Acetyl CoA And Citric Cycle Flashcards

1
Q

Where is pyruvate transferred to in aerobic respiration and why

A

Mitochondria to be converted into acetyl coA

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2
Q

Which enzyme removed/ oxidises pyruvate of H+

A

Pyruvate dehydrogenase

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3
Q

What is pyruvate dehydrogenase part of

A

A multi enzyme complex with other enzymes involved

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4
Q

Apart from dehydrogenase removing oxidating pyruvate what happens

A

Decarboxylation

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5
Q

Which vitamins are needed to convert pyruvate to acetyl coa

A

B1- thiamine pyrophosphate

Riboflavin- FAD

Niacin- NAD

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6
Q

Explain the process of reducing pyruvate using the 3 cofactor vitamins aswell as pyruvate dehydrogenase

A

Thiamine pyrophosphate removes H from pyruvate to produce thiamine

This then passes it to FAD to be reduced into FADH2

This then allows reduction by passing of H to nad to produce NADH2

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7
Q

Apart from the pyruvate conversion to acetyl coa , what other fates does it have

A

1- pyruvate can be turned into fatty acids to then be stored as triglycerides storage for energy

2- can be turned into amino acids for anabolic growth

3- anaerobic respiration into lactate

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8
Q

How is pyruvate converted to amino acids

A

Addition of amine groups

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9
Q

How is pyruvate converted into lactate to regenerate NAD in anaerobic respiration

A

NADH is oxidised and 2H is used to reduce pyruvate producing lactate

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10
Q

What happens when lactate is produced , how can it be converted back if 02 is present

A

Lactate dehydrogenase removed H and converts it back into pyruvate

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11
Q

What occurs in yeast when pyruvate is reduced by NADH into NAD?

A

It produces ethanol

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12
Q

What is the net gain from pyruvate dehydrogenase process (2 cycles)

A

2 x acetyl coa

2 co2

2 NADH

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13
Q

What is the main importance of the citric acid cycle/ Krebs cycle

A

Forms reducing power (NADH and FADH)

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14
Q

What type of reaction occurs that joins oxaloacetate (4C) with acetyl coA (2C)

A

Condensation reaction

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15
Q

Which enzyme catalyses the condensation of oxaloacetate with acetyl coA into citrate

A

Citrate synthase (6C)

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16
Q

What happens to citrate 6C when produced by condensation citrate synthase

A

Rearrangement occurs

Citrate into isocitrate (isomer of citrate)

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17
Q

How is citrate rearranged into isocitrate (which enzyme)

A

Aconitase enzyme

18
Q

What happens to isocitrate to be converted into a- ketoglutarate

A

Gets oxidised by isocitrate dehydrogenase which converts NAD into NADH

Also gets decarboxylated

19
Q

What is it called when eg isocitrate gets both dehydroxylated by isocitrate dehydrogenase and decarboxylated removing co2

A

Oxidative decarboxylation (occurs to pyruvate aswell)

20
Q

What happens to a-ketoglutarate (5C) when produced from isocitrate dehydrogenase

A

Oxidative decarboxylation again (forming NADH and co2)

This forms succinyl coA (thioester bond)

21
Q

Which enzyme oxidative decarboxylates a keto glutarate

A

A ketoglutarate dehydrogenase

22
Q

How is succinyl coA formed (4C)

A

CoA is added to form thioester with a ketoglutarate produced by isocitrate dehydrogenase

CoA -S- forms a thioester with a ketoglutarate

23
Q

What happens when the thioester bond on succinyl coA is hydrolysed

A

Used to generate GTP from GDP + pi

Energy production

24
Q

What happens when the succinyl coA thioester is hydrolysed

A

Succinyl coA synthetase regenerates a succinate molecule (4C)

25
Q

How is succinate converted into fumarate (4C)

A

Succinate dehydrogenase reduces FAD into FADH oxidising succinate into fumarate

26
Q

What happens when fumarate is produced

A

Converted into malate by fumarase enzyme

Adds H2O molecule (hydration)

27
Q

Where in the Krebs cycle does hydration h20 happen

A

Fumarate into malate

28
Q

How is malate converted into oxaloacetate

A

Malate dehydrogenase reduces NAD into NADH

29
Q

What is the net gain of Molecules in 2 Krebs cycles

A

6 NADH

2 FADH

4 co2

2 GTP

30
Q

Why is citric cycle called amphibollic

A

Both used for anabolic purposes and catabolic

31
Q

What is oxaloacetate used to generate in anabolic reactions

A

Aspartate which can produce amino acids or purines like atp

32
Q

What can citrate be used to generate

A

Fatty acids for storage etc

33
Q

What can a ketoglutarate be used to produce

A

Glutamate into amino acids

34
Q

What is succinyl coa importent for

A

Porphyrin and heme in RBCs

35
Q

Which 3 enzymes in citric acid cycle are controlled

A

Pyruvate dehydrogenase

Isocitrate dehydrogenase

A ketoglutarate dehydrogenase

36
Q

When is pyruvate dehydrogenase activated and inactivated

A

Active when- ADP present, a lot of pyruvate

Inactive when - a lot of acetyl coa or atp or NADH present

37
Q

When is isocitrate dehydrogenase activated and inactive

A

Activated when - a lot of ADP which needs to be produced into ATP

Inactive when - too much ATP or NADH present

38
Q

When is a ketoglutarate dehydrogenase active and inactive

A

Active when - ADP present (low energy),

Inactive when - too much coa , succinyl , atp or dehydrogenase

39
Q

How is acetyl coA turned into fat storage for energy

A

Converted to fatty acids then into triglycerides with the help of citrate

40
Q

Why can triglycerides be used for energy storage

A

Because when broken down (oxidised) the fatty acids can be converted back into acetyl coA for the citric acid cycle