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Biochem Test II > Mueller A-CoA and CAC > Flashcards

Mueller A-CoA and CAC Flashcards

1
Q

What is another name for pantothenic acid?

A

vitamin B5

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2
Q

What provides the reactive sulfhydryl for CoA? What amino acid provides for this?

A

Mercaptoethylamine. Cysteine decarboxylation.

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3
Q

The reduced thiol of CoA can react with what to produce what?

A

carbxyl groups to form thioester linkages.

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4
Q

What can CoA accept?

A

acyl groups.

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5
Q

What are two other forms of CoA (other than acetyl) that we will encounter?

A

succinyl CoA

fatty acyl-CoA

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6
Q

What is the major source of pyruvate for the cell?

A

glycolysis

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7
Q

What links the citric acid cycle to glycolysis?

A

formation of acetyl-CoA from pyruvate

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8
Q

What reducing equivalent does the PDH complex produce?

A

NADH

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9
Q

What are the names for the enzymes involved in the PDH complex?

A

pyruvate decarboxylase (ENa)

dihydrolipoyl transacetylase (ENb)

dihydrolipoyl dehydrogenase (ENc)

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10
Q

What is the first reaction catalyzed by the PDH complex?

A

decarboxylation of pyruvate by pyruvate decarboxylase

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11
Q

What is the phosphorylated name of thiamine?

A

thiamine pyrophosphate

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12
Q

Pyruvate decarboxylase requires what cofactor?

A

thiamine pyrophosphate

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13
Q

During the action of pyruvate decarboxylase, what is acetyl group transienstly bound to?

A

TPP

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14
Q

What enzyme accept the acetyl group from ENa?

A

dihydrolipoyl transacetylase.

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15
Q

What enzymatic reaction does dihydrolipoyl transacetylase carry out?

A

forms acetyl-CoA

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16
Q

What is the by-product of the dihydropipoyl transacetylase reaction?

A

TPP-ENa

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17
Q

What is the co-enzyme subunit for dihydrolipoyl transacetylase (ENb)?

A

lipoamide

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18
Q

What are the two steps in the reaction carried out by dihydrolipoyl transacetylase?

A
  1. one sulfur from lipoamide accepts the 2C from TPP-ENa and the other sulfur is reduced
  2. the acetyl group is transferred to CoA and the other (now both) sulfur is reduced
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19
Q

What is the purpose of dihydrolipoyl dehydrogenase?

A

regenerates the active (fully oxidized) form of lipoamide

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20
Q

What reducing equivalent is created by the action of dihydrolipoyl dehydrogenase?

A

FADH2

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21
Q

How many steps are in involved in the action of dihydrolipoyl dehydrogenase? What are they?

A
  1. both hydrogen atoms from lipoamide are transferred to FAD to generate FADH2
  2. FADH2 is reoxidized to form NADH and H+
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22
Q

What is the fate of FADH2 in this reaction of dihydrolipoyl dehydrogenase?

A

nothing. it is simply a reaction intermediate.

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23
Q

Where is the PDH complex found?

A

mitochondrial matrix

24
Q

Where is pyruvate generated?

A

in the cytosol (from glycolysis)

25
Q

How does pyruvate make its way to the mitochondrial matrix?

A

Translocase

26
Q

Where is translocase located?

A

The inner mitochondrial membrane.

27
Q

What product will accumulate by inhibition of the PDH complex?

A

pyruvate.

28
Q

What will happen to this excess pyruvate?

A

It will be converted to lactate by lactate dehydrogense

29
Q

What will be seen systemically in this process?

A

serum lactic acidemia

30
Q

What B vitamin makes up NADH?

A

niacin, vitamin B3

31
Q

What vitamin makes up FAD/FADH2?

A

riboflavin (B2)

32
Q

How many reducing equivalents does one turn of the CAC produce?

A

3 ATP and 1 FADH2

33
Q

How many ATPs can NADH yield?

A

3

34
Q

How many ATPs can FADH2 yield?

A

2

35
Q

Can the CAC function in the absence of oxygen?

A

No.

36
Q

What metabolic process will proceed in the absence of O2?

A

pyruvate will be oxidized to lactate using NADH

37
Q

What are the two main roles of the CAC?

A
  1. major ATP generating pathway in most aerobic cells

2. source of biosynthetic intermediates

38
Q

What reaction is catalyzed by pyruvate carboxylase?

A

conversion of pyruvate, ATP and HCO3 into OAA

39
Q

What substance allosterically activates pyruvate carboxylase?

A

acetyl-CoA

40
Q

What co-factor is required for the activity of pyruvate carboxylase?

A

Biotin

41
Q

What reaction does glutamate dehydrogenase catalye?

A

coversion of glutamate to alpha-ketoglutarate

42
Q

What three products would signal a high energy state of the cell?

A

acetyl-CoA

citrate (and other CAC intermediates)

NADH

43
Q

What products decrese the activity of the PDH?

A

acetyl-CoA, citrate, NADH

44
Q

What two products allosterically inhibit the activity of PDH?

A

Acetyl-CoA and NADH

45
Q

indirectly, what two other products can inhibit the PDH?

A

fatty acids and ATP

46
Q

How does the phosphorylation state affect the PDH?

A

phosphorylated PDH = less active

de-phosphorylated PDH = more active

47
Q

What two enzymes control the phosphorylation state of the PDH?

A

PDH kinases and PDH phosphatases

48
Q

What two products activate PDH kinase?

A

acetyl-CoA and NADH

49
Q

What four products inhibit the activity of the kinase? What affect will be seen because of this?

A

NAD+, CoA-SH, ADP, pyruvate

50
Q

What two enzymes of the CAC are regulated?

A

isocitrate dehydrogenase and aKG dehydrogenase

51
Q

What product activates isocitrate dehydrogenase?

What product inhibits isocitrate dehydrogenase?

A

ADP.

NADH.

52
Q

What two products inhibit the activity of aKG Dehydrogenase?

A

NADH and succinyl-CoA

53
Q

What enzyme is often implicated in chronic lactic acidosis in infants and children?

A

any subunit of the PDH

54
Q

What vitamin is absent in patients suffering from Wernicke Korsakoff syndrome?

A

thiamine

55
Q

beri-beri

A

severe dietary deficiency of thiamine

56
Q

What are the two most important inhibitors of PDH activity?

A

NADH and acetyl-CoA

57
Q

What are the two most regulated enzymes of the CAC?

A

isocitrate dehydrogenase and alpha-KG dehydrogenase

Biochem Test II (14 decks)

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