Unit 4: Energy

Question 1

One of the results of the TCA cycle is the ______________?

a) oxidation of NAD+
b) reduction of NAD+
c) oxidation of NADH
d) reduction of NADH

Answer 1

B) reduction of NAD+

Question 2

During aerobic cellular respiration, the carbons present in pyruvate are initially derived from _______ and are ultimately converted to _______

Answer 2

glucose and CO2

Question 3

Which reactant molecule becomes reduced in the following chemical equation?
glyceraldehyde 3-phosphate + NAD+ + Pi –> 1,3-diphsophoglycerate + NADH + H+

Answer 3

NAD+

Question 4

Substrate level phosphorylation…..

a) requires the presence of oxygen as the terminal electron acceptor
b) happens only in the mitochondria, therefore only occurs in eukaryotic cells
c) refers to the enzyme-catalyzed transfer of an activated phosphate group to form a nucleoside triphosphate
d) a and c
e) a b and c

Answer 4

c)

Question 5

Two ATP molecule are ‘spent’ in the energy investment phase of glycolysis. Why is this energy necessary to begin the process of glucose catabolism?

a) It isn’t ; glucose contains 686 kcal/mol in its chemical bonds, so its catabolism is spontaneous
b) it is needed to generate the electron carrier NAD+
c) it is needed to prime the enzymes of glycolysis
d) some energy must be invested to make glucose more reactive

Answer 5

d) some energy must be invested to make glucose more reactive

Question 6

What does the enzyme phosphofructokinase catalyze?

Answer 6

phosphorylation of fructose 6-phosphate to form fructose 1,6-biphosphate

Question 7

What compound is most likely to inhibit the pyruvate dehydrogenase enzyme complex through a mechanism of feedback regulation?

Answer 7

NADH

Question 8

Fatty acids are catabolized by a process called beta-oxidation. The end-products of the metabolic pathway are acetyl groups of acetyl CoA molecules. Where would these acetyl groups enter the energy pathway?

Answer 8

Citric Acid Cycle / Krebs Cycle

Question 9

What importance do fermentation reaction give to cells?

Answer 9

Regenerate NAD+

Question 10

In a chloroplast of a plant cell actively engaged in photosynthesis, you would expect the pH to be?

Answer 10

lower in the thylakoid space than in the stroma

Question 11

Why does NADH produce more energy than FADH2?

Answer 11

NADH passes its electrons through 3 proton pumps. FADH2 binds to ubiquinone and passes its electrons through only 2 proton pumps

Question 12

Why does the oxidation of sugar produce less energy than the direct burning of sugar?

Answer 12

Oxidation of sugar it done through a multitude of steps, each having its own activation energies, each losing heat each time

Question 13

Is NADH in an oxidized or reduced form?

Answer 13

Reduced

Question 14

Where does the breakdown of glucose into 2 pyruvate molecules occur?

Answer 14

Cytosol

Question 15

Do all NADH molecules produce the same amount of energy?

Answer 15

NADH molecules produced during the glycolysis stage produce less energy. Because they are made in the cytosol of the cell, they have to be transported over to the mitochondrial membrane to be used in the ETC

Question 16

Where is the Krebs Cycle located?

Answer 16

Mitochondrial matrix

Question 17

What is the major contributor of proton force that is responsible for generating ATP through chemiosmosis?

Answer 17

The charge difference between the intermembrane space (positive) and mitochondrial matrix (negative)

Question 18

Example of a cell that can behave as facultative anaerobes

Answer 18

muscle cells

Question 19

Example of a cell that cannot behave as facultative anaerobe and why?

Answer 19

neuron cells, they require more than the 2 ATP/glucose molecule to keep functioning

Question 20

What are the key differences between chloroplasts and mitochondria?

Answer 20

Chloroplasts are larger, contain thylakoids - only have 1 proton pump (only 1 non-permeable membrane so they can create bigger differences in pH)

Question 21

Why does Krebs Cycle stop when there is no oxygen?

Answer 21

Oxygen is the final acceptor in the ETC. This causes a backup in oxidative phosphorylation, and a buildup of loaded energy carriers that are waiting to be oxidized (FADH2, NADH). Without being able to take off H, the Krebs cycle and the only process that can occur is glycolysis

Question 22

The conversion of pyruvate to acetyl CoA occurs

a) through 4 enzymatic reactions mediated by the pyruvate dehydrogenase complex
b) in the mitochondrial matrix, after moving across the inner and outer mitochondrial membrane
c) In the cytoplasm prior to transport into the mitochondrial matrix
d) to oxide and activate the pyruvate molecule so it can enter the TCA cycle
e) b and d

Answer 22

e)

Question 23

What is the function of coenzyme A in the TCA cycle?

a) Coenzyme for the decarboxylation of pyruvate
b) Coenzyme of redox reactions
c) Coenzyme of dehydration reactions
d) activates a two carbon acyl group derived from pyruvate
e) It prepares NADH and FADH2 for oxidative phosphorylation

Answer 23

d)

Question 24

Following glycolysis and the TCA cycle and before the ETC and oxidative phosphorylation, the carbon skeleton of glucose has been broken down to Co2. Most of the energy from the original glucose at this point is still in the form of:

a) ATP
b) NAD+
c) CO2
d) carbon-hydrogen bonds
e) NADH

Answer 24

e)

Question 25

In the breakdown of glucose, where is most of the water produced from?

a) glycolysis
b) TCA cycle
c) fermentation
d) ETC

Answer 25

d) ETC

Question 26

If glucose is fully labeled with radioactive C-14, what molecule will become radioactive as glycolysis and the TCA cycle are completed?

a) H2O
b) CO2
c) ATP
d) NADH
e) CoA

Answer 26

b)

Question 27

The fermentation pathway allows:

a) the extraction of additional energy through the further oxidation of glucose
b) the glycolytic pathway to continue by providing an alternative electron acceptor for the regeneration of NAD+
c) a mechanism for certain tissues to function under oxygen depleted conditions
d) the TCA cycle to continue to function in the absence of oxygen
e) b and c

Answer 27

e)