Chapter 9 – Cellular Respiration and Fermentation

The glucose molecule has a large quantity of energy in its _____.

A) C—H bonds

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

B) catabolic pathways

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

B) loses electrons and loses potential energy

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

A) C6H12O6 is oxidized and O2 is reduced.

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

C) oxidized

Which of the following statements about NAD+ is true?

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

How many oxygen molecules (O2) are required each time a molecule of glucose (C6H12O6) is completely oxidized to carbon dioxide and water via aerobic respiration?

C) 6

What is the major adaptive advantage of cellular respiration?

C) produce adenosine triphosphate (ATP)

What kind of molecules serve as electron acceptors in cellular respiration?

D) molecules with low potential energy

Why might adding inorganic phosphate, to a reaction mixture where glycolysis is rapidly proceeding, help sustain the metabolic pathway?

C) The metabolic intermediates of glycolysis are phosphorylated.

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

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

B) glycolysis

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

E) 100%

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

C) retained in the two pyruvates

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

C) NADH and pyruvate

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

B) 2 NADH, 2 pyruvate, and 2 ATP

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

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

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

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

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

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

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

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

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.

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

B) low; inhibited

During cellular respiration, acetyl CoA accumulates in which location?

E) mitochondrial matrix

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

D) all cells all the time

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 _____.

D) NADH

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

B) NADH and FADH2

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.

A substrate-level phosphorylation occurs in the citric acid cycle when _____.

A) GDP is phosphorylated to produce GTP

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

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

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

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

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?

C) Oxaloacetate will accumulate and citric acid will decrease.

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)?

D) 3 ATP, 6 CO2, 9 NADH, and 3 FADH2

Which of the following statements about cellular metabolism is FALSE?

B) Citric acid cycle activity is dependent solely on availability of substrate; otherwise it is unregulated.

Which of the following events takes place in the electron transport chain?

C) the extraction of energy from high-energy electrons remaining from glycolysis and the citric acid cycle

C6H12O6 (glucose) + 6 O2 → 6 CO2 + 6 H2O Where is most of the water in this reaction produced?

D) in the electron transport chain

The energy of electron transport serves to move (translocate) protons to the outer mitochondrial compartment. How does this help the mitochondrion produce ATP?

B) The translocation of protons sets up the electrochemical gradient that drives ATP synthesis in the mitochondria.

The constituents of the electron transport chain have similar capabilities, with the exception of ubiquinone (coenzyme Q). What is different about ubiquinone?

D) Ubiquinone is not a protein, is lipid soluble, and can move through the inner mitochondrial membrane.

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

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

Inside an active mitochondrion, most electrons follow which pathway?

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

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

D) mitochondrial intermembrane space

Which of the following produces the most ATP when glucose (C6H12O6) is completely
oxidized to carbon dioxide and water?

E) oxidative phosphorylation (chemiosmosis)

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 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.

Chemiosmotic ATP synthesis (oxidative phosphorylation) occurs in _____.

D) all respiring cells, both prokaryotic and eukaryotic, using either oxygen or other electron acceptors

The accompanying figure shows the electron transport chain. Which of the following is the combination of substances that is initially added to the chain?

D) NADH, FADH2, and O2

Which of the following most accurately describes what is happening along the electron transport chain in the accompanying figure?

B) Each electron carrier alternates between being reduced and being oxidized.

In mitochondria, exergonic redox reactions _____.

C) provide the energy that establishes the proton gradient

When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs?

A) The pH of the matrix increases.

Why are fermentation reactions important for cells?

B) They regenerate NAD+ so that glycolysis can continue to operate.

Which metabolic pathway is common to both cellular respiration and fermentation?

D) glycolysis

The ATP made during fermentation is generated by _____.

B) substrate-level phosphorylation

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

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

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 _____.

E) is a facultative anaerobe

A mutation in yeast makes it unable to convert pyruvate to ethanol. How will this mutation affect these yeast cells? The mutant yeast cells will _____.

A) be unable to grow anaerobically

What carbon source(s) can yeast cells metabolize under anaerobic conditions to make ATP?

A) glucose

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

A) glycolysis and fermentation

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

The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is _____.

A) oxygen