are released in the citric acid cycle (see the accompanying figure)?

d. 4

You have a friend who lost 7 kg (about 15 pounds) of fat on a regimen of strict diet and exercise. How did the fat leave his body?

d. It was released as CO2 and H2O.

Chemiosmotic ATP synthesis (oxidative phosphorylation) occurs in ____.

d. all respiring cells, both prokaryotic and eukaryotic, using either oxygen or other electron acceptors

Fatty acids usually have an even number of carbons in their structures. They are catabolized by a process called beta-oxidation. The end products of the metabolic pathway are acetyl groups of acetyl CoA molecules. These acetyl groups ____

d. directly enter the citric acid cycle

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

d. glycolysis and fermentation

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

d. loses electrons and loses potential energy

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

d. mitochondrial intermembrane space

One function of both alcohol fermentation and lactic acid fermentation is to ____.

d. oxidize NADH to NAD+

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

d. oxidized

When electrons move closer to a more electronegative atom, what happens? The more electronegative atom is ____.

d. reduced, and energy is released