Chapter 10: Carbohydrate Metabolism II: Aerobic Respiration

Question 1

What is the main function of the citric acid cycle?

Answer 1

• Oxidation of acetyl-CoA to CO2 and H2O
• producing NADH and FADH2

Question 2

After glucose undergoes glycolysis, its product, ____________, enters the mitochondrion via active transport and is oxidized and decarboxylated. These reactions are catalyzed by what multienzyme complex?

Answer 2

pyruvate; pyruvate dehydrogenase complex

Question 3

Pyruvate dehydrogenase complex is inhibited by what? What could caused this?

Answer 3

An accumulation of acetyl-CoA and NADH; can occur if ETC is not properly function or is inhibited

Question 4

Coenzyme A is a ____________, which means it contains what functional group?

Answer 4

Thiol; -SH

Question 5

When acetyl-CoA forms, it does so via covalent attachemnt of the ________ group to the -SH group, resulting in the formation of a ________________, which contains sulfur instead of the typical oxygen ester -OR.

Answer 5

acetyl; thioester

Question 6

What are the 3 enzymes that are part of the pyruvate dehydrogenase complex?

Answer 6

1. pyruvate dehydrogenase
2. dihydrolipoyl transacetylase
3. dihydrolipoyl dehydrogenase

Question 7

When pyruvate is oxidized by pyruvate dehydrogenase (PDH), it yields ____, and the remaining 2-carbon molecule binds covalently to ____________ ________________. This is a coenzyme held by noncovalent interactions to PDH. ____ is also required.

Answer 7

CO2; thiamine pyrophosphate; Mg2+

Question 8

The 2-carbon molecule bonded to TPP is oxidized and transferred to ________ acid, a coenzyme bonded to dihydrolipoyl transacetylase. Lipoic acid’s disulfide group acts as an oxidizing agent, creating the ________ group, which is now bonded to lipoic acid via ____________ linkage. Dihydrolipoyl transacetylase catalyzes the ____-____ interaction with the newly formed thioester link, causing transfer of an acetyl group to form ________-________.

Answer 8

lipoic; acetyl; thioester; CoA-SH, acetyl-CoA

Question 9

Flavin adenine dinucleotide is used as a coenzyme in order to reoxidize lipoic acid, allowing lipoic acid to facilitate acetyl-CoA formation in future reactions. As lipoic acid is reoxidized, FAD is reduced to ________, which is later reoxidized to ____, while NAD+ is reduced to ____.

Answer 9

FADH2, FAD, NADH

Question 9

Flavin adenine dinucleotide is used as a coenzyme in order to reoxidize lipoic acid, allowing lipoic acid to facilitate acetyl-CoA formation in future reactions. As lipoic acid is reoxidized, FAD is reduced to ________, which is later reoxidized to ____, while NAD+ is reduced to ____.

Answer 9

FADH2, FAD, NADH

Question 10

Acetyl-CoA is best known as being generated by oxidative decarboxylation of ____________ in the ____________ pathway.

Answer 10

pyruvate; glycolysis

Question 11

Acetyl-CoA can also be made during ________ ________ oxidation. A process called ____________ causes a thioester bond to form between carboxyl groups of fatty acids and CoA-SH.

Answer 11

fatty acid; activation

Question 12

Because activated ________ ________-________ cannot cross the inner mitochondrial membrane, the fatty acyl group is transferred to ____________ via a trans-esterification reaction.

Once acyl- carnitine crosses the inner membrane, it transfers the fatty acyl group to a mitochondrial CoA-SH via another transesterification reaction. Carnitine’s main function is what?

Answer 12

fatty acyl-CoA; carnitine

Fnction is to carry acyl group from cytosolic CoA-SH to a mitochondrial CoA-SH; once acyl-CoA is in the matrix, beta-oxidation can occur

Question 13

Certain ________ ________ can also be used to form acetyl-CoA. They have to lose their ________ group via transamination. Their carbon skeletons can then form ________ ________. This is why they are labeled “ketogenic.”

Answer 13

amino acids; amino; ketone bodies

Question 14

Although acetyl CoA is typically used to produce ____________ when pyruvate dehydrogenase complex is inhibited, the reverse reaction can occur as well, and this produces?

Answer 14

ketones; acetylCoA

Question 15

When alcohol is consumed in moderate amounts, the enzymes ____________ ________________ and ________________ ________________ convert it to acetyl-CoA. This causes ____________ buildup, which inhibits the Krebs Cycle. Acetyl-COA formed by this process is used primarily to synthesize ____________ ____________ because of this.

Answer 15

alcohol dehydrogenase, acetaldehyde dehydrogenase; NADH; fatty acids

Question 16

What is the first step of TCA?

Answer 16

coupling of acetyl-CoA to oxaloacetate

Question 17

Although oxygen is not directly required in TCA, it will not occur anaerobically. Why?

Answer 17

Because NADH and FADH2 are produced, and they will accumulate if the ETC cannot occur due to lack of oxygen.

Question 18

Step 1 of TCA is ________ ____________.

Answer 18

Citrate formation

Question 19

To form citrate, ________-____ and ____________ undergo a condensation reaction to form ________-________, an intermediate. This is then hydrolyzed to yield ________ and ________-________. This is catalyzed by?

Answer 19

acetyl-CoA, oxaloacetate; citryl-CoA; citrate and CoA-SH; citrate synthase

Question 20

Phosphorylation of PDH activates it. This happens when levels of ____ are high.

Answer 20

ATP, because PDH is phosphorylated

Question 21

Pyruvate dehydrogenase is reactivated by pyruvate dehydrogenase ____________ in response to high levels of ________.

Answer 21

phosphatase; ADP

Question 22

What are 3 essential checkpoints that regulate TCA?

Answer 22

1. citrate synthase
2. isocitrate dehydrogenase
3. alpha-ketoglutarate dehydrogenase complex

Question 23

If you pair 2 molecules with different reduction potentials, the molecule with the higher potential will be ____________, while the other molecule will become ____________.

Answer 23

reduced; oxidized

Question 24

What happens in low O2 conditions?

Answer 24

the rate of oxidative phosphorylation decreases and NADH/FADH2 increase as a result