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Y1 - MCD > Metabolism 4 > Flashcards

Metabolism 4 Flashcards

1
Q

Where does the Krebs cycle take place?

A

Mitochondrial matrix in the presence of oxygen.

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2
Q

Why is oxygen needed for the Krebs cycle to take place?

A

NAD+ and FAD are only regenerated in the presence of oxygen.

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3
Q

What does GTP stand for?

A

Gaunosine triphosphate

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4
Q

Where are the enzymes needed for the Krebs cycle found?

A

Most in the mitochondrial matrix apart from succinate dehydrogenase which is firmly attached to the inner surface do the mitochondrial membrane to directly interact with ubiquinone.

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5
Q

What does GTP do?

A

Can be used as an energy source for protein synthesis and energy transfer in a cell. Involved in signal transduction and regulator of small GTP binding proteins. Similar structure to ATP.

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6
Q

What is amino acid degradation?

A

Removal of the amine group from an amino acid, which is excreted in the urea whilst the carbon back bone is used in respiration.

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7
Q

What is transamination?

A

Reaction in which an amine group is transferred to a keto acid (amino acid without an amine group) so that a new amino acid and new keto acid are produced.

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8
Q

What is produced from the Krebs cycle (one cycle)?

A

2x CO2
3x NADH
1x GTP
1x FADH2

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9
Q

What is the first step of the Krebs cycle?

A

Acetyl group is added to oxaloacetate to form citrate, using the enzyme citrate synthase.

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10
Q

What is the second step of the Krebs cycle?

A

Citrate is dehydrated to cis-acotinate by the enzyme acotinate.

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11
Q

What is the third step of the Krebs cycle?

A

cis-acotinate is dehydrated again to form isocitrate by the enzyme acotinate.

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12
Q

What is the fourth step of the Krebs cycle?

A

Isocitrate is decarboxylated and NADP is reduced to NADPH by the enzyme isocitrate dehydrogenase to form a-ketoglutarate.

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13
Q

What is the fifth step of the Krebs cycle?

A

a-ketoglutarate is decarboxylated and NAD+ is reduced to NADH once again by a-ketoglutarate dehydrogenase to form succinyl-CoA.

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14
Q

What is the sixth step of the Krebs cycle?

A

Succinyl-CoA loses the CoA group to form succinate catalysed by succinyl-CoA synthetase. Meanwhile substrate level phosphorylation produced 1x ATP.

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15
Q

What is the seventh step of the Krebs cycle?

A

Succinate forms fumarate via succinate dehydrogenase. FAD is reduced to FAD2 in the process.

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16
Q

What is the eighth step of the Krebs cycle?

A

Fumarate is hydrated to form malate, using enzyme fumarace.

17
Q

What is the final step of the Krebs cycle?

A

Malate forms oxaloacetate ready for the next cycle. In the process NAD+ is reduced to NADH.

18
Q

What are the two mechanisms for NADH transportation into the mitochondria?

A
  • Glycerol-phosphate shuttle

- Malate-aspartate shuttle

19
Q

How does the glycerol-phosphate shuttle work?

A
  • Cytosolic glycerol-3-phosphate dehydrogenase donates electrons from NADH to dihydroxyacetone phosphate in order to form glycerol-3-phosphate.
  • Membrane-bound (mitochondrial) glycerol-3-phosphate dehydrogenase then donates these electrons to FAD.
  • FAD is linked to Co-enzymes Q (ubiquinone) and passes on the electrons, entering the ETC.
20
Q

Where is the glycerol-phosphate shuttle found?

A

Skeletal muscle and brain

21
Q

Where is the malate-aspartate shuttle found?

A

Liver, kidney and heart.

22
Q

How does the malate-aspartate shuttle work?

A
  • A hydride ion is donated to oxaloacetate from NADH to give malate, catalysed by cytosolic malate dehydrogenase.
  • Malate is transported via an antiporter with a-ketoglutarate into the mitochondria where it is oxidised by, giving oxaloacetate and NADH once again (catalysed by mitochondrial malate dehydrogenase).
23
Q

How many ATP molecules is produced through the oxidation of NADH?

A

3

24
Q

How many ATP molecules is produced through the oxidation of FAD?

A

2

25
Q

How many ATP molecules does the Krebs cycle make per cycle?

A

12 (1x GTP, 3x NADH, 1x FAD)

26
Q

What does NADPH stand for?

A

Nicotinamide adenine dinucleotide phosphate

27
Q

What does NADPH do?

A
  • Relative of NADH with an additional phosphate group
  • Can pick up two high energy electrons and one proton, holding them in high-energy linkage
  • Phosphate gives a different conformation so that enzymes bind differently to NADPH than to NADH
28
Q

What is the Warburg effect?

A

The preferential generation of lactate from glucose even in the presence of oxygen.

Y1 - MCD (38 decks)

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