Chapter 18: Preparation for the Cycle Flashcards Preview

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Flashcards in Chapter 18: Preparation for the Cycle Deck (37):
1

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

Aerobic conditions

Acetyl CoA

2

Acetyl CoA is the fuel for the...

Citric acid cycle

3

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

The mitochondrial matrix

4

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

Cytoplasm to mitochondria

In symport with H+

5

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

Pyruvate to acetyl CoA

6

Pyruvate dehydrogenase complex is ________ and a link between...

Irreversible reaction

Link between glycolysis and the citric acid cycle

7

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

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

 

8

The prosthetic group for E1 is...

TPP

9

The prosthetic group for E2 is...

Lipoamide

10

The prosthetic group for E3 is...

FAD

11

3 steps of PDH are...

  1. Decarboxylation
  2. Oxidation
  3. Transfer to CoA

12

What is the catalyst for the decarboxylation reaction?

E1 or pyruvate dehydrogenase component

*Combines with TPP

13

Step 2 of PDH:

Oxidation of TPP by E1

14

Step 3 of PDH:

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

15

Step 4 of PDH:

Dihydrolipoamide is oxidized back to lipoamide (E3)

16

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

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

17

What happens if lipoamide or TPP are not present?

Pyruvate will not convert to Acetyl CoA

18

Acetyl CoA has two key principle fates:

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

19

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

Glucose

Lipids cannot form glucose from acetyl CoA

20

PDH is regulated by _________ and _________.

Covalent modification and allosteric interactions

21

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

Phosphorylates and inactivates E1

22

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

Removes phosphate

Activates the enzyme

23

PDH also regulated by allosteric reactions, specifically...

Energy charge

24

PDH is inhibited by...

  • ATP
  • Acetyl CoA
  • NADH

25

PDH activated by...

  • ADP
  • Pyruvate

26

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

Phosphorylated; inactive

27

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

Converted to lactate

Leading to lactic acidosis 

Malfunctioning CNS

28

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

Thiamine or vitamin B1

29

With Beriberi, PDH activity is _____ and results in...

Activity is low

Results in pyruvate accumulation.

No conversion to acetyl CoA? This limits ATP production!

30

What causes similar symptoms to those in Beriberi?

Exposure to mercury or arsenite

31

Arsenite and mercury bind to _________ and ______ PDH complex.

Bind to dihydrolipoamide

Inhibit PDH

32

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

Sulfhydryl reagents

33

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

Lewisite

34

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

Lipoamide

35

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

Pyruvate

36

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

Lipoamide; transfer of the acetyl group to CoA.

37

How does the antidote for lewisite work?

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