Chapter 10: Cell Respiration

Question 1

In the overall process of glycolysis and cellular respiration, __________ is oxidized and __________ is reduced.

Answer 1

glucose … oxygen
In cellular respiration, glucose is oxidized (resulting in the production of carbon dioxide) and oxygen is reduced (resulting in the production of water).

Question 2

Oxygen gas (O2) is one of the strongest oxidizing agents known. The explanation for this is that

Answer 2

the oxygen atom is very electronegative

Question 3

A small amount of ATP is made in glycolysis by which of the following processes?

Answer 3

transfer of a phosphate group from a fragment of glucose to ADP by substrate-level phosphorylation.
Remember that glucose is phosphorylated at the beginning of glycolysis.

Question 4

There is no production of carbon dioxide in glycolysis. Which of the following is the best explanation for this fact?

Answer 4

The products of glycolysis contain the same total number of carbon atoms as in the starting material.

Question 5

Which of the following molecules in the process of glycolysis possesses the most chemical energy

Answer 5

Fructose-1,6-bisphosphate has received two phosphate groups from ATP, conserving some of the energy derived from the hydrolysis of ATP in the fructose-1,6-bisphosphate molecule.

Question 6

Which of the following processes generates most of the NADH that delivers electrons to the electron transport chain?
In an experiment, mice were fed glucose (C6H12O6) containing a small amount of radioactive oxygen. The mice were closely monitored, and after a few minutes radioactive oxygen atoms showed up in __________.

Answer 6

Most of the NADH is produced during the citric acid cycle, along with some FADH2.
CO2

Question 7

In preparing pyruvate to enter the citric acid cycle, which of the following steps occurs?

Answer 7

Pyruvate is oxidized and a molecule of carbon dioxide is removed. The electrons removed in this process are used to reduce NAD+ to NADH.

Question 8

Why is the citric acid cycle called a “cycle”?

Answer 8

The four-carbon acid that accepts the acetyl CoA in the first step of the cycle is regenerated by the last step of the cycle.

Question 9

Where do the reactions of the citric acid cycle occur in eukaryotic cells?
Which of the following represents the major (but not the only) energy accomplishment of the citric acid cycle?

Answer 9

The citric acid cycle, which takes place in the mitochondrial matrix, completes the degradation of glucose.
formation of NADH and FADH2: Each turn of the citric acid cycle releases carbon dioxide, forms one ATP by oxidative phosphorylation, and passes electrons to three NAD+ and one FAD.

Question 10

After completion of the citric acid cycle, most of the usable energy from the original glucose molecule is in the form of __________.

Answer 10

The citric acid cycle produces three NADH per turn of the cycle.

Question 11

The energy given up by electrons as they move through the electron transport chain is used in which of the following processes?

Answer 11

pumping H+ across a membrane: Many of the electron transport molecules in the mitochondrion pump a hydrogen ion into the intermembrane space when they pass an electron along the chain.

Question 12

Energy for synthesizing ATP is obtained by ATP synthase directly from which of the following processes?

Answer 12

the flow of H+ across the inner mitochondrial membrane through the ATP synthase enzyme: Hydrogen ions flow along an electrochemical gradient across the inner mitochondrial membrane. The gradient is the source of the energy for ATP production.

Question 13

When a poison such as cyanide blocks the electron transport chain, glycolysis and the citric acid cycle also eventually stop working. Which of the following is the best explanation for this?

Answer 13

NAD+ and FAD are not available for glycolysis and the citric acid cycle to continue.

Question 14

During aerobic respiration, molecular oxygen (O2) is used for which of the following purposes?

Answer 14

at the end of the electron transport chain to accept electrons and form H2O

Question 15

Electrons are passed from one carrier to another, releasing a little energy at each step.
NADH and FADH2 deliver electrons from the breakdown products of glycolysis and the citric acid cycle to the electron transport chain, which passes these electrons from one molecule to another, releasing a small amount of energy at each step.

Answer 15

etc

Question 16

Which of the following is the source of the energy that produces the chemiosmotic gradient in mitochondria?

Answer 16

movement of electrons down the electron transport chain. Energy from the flow of electrons along the electron transport chain is used to pump hydrogen ions (protons) across the inner mitochondrial membrane, creating the chemiosmotic gradient.

Question 17

In eukaryotic cells, the components of the electron transport chain are located in or on __________.

Answer 17

the inner membrane of the mitochondrion

Question 18

Fermentation is essentially glycolysis plus an extra step in which pyruvate is reduced to form lactate or alcohol and carbon dioxide. This last step __________.

Answer 18

enables the cell to recycle the reduced NADH to oxidized NAD+

Question 19

In glycolysis in the absence of oxygen, cells need a way to regenerate which compound?

Answer 19

NAD+

Question 20

If muscle cells in the human body consume O2 faster than it can be supplied, which of the following is likely to result?
The muscle cells will have more trouble making enough ATP to meet their energy requirements.
The cells will not be able to carry out oxidative phosphorylation.
The cells will consume glucose at an increased rate.
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Answer 20

read

Question 21

When protein molecules are used as fuel for cellular respiration, __________ are produced as waste.

Answer 21

amino groups: The amino group is a residual product of amino acid catabolism.

Question 22

A gram of fat oxidized by respiration produces approximately twice as much ATP as a gram of carbohydrate. Which of the following best explains this observation?

Answer 22

Fats are better electron donors to oxygen than are sugars.
Fats contain more hydrogen and less oxygen than sugars—it is the transfer of electrons from good donors such as hydrogen atoms to good acceptors such as oxygen that provides the energy in respiration.

Question 23

If significant amounts of materials are removed from the citric acid cycle to produce amino acids for protein synthesis, which of the following will result?

Answer 23

Less ATP will be produced by the cell.
Less CO2 will be produced by the cell.
The four-carbon compound that combines with acetyl CoA will have to be made by some other process.