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BIOC212 > KAZAK 3 > Flashcards

KAZAK 3 Flashcards

1
Q

what reaction does the pyruvate dehydrogenase complex catalyse?

A

pyruvate + CoA + NAD –> acetyl CoA+CO2+NADH

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2
Q

where does the PDC reaction occur?

A

in the mitochondrion

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3
Q

how does pyruvate get inside the mitochondria?

A

through the pyruvate translocase
hydrogen symport (mitochondria pyruvate carrier)
pyruvate is negatively charged, coupled with proton to make a neutral charge when it enters the mitochondria

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4
Q

what is the size of the PDC?

A

9.5 megadaltons

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5
Q

how many coenzymes are required for PDC to work?

A

5

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6
Q

which protein of the PDC complex is where the most regulation happens?

A

E1 - pyruvate dehydrogenase

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7
Q

what are the steps of the PDC reaction?

A
  1. pyruvate is decarboxylated, releases CO2 (irreversible step) by E1
  2. TPP is added to pyruvate to make hydroxyethyl TPP (TPP is regenerated)
  3. hydroxyethyl TPP becomes acetyl-dihyrolipoamine by adding lipoamide (held by disulfide bonds), done by E2
    this reduces the sulfurs
  4. CoA is added to acetyl-dihyrolipoamine, makes acetyl CoA
  5. reduced lipoamine is oxidised by FAD, which itself becomes reduced
  6. FAD is oxidised by NAD, which is itself reduced to NADH
    lipoamide is regenerated
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8
Q

what are the advantages of multi enzyme complexes?

A

minimised distances for substrates in between active sites
increased reaction rate
metabolic intermediates immediately go from active site to active site (side reactions are minimised, protection for chemically dangerous intermediates)
coordinated control of the reactions

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9
Q

which is the enzyme in the PDC that generates the acetyl CoA?

A

E2

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10
Q

what doe Coenzyme A function as

A

functions as a carrier of acetyl and other acyl groups

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11
Q

what are characteristics of Acetyl CoA?

A

acetyl thioester
high energy compound (high energy hydrolysis)
has a high acyl group transfer potential and can donate the acetyl group to several acceptors
entry point of CAC

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12
Q

how is PDC regulated by allostery?

A

NADH and acetyl CoA inhibit the enzyme
product inhibition
prevents useless consumption of pyruvate

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13
Q

what is the difference between allosteric regulations and covalent regulations?

A

allosteric; metabolites pathways communicate to the cell
covalent: regulated by hormones, external cues

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14
Q

how is the PDC regulated by phosphorylation?

A

the active form of E1 (pyruvate dehydrogenase) can be converted to the inactive form by phosphorylation with PDH kinase
it can be reactivated by PDH phosphatase (takes the phosphate off)

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15
Q

what activates and inhibits PDH kinase?

A

activated by ATP, NADH and acetyl CoA
inhibited by pyruvate, ADP

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16
Q

what is the CAC (one sentence)

A

a series of 8 enzymatic reactions that combine acetyl CoA with oxaloacetate to generate CO2, NADH, FADH2 and regenerates the starting product oxaloacetate
generates electron carriers
makes intermediates for biosynthesis

17
Q

what is the yield of the CAC?

A

yields 3 NADH and 2 FADH

18
Q

what does amphibolic mean?

A

site of anabolism and catabolism

19
Q

what type of reactions does anabolism promote? (or is it vice versa)

A

CAC intermediates are used to make more complex molecules
promotes cataplerotic reactions (depletes the intermediates, uses them up)

20
Q

what type of reactions does catabolism promote? (or is it vice versa)

A

CAC intermediates are the end point of the catabolic pathways
anaplerotic reactions: replenish the depleted CAC intermediates

21
Q

what is the overall reaction of the CAC?

A

3NAD+FAD+GDP+Pi+acetyl CoA–>3NADH+FADH2+GTP+CoA+2CO2

22
Q

what is the first reaction of teh CAC

A

acetyl CoA and oxaloacetate are combined by citrate synthase to make citrate

23
Q

which is the reaction that creates a high energy bond?

A

succinyl-CoA is converted to succinate by syccinyl CoA synthetase

24
Q

how many reactions in the CAC have negative delta Gs?

A

three

25
Q

how many ATPs are generated per pyruvate by the CAC?

A

10 ATPs
20 ATPs per glucose

26
Q

how many ATPs does one NADH produce?

A

2.5

27
Q

how many ATPs does one FADH2 produce?

A

1.5

28
Q

how many ATPs does one GTP produce?

A

1

29
Q

what is the CAC flux responsive to?

A

responsive to the energy state of the cell trough allosteric activation
redox state of the cell through the mitochondrial NADH/NAD ratio
availability of energy rich compounds

30
Q

in general what are inhibitors and what are activators

A

activators build up upstream
inhibitors are metabolites that would build up if things stopped

31
Q

what is the total ATP yield of glycolysis + PDC + CAC?

A

glycolysis= 7ATP
PDC= 5ATP
CAC=20 ATM

total 32 ATP/glucose produced

32
Q
A

BIOC212 (32 decks)

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