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BGM1002-Biochemistry > BGM1002/L22 Citric Acid Cycle > Flashcards

BGM1002/L22 Citric Acid Cycle Flashcards

1
Q

Why are metabolic pathways tightly regulated? (4)

A

To link supply with demand
To allow cells to respond to environmental change
To maintain a constant internal environment
To enable different tissues to interact

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2
Q

Give 4 ways in which glycolysis is controlled.

A

Rate-limiting enzymes
Enzymes at start or branch in pathways
Conformational change
Covalent modification
Compartmentalisation of enzymes/substrates

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3
Q

Give an example of conformational change in glycolysis regulation.

A

Allosteric control - non-covalent binding/release of effector molecule

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4
Q

Give an example of covalent modification of enzymes.

A

Phosphorylation of kinase

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5
Q

How would enzymes at the start of a pathway be regulated?

A

Control activity (fast)
Control synthesis (slow)

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6
Q

Where does glycolysis occur?

A

Cytosol

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7
Q

What is the role of adenylate kinase?

A

Turn 2 ADPs into ATP and AMP

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8
Q

Name an allosteric activator for phosphofructokinase.

A

Fructose-2,6-bisphosphate

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9
Q

How does pH affect glycolysis?

A

When acidic intermediates accumulate, pH falls and inhibits glycolysis

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10
Q

Name an inhibitor of phosphofructokinase.

A

Citrate

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11
Q

Where does the citric acid cycle occur?

A

In mitochondria

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12
Q

Give an example of compartmentalisation of substrates.

A

Glucose breakdown can only occur if insulin promotes uptake of glucose by a cell

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13
Q

What enzyme converts pyruvate into Acetyl CoA?

A

Pyruvate dehydrogenase

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14
Q

What is the byproduct of oxidative decarboxylation?

A

CO2

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15
Q

What does pyruvate dehydrogenase require? (2)

A

Dihydrolipoyl transacetylase
Dihydrolipoyl dehydrogenase

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16
Q

What vitamins are required for the citric acid cycle? (3)

A

B1
Riboflavin
Niacin

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17
Q

Give 3 symptoms of vitamin B1 deficiency.

A

Loss of appetite
Lassitude
Numbness of limbs and extremities
Atropy

18
Q

Where is thiamine found?

A

Grain husks
Meat

19
Q

Name 2 types of vitamin B1 deficiency.

A

Beri-Beri
Wernicke-Korsakoff encephalopathy

20
Q

Give 3 fates of pyruvate.

A

Citric acid cycle
Converted to fatty acids
Converted to amino acids
Converted to lactate
Converted to ethanol

21
Q

How is pyruvate converted to amino acids?

A

During anabolic growth, amination to non-essential amino acids occurs

22
Q

How is pyruvate converted to lactate?

A

Under anaerobic conditions, NAD+ regenerated
In step 6, NAD+ converts to NADH via lactate dehydrogenase

23
Q

What enzyme converts pyruvate into lactate?

A

Lactate dehydrogenase

24
Q

How is pyruvate converted to ethanol?

A

Under anaerobic conditions to regenerate NAD+

25
Q

What is the purpose of the Krebs cycle?

A

Harvest high-energy electrons from carbon fuels

26
Q

What are the products of one Krebs cycle?

A

3NADH
FADH2
2CO2
GTP

27
Q

Give the intermediates of the Krebs cycle, starting from pyruvate. (7)

A

Pyruvate
Acetyl CoA
Citrate
Isocitrate
A-ketoglutarate
Succinyl CoA
Oxaloacetate

28
Q

Why is the Krebs cycle described as amphibolic?

A

Involves both catabolism and anabolism

29
Q

What are the products of the Krebs cycle from 2 pyruvates?

A

4CO2
6NADH
2FADH2
2GTP

30
Q

What enzyme converts citrate to isocitrate?

A

Aconitase

31
Q

What enzyme converts isocitrate to a-ketoglutarate?

A

Isocitrate dehydrogenase

32
Q

What enzyme converts a-ketoglutarate to succinyl CoA?

A

a-ketoglutarate dehydrogenase complex

33
Q

What enzyme converts succinyl CoA to succinate?

A

Succinyl CoA synthetase

34
Q

What enzyme converts succinate to fumerate?

A

Succinate dehydrogenase

35
Q

What enzyme converts fumarate to malate?

A

Fumarase

36
Q

What enzyme converts malate to oxaloacetate?

A

Malate dehydrogenase

37
Q

What enzyme converts oxaloacetate to citrate?

A

Citrate synthase

38
Q

Give a pneumonic to remember the intermediates of the citric acid cycle.

A

Organic Acid Chemistry Is a Kangaroo Science Subject For Me

39
Q

What enzyme can produce oxaloacetate directly from pyruvate?

A

Pyruvate carboxylase

40
Q

Why is the citric acid cycle described as amphibolic?

A

It contains both catabolic and anabolic reactions

BGM1002-Biochemistry (29 decks)

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