Metabolism

Question 1

What happens in the mitochondria?

Answer 1

ß-oxidation (fatty acid oxidation), acetyl-CoA production, TCA cycle, oxidative phosphorilation, ketogenesis.

Question 2

What happens in the cytosol?

Answer 2

Glycolysis, HMP shunt, synthesis of cholesterol (SER), proteins (ribosomes, RER), fatty acids and nucleotides.

Question 3

What does a carboxylase do?

Answer 3

It transfers a CO2 group with help of biotin.

Question 4

What does a mutase do?

Answer 4

It relocates a group within a molecule.

Question 5

Which are the enzyme and regulators of Glycolysis?

Answer 5

Enzyme: Phosphofructokinase-1 (PFK-1)

Regulators: AMP +, fructose-2,6-biphosphate +, ATP -, citrate -.

Question 6

Which are the enzyme and regulators of Glycogenesis?

Answer 6

Enzyme: Glycogen synthase

Regulators: G6P +, insulin +, cortisol +, epinephrine -, glucagon -.

Question 7

Which are the enzyme and regulators of the de novo pyrimidine synthesis?

Answer 7

Enzyme: Carbamoyl phosphate synthetase II

Regulators: ATP +, PRPP +, UTP -.

Question 8

Which are the enzyme and regulators of the de novo purine synthesis?

Answer 8

Enzyme: Glutamine-phosphoribosylpyrophosphate (PRPP) amidotransferase.

Regulators: AMP -, IMP -, GMP -.

Question 9

Which are the enzyme and regulators of the urea cycle?

Answer 9

Enzyme: Carbamoyl phosphate synthetase I

Regulators: N-acetylglutamate +

Question 10

Which are the enzyme and regulators of Ketogenesis?

Answer 10

Enzyme: HMG-CoA synthase

Regulators: —

Question 11

Which are the enzyme and regulators of the cholesterol synthesis?

Answer 11

Enzyme: HMG-CoA reductase

Regulators: Insulin +, thyroxine +, estrogen +, glucagon -, cholesterol -.

Question 12

What do mitochondria and cytosol do both in common?

Answer 12

Heme synthesis, Urea cycle, Gluconeogenesis.

HUGs take TWO.

Question 13

What does a dehydrogenase do?

Answer 13

It catalyzes oxidation-reduction reactions.

Question 14

Which are the enzyme and regulators of the TCA cycle?

Answer 14

Enzyme: Isocitrate dehydrogenase.

Regulators: ADP +, ATP -, NADH -.

Question 15

Which are the enzyme and regulators of the fatty acid synthesis?

Answer 15

Enzyme: Acetyl-CoA carboxylase (ACC)

Regulators: Insulin +, citrate +, glucagon -, palmitoyl-CoA -

Question 16

How does ATP production happen?

Answer 16

The aerobic metabolism of a single glucose produces 32 ATP via malate-aspartate shuttle in heart and liver, 30 via glycerol-3-phosphate shuttle in muscle.
The anaerobic glycolysis produces 2 ATP per glucose.
The ATP hydrolysis can be coupled to energetically unfavorable reactions.
Arsenic causes glycolysis to 0 ATP.

Question 17

What are activated carriers? What activated forms do they carry?

Answer 17

• ATP (Phosphoryl groups)
• NADH, NADPH, FADH2 (electrons)
• CoA, lipoamide (acyl groups)
• Biotin (CO2)
• Tetrahydrofolates (l-carbon unites)
• S-adenosylmethionine (SAM) (CH3 groups)
• TPP (aldehydes)

Question 18

Which are the universal electron acceptors?

Answer 18

Nicotinamides (NAD, NADP from vit B3) and flavin nucleotides (FAD from vit B2).

NAD used in catabolic to carry reducing equivalents as NADH.

NADPH in anabolic as supply of reducing equivalents.
It’s product of HMP shunt and used in anabolic processes, respiratory burst, P450 system, glutathione reductase.

Question 19

What are the differences between hexo and gluco kinase?

Answer 19

Phosphorylation of glucose to G6P is catalyzed by gLucokinase in Liver where it stores glucose when high [glucose], hexo catalyzes in other organs where is used even when low [gluc].

Gluco: low affinity, higher Km, Higher Vmax, higher capacity, induced by insulin, feedback is inhibited by G6P.

Hexo: higher affinity, low Km, capacity and Vmax, not induced by insulin and inhibited by +feedback G6P.

Question 20

Which are the key enzymes of the glycolysis regulation?

Answer 20

Glucose + 2 Pi + 2 ADP + 2 NAD&raquo_space; 2 pyruvate + 2 ATP + 2 NADH + 2 H + 2 H2O.
Balance depends in ionization state of reactants and products.

Question 21

What are the differences between hexo and gluco kinase?

Answer 21

Phosphorylation of glucose to G6P is catalyzed by gLucokinase in Liver and ß cells of pancreas where it stores glucose when high [glucose], hexo catalyzes in other organs where is used even when low [gluc].

Gluco: low affinity, higher Km, Higher Vmax, higher capacity, induced by insulin, feedback is inhibited by G6P.

Hexo: higher affinity, low Km, capacity and Vmax, not induced by insulin and inhibited by +feedback G6P.

Question 22

How is the net glycolysis in the cytoplasm?

Answer 22

Glucose + 2 Pi + 2 ADP + 2 NAD&raquo_space; 2 pyruvate + 2 ATP + 2 NADH + 2 H + 2 H2O.
Balance depends in ionization state of reactants and products.

Question 23

Which are the key enzymes of the glycolysis regulation?

Answer 23

Requiere ATP:

Glucose -hexo/glucokinase -> G6P

G6P (neg) hexokinase
F6P (neg) glucokinase

F6P - Phosphofructokinase 1 (rate-limiting step) -> F1,6-BP

AMP +, F-2,6-BP+.
ATP-, citrate -.

Produce ATP:

1,3-BPG < phosphoglycerate kinase > 3-PG

Phosphoenolpyruvate - pyruvate kinase -> pyruvate.

Fructose-1,6-bisphosphate+.
ATP-, alanine-.