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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
How does pyruvate make its way to the mitochondrial matrix?
Translocase
26
Where is translocase located?
The inner mitochondrial membrane.
27
What product will accumulate by inhibition of the PDH complex?
pyruvate.
28
What will happen to this excess pyruvate?
It will be converted to lactate by lactate dehydrogense
29
What will be seen systemically in this process?
serum lactic acidemia
30
What B vitamin makes up NADH?
niacin, vitamin B3
31
What vitamin makes up FAD/FADH2?
riboflavin (B2)
32
How many reducing equivalents does one turn of the CAC produce?
3 ATP and 1 FADH2
33
How many ATPs can NADH yield?
3
34
How many ATPs can FADH2 yield?
2
35
Can the CAC function in the absence of oxygen?
No.
36
What metabolic process will proceed in the absence of O2?
pyruvate will be oxidized to lactate using NADH
37
What are the two main roles of the CAC?
1. major ATP generating pathway in most aerobic cells | 2. source of biosynthetic intermediates
38
What reaction is catalyzed by pyruvate carboxylase?
conversion of pyruvate, ATP and HCO3 into OAA
39
What substance allosterically activates pyruvate carboxylase?
acetyl-CoA
40
What co-factor is required for the activity of pyruvate carboxylase?
Biotin
41
What reaction does glutamate dehydrogenase catalye?
coversion of glutamate to alpha-ketoglutarate
42
What three products would signal a high energy state of the cell?
acetyl-CoA citrate (and other CAC intermediates) NADH
43
What products decrese the activity of the PDH?
acetyl-CoA, citrate, NADH
44
What two products allosterically inhibit the activity of PDH?
Acetyl-CoA and NADH
45
indirectly, what two other products can inhibit the PDH?
fatty acids and ATP
46
How does the phosphorylation state affect the PDH?
phosphorylated PDH = less active de-phosphorylated PDH = more active
47
What two enzymes control the phosphorylation state of the PDH?
PDH kinases and PDH phosphatases
48
What two products activate PDH kinase?
acetyl-CoA and NADH
49
What four products inhibit the activity of the kinase? What affect will be seen because of this?
NAD+, CoA-SH, ADP, pyruvate
50
What two enzymes of the CAC are regulated?
isocitrate dehydrogenase and aKG dehydrogenase
51
What product activates isocitrate dehydrogenase? What product inhibits isocitrate dehydrogenase?
ADP. NADH.
52
What two products inhibit the activity of aKG Dehydrogenase?
NADH and succinyl-CoA
53
What enzyme is often implicated in chronic lactic acidosis in infants and children?
any subunit of the PDH
54
What vitamin is absent in patients suffering from Wernicke Korsakoff syndrome?
thiamine
55
beri-beri
severe dietary deficiency of thiamine
56
What are the two most important inhibitors of PDH activity?
NADH and acetyl-CoA
57
What are the two most regulated enzymes of the CAC?
isocitrate dehydrogenase and alpha-KG dehydrogenase

Biochem Test II (14 decks)

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