S6 TCA Cycle And Oxidative Phosphorylation Flashcards Preview

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Flashcards in S6 TCA Cycle And Oxidative Phosphorylation Deck (12)
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1
Q

What two reactions start the TCA cycle?

A
  1. Pyruvate (3C) + CoA to Acetyl CoA (2C)+ CO2 (enzyme: pyruvate dehydrogenase)
  2. Acetyl CoA (2C) + Oxaloacetate (4C) to Citrate (6C) (oxidation of Acetyl CoA)
2
Q

Is citrate a high or low energy molecule?

A

High energy - because it’s produced

3
Q

How many NADH, FADH2 and GTP molecules are produced?

A

6 NADH
2 FADH2
2 GTP

4
Q

What is GTP?

A

Lower energy equivalent of ATP

5
Q

How is the TCA cycle regulated?

A

It is regulated by energy availability (presence/ratio of low and high energy molecules).

Stimulated by: ADP and NAD+
Inhibited by: ATP, NADH and succinyl-CoA

6
Q

How are the ETC and ATP synthesis uncoupled?

A

By uncouplers that increase the permeability of the inner mitochondrial membrane to H+. Means the H+ gradient is reduced (H+ move back through membrane without ATPase) so less/no drive for ATP synthesis.

7
Q

Name two inhibitors of oxidative phosphorylation and how they inhibit.

A
  1. CN-
  2. CO

Inhibit by blocking the ETC.
They mimic O2 so bind to Hb inhibiting the O2 to H2O reaction.

8
Q

Coenzymes in oxidative phosphorylation

A

NADH to NAD+
FADH2 to FAD

Electrons in NADH have more energy than FAD2H

9
Q

What is a PTC?

What is pmf?

A

Proton translocating complex - “pump” H+ into intermembrane space.

Proton motive force - H+ gradient across inner mitochondrial membrane.

10
Q

Oxidative vs substrate level phosphorylation

A

Oxidative: requires membrane-associated complexes, indirect energy coupling, can’t occur without O2, major process for ATP synthesis in cells needing lots of energy.

Substrate level: requires soluble enzymes, direct energy coupling, can occur without O2, minor process for ATP synthesis in cells needing lots of energy

11
Q

What is the link between brown adipose tissue and uncoupling of ETC and ATP synthesis?

A

Brown adipose tissue contains thermogenin (natural uncoupling protein). In response to the cold, noradrenaline activates:

  1. Lipase to release fatty acids from triacylglycerol
  2. Fatty acid is oxidised, produces NADH/FADH2 which are used in the ETC
  3. Fatty acids activate thermogenin
  4. Thermogenin transports H+ back into mitochondria (uncoupling) as H+ gradient reduced
  5. Energy produced by pmf is released as hea
12
Q

Which 5 biosynthetic processes does the TCA cycle supply?

A
  1. Citrate - Fatty acids
  2. Alpha-ketoglutarate - amino acids
  3. Succinate - haem and amino acids
  4. Malate - amino acids
  5. Oxaloacetate - glucose and amino acids

(Amino acid ones are reversible)