Metabolism

Question 1

When [ammonia] is high, what else will be elevated?

Answer 1

[glutamine]

Question 2

What cofactor does transamination require?

Answer 2

Pyridoxal phosphate, a B6 derivative

Question 3

What stimulates proteolysis?

Answer 3

increased [cortisol]

Question 4

What stimulates the activity of PFK1?

Answer 4

Increased [AMP]

Increased [insulin]

Question 5

What inhibits the activity of PFK1?

Answer 5

Increased [ATP]
Increased [citrate] (synthesized during FA synthesis when energy stores are high)
Increased [glucagon]

Question 6

How are NADH and FADH2 produced?

Answer 6

TCA + glycolysis.

Used in oxidative phosphorylation (ETC)

Question 7

How does a salicylate overdose interrupt metabolic function?

Answer 7

Via uncoupling the synthesis of ATP from the ETC. Proteins create channels or carry H+ across the mitochondrial membrane, dissipating the proton gradient. E- still flow through the ETC complexes, but generate no ATP. Results in increased heat production, increased [ADP], and increased metabolic rate.

Same mechanism as brown fat and dinitrophenol.

Question 8

How does cyanide interrupt metabolic function?

Answer 8

By inhibition: bonding to complex IX results in a stop of flow of electrons, which in turn causes NADH and FADH2 to accumulate but produces no ATP.

Question 9

Which intermediate of the TCA cycle is involved in the production of amino acids?

Answer 9

a-ketoglutarate (via glutamate hydrogenase), as well as oxaloacetate

Question 10

Which amino acids are anaplerotic?

Answer 10

Isoleucine and valine: convert to propionyl CoA –> succinyl CoA

Question 11

How can fatty acids join the TCA cycle?

Answer 11

Odd-chain fatty acids undergo b-oxidation, producing acetyl coA + propionyl coA. Propinoyl CoA can convert to succinyl coA and join the TCA cycle ( the acetyl coA can combine with oxaloacetate and also join).

Question 12

What is B12 essential for?

Answer 12

Oxidation of odd-chain length fatty acids.

Question 13

What would be an indicator that someone is low in B12?

Answer 13

An accumulation of methylmalonic acid (a sign of pernicious anemia)

Question 14

What is the most important anaplerotic enzyme?

Answer 14

Pyruvate carboxylase, which can generate more oxaloacetate from pyruvate

Question 15

What kind of bonds create the branches in glycogen?

Answer 15

a-1-6-glycosidic bonds

Question 16

What kind of bonds create the backbone of glycogen?

Answer 16

a-1-4-glycosidic bonds

Question 17

Describe the movement of acetyl coA during fatty acid synthesis.

Answer 17

Acetyl coA can’t move out of the mitochondria into the cytoplasm on its own. It combines with oxaloacetate to become citrate. If [ATP] is high, the TCA cycle will slow and citrate will accumulate, leading to citrate diffusing out of the mitochondria. Once in the cytoplasm, it undergoes a reaction to become acetyl coA again (and the oxaloacetate returns to the mitochondria).

Question 18

Describe the regulation of fatty acid oxidation.

Answer 18

Malonyl coA is an intermediate of fatty acid synthesis. It acts as an inhibitor of CPT1, which prevents fatty acyl coA from entering the mitochondria for oxidation.

Question 19

Describe the regulation of fatty acid synthesis.

Answer 19

Acetyl coA carboxylase is the tightly regulated enzyme of interest in fatty acid synthesis.

Insulin causes PP2 to REMOVE phosphate group from acetyl coA carboxylase which ACTIVATES it. Insulin Increases activity.

Glucagon causes AMPPK to phosphorylate acetyl coA carboxylase, which DEactivates it. Glucagon decreases. increased [ATP] will also inhibit activity.

ATP, biotin, and CO2 is necessary for acetyl coA carboxylase to convert acetyl coA –> malonyl coA.

Question 20

When [acetyl coA] is high, how are fatty acids affected?

Answer 20

Thiolase will convert acetyl coa into acetoacetyl coA, which can convert to acetoacetate.

Acetoacetate is a ketone body.

If [NADH] is high in the liver, the acetoacetate will be converted to b-hydroxybutyrate, which will (along with some acetoacetate) will move to circulation.