Bio 10 - Energy Metabolism

Question 1

Which type of pyruvate is used to feed into the TCA cycle?

Answer 1

The pyruvate that has been converted to Acetyl-CoA.

Question 2

What are the co-factors need to make pyruvate to Acetyl-CoA?

Answer 2

[TLC For Nobody] Thiamine pyrophosphate (TPP; the active form of thiamine). Lipoic acid. Coenzyme A (vitamin B5). FAD (vitamin B2). NAD+ (vitamin B3).

Question 3

Which poison can inhibit Lipoic acid?

Answer 3

Arsenic; causes garlic breath, vomiting, rice-water stools.

Question 4

What are the causes of PDH deficiency?

Answer 4

X-linked congenital defect. Acquired defect (arsenic exposure). Deficient in one of the B vitamins (especially B1; thiamine).

Question 5

What does Citrate synthase do?

Answer 5

It converts Acetyl-CoA into citrate in the TCA (Krebs) cycle.

Question 6

What is the rate-limiting enzyme in TCA cycle? What does it do?

Answer 6

It is Isocitrate dehydrogenase. It converts Isocitrate into alpha-ketoglutarate.

Question 7

What does alpha-ketoglutarate dehydrogenase do?

Answer 7

Converts alpha-ketoglutarate into succinyl-CoA. It requires all the same co-factors as pyruvate dehydrogenase (TPP, Lipoic Acid, Coenzyme A, FAD, NAD+).

Question 8

Where does TCA take place?

Answer 8

In the inner mitochondrial membrane.

Question 9

What is Complex I in the mitochondria?

Answer 9

It is NADH reductase. It converts NADH to NAD+, while pumping a H+ ion into the intermembrane space. It also generates an electron that goes into Complex II.

Question 10

Which substances inhibit Complex I?

Answer 10

Amytal. Rotenone. MPP.

Question 11

Which substances inhibit Complex III?

Answer 11

Antimycin A.

Question 12

Which substances inhibit Complex IV?

Answer 12

Cianide. Sodium Azide. Carbon monoxide. Hydrogen Sulfide.

Question 13

Which substances inhibit ATPase?

Answer 13

Oligomycin A.

Question 14

What is an uncoupling agent?

Answer 14

Uncouples the electron transport chain from the ATPase: it increases the permeability of the inner mitochondrial membrane to hydrogen ions, generating more heat in the body.

Question 15

What are three uncoupling agents?

Answer 15

Thermogenin. Aspirin. 2,4-DNP.

Question 16

Why are alanine and glutamine found in such high concentrations in the blood?

Answer 16

They are the two major carriers of nitrogen from tissue.

Question 17

What is generally involved in transamination? What enzyme catalyses this reaction?

Answer 17

Transfer of the amino group of an amino acid to alpha-ketoglutarate to form glutamate. The remaining deaminated amino acid is a ketoacid (such as pyruvate) that is used in energy metabolism. Aminotransferase catalyzes the reaction.

Question 18

How are aminotransferases named?

Answer 18

By donor of the amino group (alanine aminotransferase converts alanine to pyruvate and forms glutamate).

Question 19

In addition to substrates, what is required by all aminotransferases?

Answer 19

Pyridoxal phosphate (a derivative of vitamin B6).

Question 20

What are the two most important amintransferase enzymes? What reactions do they catalyze?

Answer 20

Alanine aminotransferase (ALT): converts alanine + alpha-ketoglutarate into glutamate + pyruvate. Aspartate Aminotransferase (AST): converts Glutamate + Oxaloacetate into alpha-ketoglutarate + Aspartate.

Question 21

What are the two main transporters of nitrogen in the blood?

Answer 21

Alanine. Glutamine.

Question 22

What are the major regulatory enzymes of the citric acid (TCA) cycle?

Answer 22

Citrate synthase. Isocitrate dehydrogenase. Alpha-ketoglutarate dehydrogenase.

Question 23

What are the four things that can be done to pyruvate?

Answer 23

Converted to Oxaloacetate (using pyruvate carboxylase), Acetyl-CoA (using pyruvate dehydrogenase), Lactate (Lactate dehydrogenase), or Alanine (using ALT).