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
How is succinate converted into fumarate (4C)
Succinate dehydrogenase reduces FAD into FADH oxidising succinate into fumarate
26
What happens when fumarate is produced
Converted into malate by fumarase enzyme Adds H2O molecule (hydration)
27
Where in the Krebs cycle does hydration h20 happen
Fumarate into malate
28
How is malate converted into oxaloacetate
Malate dehydrogenase reduces NAD into NADH
29
What is the net gain of Molecules in 2 Krebs cycles
6 NADH 2 FADH 4 co2 2 GTP
30
Why is citric cycle called amphibollic
Both used for anabolic purposes and catabolic
31
What is oxaloacetate used to generate in anabolic reactions
Aspartate which can produce amino acids or purines like atp
32
What can citrate be used to generate
Fatty acids for storage etc
33
What can a ketoglutarate be used to produce
Glutamate into amino acids
34
What is succinyl coa importent for
Porphyrin and heme in RBCs
35
Which 3 enzymes in citric acid cycle are controlled
Pyruvate dehydrogenase Isocitrate dehydrogenase A ketoglutarate dehydrogenase
36
When is pyruvate dehydrogenase activated and inactivated
Active when- ADP present, a lot of pyruvate Inactive when - a lot of acetyl coa or atp or NADH present
37
When is isocitrate dehydrogenase activated and inactive
Activated when - a lot of ADP which needs to be produced into ATP Inactive when - too much ATP or NADH present
38
When is a ketoglutarate dehydrogenase active and inactive
Active when - ADP present (low energy), Inactive when - too much coa , succinyl , atp or dehydrogenase
39
How is acetyl coA turned into fat storage for energy
Converted to fatty acids then into triglycerides with the help of citrate
40
Why can triglycerides be used for energy storage
Because when broken down (oxidised) the fatty acids can be converted back into acetyl coA for the citric acid cycle