7 Cellular Respiration and Fermentation

Question 1

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

Answer 1

loses electrons and loses potential energy.

Question 2

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

Answer 2

C6H12O6 is oxidized and O2 is reduced.

Question 3

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

Answer 3

oxidized.

Question 4

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

Answer 4

reduced.

Question 5

Where does glycolysis take place in eukaryotic cells?

Answer 5

cytosol

Question 6

An electron loses potential energy when it

Answer 6

shifts to a more electronegative atom

Question 7

Why are carbohydrates and fats considered high energy foods?

Answer 7

They have a lot of electrons associated with hydrogen.

Question 8

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

Answer 8

100% (~90%)

Question 9

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

Answer 9

NADH and pyruvate

Question 10

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

Answer 10

2 NADH, 2 pyruvate, and 2 ATP.

Question 11

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

Answer 11

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

Question 12

Which of the following intermediary metabolites enters the citric acid cycle and is formed, in part, by the removal of a carbon (CO2) from one molecule of pyruvate?

Answer 12

acetyl CoA

Question 13

How many carbon atoms are fed into the citric acid cycle as a result of the oxidation of one molecule of pyruvate?

Answer 13

two

Question 14

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

Answer 14

oxidation of pyruvate to acetyl CoA and the citric acid cycle

Question 15

Where are the proteins of the electron transport chain located?

Answer 15

mitochondrial inner membrane

Question 16

In cellular respiration, the energy for most ATP synthesis is supplied by

Answer 16

a proton gradient across a membrane

Question 17

The primary role of oxygen in cellular respiration is to

Answer 17

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

Question 18

Inside an active mitochondrion, most electrons follow which pathway?

Answer 18

citric acid cycle → NADH → electron transport chain → oxygen

Question 19

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

Answer 19

mitochondrial intermembrane space

Question 20

The direct energy source that drives ATP synthesis during respiratory oxidative phosphorylation in eukaryotic cells is

Answer 20

the proton-motive force across the inner mitochondrial membrane

Question 21

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

Answer 21

creation of a proton-motive force.

Question 22

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,?

Answer 22

6

Question 23

Which of the following produces the most ATP when glucose (C6H12O6) is completely oxidized to carbon dioxide (CO2) and water?

Answer 23

oxidative phosphorylation (chemiosmosis)

Question 24

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

Answer 24

60-64

Question 25

Chemiosmotic ATP synthesis (oxidative phosphorylation) occurs in

Answer 25

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

Question 26

What is proton-motive force?

Answer 26

the force exerted on a proton by a transmembrane proton concentration gradient

Question 27

Which of the following best describes the main purpose of the combined processes of glycolysis and cellular respiration?

Answer 27

transforming the energy in glucose and related molecules in a chemical form that cells can use for work

Question 28

In the combined processes of glycolysis and cellular respiration, what is consumed and what is produced?

Answer 28

Glucose is consumed, and carbon dioxide is produced.

Question 29

Which of the following describes the process of glycolysis?

Answer 29

It represents the first stage in the chemical oxidation of glucose by a cell.

Question 30

In the citric acid cycle, ATP molecules are produced by _____.

Answer 30

substrate-level phosphorylation

Question 31

A glucose molecule is completely broken down to carbon dioxide and water in glycolysis and the citric acid cycle, but together these two processes yield only a few molecules of ATP. What happened to most of the energy that the cell obtains from the oxidation of glucose?

Answer 31

The electrons obtained from the oxidation of glucose are temporarily stored in NADH and FADH2. The energy derived from the oxidation of NADH and FADH2 is used to drive the electron transport chain and chemiosmotic synthesis of ATP.

Question 32

In cellular respiration, most ATP molecules are produced by _____.

Answer 32

oxidative phosphorylation

This process utilizes energy released by electron transport.

Question 33

The final electron acceptor of cellular respiration is _____.

Answer 33

oxygen

Oxygen is combined with electrons and hydrogen to form water.

Question 34

During electron transport, energy from _____ is used to pump hydrogen ions into the _____.

Answer 34

NADH and FADH2 … intermembrane space

Question 35

The proximate (immediate) source of energy for oxidative phosphorylation is _____.

Answer 35

kinetic energy that is released as hydrogen ions diffuse down their concentration gradient

Question 36

In muscle cells, fermentation produces _____.

Answer 36

lactate and NAD+

Question 37

In fermentation _____ is reduced and _____ is oxidized.

Answer 37

pyruvate … NADH

The pyruvate from glycolysis is reduced to either lactate or ethanol, and NADH is oxidized to NAD+.

Question 38

Which molecule is metabolized in a cell to produce energy for performing work?

Answer 38

Glucose is used to produce high-energy ATP in a cell

Question 39

True or false? The potential energy in an ATP molecule is derived mainly from its three phosphate groups.

Answer 39

True

Question 40

Which step of the cellular respiration pathway can take place in the absence of oxygen?

Answer 40

Glycolysis can take place in the absence of oxygen; its product, pyruvate, enters the cellular respiration pathway or undergoes fermentation depending on the availability of oxygen.

Question 41

Into which molecule are all the carbon atoms in glucose ultimately incorporated during cellular respiration?

Answer 41

All of the carbon atoms in glucose are incorporated into carbon dioxide: Two molecules are formed as pyruvate is converted to acetyl CoA, and four molecules are formed during the Krebs cycle.

Question 42

True or false? The reactions that generate the largest amounts of ATP during cellular respiration take place in the mitochondria.
True or false? The reactions that generate the largest amounts of ATP during cellular respiration take place in the mitochondria.

Answer 42

True
Glycolysis takes place in the cytoplasm, whereas the Krebs cycle and the electron transport chain, which generate the largest amounts of ATP during cellular respiration, take place in the mitochondria.