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Biochemistry Exam 2 > Chapter 18: Preparation for the Cycle > Flashcards

Chapter 18: Preparation for the Cycle Flashcards

1
Q

Under _____ conditions, pyruvate enters the mitochondria and is converted to ________.

A

Aerobic conditions

Acetyl CoA

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2
Q

Acetyl CoA is the fuel for the…

A

Citric acid cycle

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3
Q

Oxidative decarboxylation of pyruvate and the reactions of the citric acid cycle occur within…

A

The mitochondrial matrix

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4
Q

Pyruvate translocase transports the pyruvate produced during glycolysis in the _______ into __________ in ____________.

A

Cytoplasm to mitochondria

In symport with H+

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5
Q

Pyruvate dehydrogenase complex catalyzes the oxidative phosphorylation of _______ to _______.

A

Pyruvate to acetyl CoA

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6
Q

Pyruvate dehydrogenase complex is ________ and a link between…

A

Irreversible reaction

Link between glycolysis and the citric acid cycle

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7
Q

PDH requires 3 enzymes to synthesize acetyl CoA. What are they?

A
  1. Pyruvate dehydrogenase component (E1)
  2. Dihydrolipoyl transacetylase (E2)
  3. Dihydrolipoyl dehydrogenase (E3)
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8
Q

The prosthetic group for E1 is…

A

TPP

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9
Q

The prosthetic group for E2 is…

A

Lipoamide

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10
Q

The prosthetic group for E3 is…

A

FAD

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11
Q

3 steps of PDH are…

A
  1. Decarboxylation
  2. Oxidation
  3. Transfer to CoA
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12
Q

What is the catalyst for the decarboxylation reaction?

A

E1 or pyruvate dehydrogenase component

*Combines with TPP

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13
Q

Step 2 of PDH:

A

Oxidation of TPP by E1

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14
Q

Step 3 of PDH:

A

Formation of acetyl CoA (E2) + dihydrolipoamide (reduced form)

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15
Q

Step 4 of PDH:

A

Dihydrolipoamide is oxidized back to lipoamide (E3)

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16
Q

What two conditions must be present for the coordinated catalysis of this reaction?

A
  1. Flexible lipoamide arm
  2. Structural integration of the 3 enzymes (must be tightly associated)
17
Q

What happens if lipoamide or TPP are not present?

A

Pyruvate will not convert to Acetyl CoA

18
Q

Acetyl CoA has two key principle fates:

A
  1. Metabolism by the citric acid cycle
  2. Incorporation into fatty acids
19
Q

Because it is an irreversible reaction, acetyl CoA cannot convert back to ______ and therefore _____ cannot be used to make _____.

A

Glucose

Lipids cannot form glucose from acetyl CoA

20
Q

PDH is regulated by _________ and _________.

A

Covalent modification and allosteric interactions

21
Q

A kinase associated with the complex __________ and __________ E1 subunit of PDH.

A

Phosphorylates and inactivates E1

22
Q

A phosphatase associated with the complex removes the _______ and thereby _______ the enzyme.

A

Removes phosphate

Activates the enzyme

23
Q

PDH also regulated by allosteric reactions, specifically…

A

Energy charge

24
Q

PDH is inhibited by…

A
  • ATP
  • Acetyl CoA
  • NADH
25
Q

PDH activated by…

A
  • ADP
  • Pyruvate
26
Q

If there is a phosphotase deficiency, PDH is always ________ and therefore ______.

A

Phosphorylated; inactive

27
Q

When inactive, PDH is converted to ______ leading to __________ and malfunctioning the ____________.

A

Converted to lactate

Leading to **lactic acidosis **

Malfunctioning CNS

28
Q

Beriberi: A neurological and cardiovascular disorder caused by dietary deficiency of _______ or ______.

A

Thiamine or vitamin B1

29
Q

With Beriberi, PDH activity is _____ and results in…

A

Activity is low

Results in pyruvate accumulation.

No conversion to acetyl CoA? This limits ATP production!

30
Q

What causes similar symptoms to those in Beriberi?

A

Exposure to mercury or arsenite

31
Q

Arsenite and mercury bind to _________ and ______ PDH complex.

A

Bind to dihydrolipoamide

Inhibit PDH

32
Q

What relieves the inhibition of PDH by forming a complex with arsenite?

A

Sulfhydryl reagents

33
Q

What is the arsenic-based chemical weapon used in WWI?

A

Lewisite

34
Q

The prosthetic group _____________ is required for the transfer of the acetyl group to coenzyme A.

A

Lipoamide

35
Q

The Pyruvate Dehydrogenase (PDH) Complex is allosterically activated by high levels of:

A

Pyruvate

36
Q

The E2 enzyme (dihydrolipolyl transacetylase) of the pyruvate dehydrogenase complex contains _______________ as prosthetic group and catalyzes the___________________.

A

Lipoamide; transfer of the acetyl group to CoA.

37
Q

How does the antidote for lewisite work?

A

BAL: Sulfhydryl reagent 2,3-dimercaptopropanol reacts arsenite and is then excreted

Biochemistry Exam 2 (10 decks)

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