Ch. 13

Question 1

The energy released by oxidizing glucose is saved in the high-energy bonds of

Answer 1

ATP and other activated carrier molecules

Question 2

Sugars derived from food are broken down by

Answer 2

glycolysis, the citric acid cycle, and oxidative phosphorylation

Question 3

Which of the following describes a breakdown process in which enzymes degrade complex molecules into simpler ones?

Answer 3

Catabolism

Question 4

Which of the following locations is NOT used for the digestion of polymeric food molecules into monomeric subunits? A. Extracellular space (the lumen of intestines, for example) B. The cytosol of a cell C. Lysosomes

Answer 4

B. The cytosol of a cell

Question 5

Where does the oxidative breakdown of food molecules occur in a eukaryotic cell?

Answer 5

Mitochondria

Question 6

Which of the following generates the largest amount of ATP? A. Glycolysis B. The citric acid cycle C. The electron transport chain

Answer 6

C. The electron transport chain

Question 7

The end products of glycolysis are:

Answer 7

pyruvate, ATP, and NADH

Question 8

Which of the following is NOT required for glycolysis to occur? A. NAD+ B. ATP C. O2 D. ADP

Answer 8

O2

Question 9

.How much ATP must be invested during the first part of glycolysis for each molecule of glucose broken down?

Answer 9

2 ATP

Question 10

.From one glucose molecule, how much net energy (in the form of ATP and NADH) is produced during glycolysis?

Answer 10

2 ATP, 2 NADH

Question 11

The synthesis of ATP in glycolysis occurs by:

Answer 11

substrate-level phosphorylation

Question 12

For many anaerobic microorganisms, which metabolic pathway is the principle source of ATP? A. Glycolysis B. The citric acid cycle C. The electron transport chain

Answer 12

Glycolysis

Question 13

Under anaerobic conditions, which metabolic pathway regenerates the supply of NAD+ for glycolysis? A. The citric acid cycle B. The formation of acetyl CoA C. Fermentation D. The electron transport chain

Answer 13

Fermentation

Question 14

What does it mean for a bond to be “high energy,” such as between phosphate groups in ATP?

Answer 14

The hydrolysis of such a bond is particularly energetically favorable.

Question 15

Which of the following is true? A. Sugars are converted to Acetyl CoA in the mitochondria; fats are converted to Acetyl CoA in the cytosol. B. Fats are converted to Acetyl CoA in the mitochondria; sugars are converted to Acetyl CoA in the cytosol. C. Sugars and fats are both converted to Acetyl CoA in the mitochondria. D. Sugars are converted to Acetyl CoA but fats are not.

Answer 15

C. Sugars and fats are both converted to Acetyl CoA in the mitochondria.

Question 16

When fatty acids are oxidized to acetyl CoA, each cycle of the reaction removes how many carbon atoms from the fatty acid molecule?

Answer 16

2

Question 17

Although the citric acid cycle itself does not use O2, it requires a functioning electron transport chain (which uses O2) in order to regenerate which molecule for further use in the citric acid cycle? A. NADH B. NAD+ C. H2O D. ATP E. ADP

Answer 17

B. NAD+

Question 18

The citric acid cycle converts the carbon atoms in acetyl CoA to which of the following? A. Pyruvate B. Citrate C. CO2 D. CH4

Answer 18

CO2

Question 19

.Intermediates formed in glycolysis and the citric acid cycle are used by the cell to synthesize: A. (A) amino acids. B. (B) nucleotides. C. (C) lipids. D. All of the above E. A and B, but not C

Answer 19

amino acids. nucleotides. lipids

Question 20

The NADH generated during glycolysis feeds its high energy electrons to:

Answer 20

the electron transport chain.

Question 21

In eukaryotic cells, what is the final electron acceptor in the electron transport chain?

Answer 21

O2

Question 22

In the electron transport chain, the oxygen atoms in O2 become part of which of the following molecules?

Answer 22

H2O molecules

Question 23

The complete oxidation of glucose to H2O and CO2 produces about how many molecules of ATP per molecule of glucose?

Answer 23

30

Question 24

T or F: Metabolism can be tightly regulated because the substrates involved in these reactions are each recognized by a single, unique enzyme.

Answer 24

False

Question 25

What does the term gluconeogenesis refer to?

Answer 25

The synthesis of glucose from small organic molecules such as pyruvate

Question 26

In humans and other mammals, gluconeogenesis occurs mainly in which type of cells?

Answer 26

Liver cells

Question 27

After a normal overnight fast, most of the acetyl CoA entering the citric acid cycle is derived from what type of molecule?

Answer 27

Fatty acids

Question 28

In plants, fats and starch are stored in which part of the cell?

Answer 28

Chloroplast

Question 29

When nutrients are plentiful, plants can store glucose as:

Answer 29

Starch

Question 30

When food is plentiful, animals can store glucose as:

Answer 30

glycogen

Question 31

If a cell is deprived of oxygen, can it continue to produce energy from the breakdown of glucose? Explain.

Answer 31

Yes. In aerobic cells, glucose is broken down by a series of chemical reactions, starting with glycolysis and ending with oxidative phosphorylation. The bulk of the energy produced by glucose breakdown is generated by oxidative phosphorylation, which requires oxygen. In the absence of oxygen glucose can still be broken down by glycolysis to produce smaller amounts of ATP, but the NAD+ required to keep glycolysis running is primarily generated by oxidative phosphorylation. Thus when no oxygen is present, NAD+ is instead replenished by fermentation reactions that both break down the pyruvate produced by glycolysis and generate NAD+. In this way, aerobic cells can continue to generate energy from glucose, albeit a much smaller amount of energy, when oxygen is scarce.

Question 32

In the absence of oxygen, cells consume glucose at a high, steady rate. When oxygen is added, glucose consumption drops precipitously and is then maintained at the lower rate. Why is glucose consumed at a high rate in the absence of oxygen and at a low rate in its presence?

Answer 32

In the absence of oxygen the energy needs of the cell must be met by fermentation to lactate, which requires a high rate of flow through glycolysis to generate sufficient ATP. When oxygen is added, the cell can generate ATP by oxidative phosphorylation, which generates ATP much more efficiently than glycolysis. Thus, less glucose is needed to supply ATP at the same rate.