Lecture 5 - Bioenergetics and TCA cycle?

Question 1

What is the distinction between deltaG* and deltaG?

Answer 1

DeltaG* calculated w/ 1M products and reactant, deltaG at actual concentrations

Question 2

What does a Keq greater than 1 indicate?

Answer 2

Products favored

Question 3

What does a Keq smaller than 1 indicate?

Answer 3

Reactants favored

Question 4

What does a negative deltaG indicate?

Answer 4

Products favored

Question 5

What does a positive deltaG indicate?

Answer 5

Reactants favored

Question 6

Where does beta oxidation occur?

Answer 6

Mitochondrial matrix

Question 7

Where does TCA cycle occur?

Answer 7

Mitochondrial matrix

Question 8

State the enzymes of the TCA starting with the enzyme that acts on Acetyl-CoA.

Answer 8

Citrate synthase > Aconitase > Aconitase > Isocitrate dehydrogenase > alpha-ketoglutarate dehydrogenase > succinyl-CoA synthetase > succinate dehydrogenase > fumarase > malate dehydrogenase
(CS A A ID alphaKD S SD F MD)

Question 9

What regulates isocitrate dehydrogenase?

Answer 9

(+)Ca2+, (+)ADP (allosteric), (-)NADH

Question 10

What regulates alpha-ketoglutarate dehydrogenase complex?

Answer 10

(+)Ca2+, (+)NADH, (-)Succinyl-CoA (product of alpha-ketoglutarate)

Question 11

What regulates malate dehydrogenase?

Answer 11

(-)NADH

Question 12

State the input and outputs into 1 cycle of the TCA loop.

Answer 12

INPUT: 2-carbon unit (Acetyl-CoA)
OUTPUT: 2 CO2, 1GTP, 8 high energy e-

Question 13

What enzyme converts pyruvate to acetyl-coA?

Answer 13

Pyruvate dehydrogenase complex (PDH)

Question 14

How many carbons make up pyruvate?

Answer 14

3

Question 15

How many carbons make up acetyl-coA?

Answer 15

2

Question 16

What are the outputs of the oxidation of pyruvate?

Answer 16

Acetyl-CoA, CO2, NADH (per pyruvate molecule)

Question 17

What is the general enzymatic set-up of the alpha-keto acid family enzymes?

Answer 17

Highly integrated set of three units:

E1 - Thiamine pyrophosphate (TPP), E2 - Lip-S-S, E3 - FAD

Question 18

What is the significance of arsenite relative to alpha-leto acid enzymes?

Answer 18

binds S-S of Lipoate and inactivates enzyme.

Question 19

How is PDH (or PDC) regulated?

Answer 19

Phosphorylation INACTIVATES
Dephosporylation ACTIVATES
Activation: Phosphatase (Ca2+ activated)
Inactivation: Kinase (ADP & Pyruvate inhibit, Ac-CoA & NADH activate)

Question 20

What is added to NAD+ by ID and alpha-KD?

Answer 20

Hydride ion (2 e- and proton)

Question 21

Where does substrate level phosphorylation occur in the TCA cycle?

Answer 21

Succyinyl CoA Synthetase (Succinate thiokinase)

Question 22

Dry beriberi

Answer 22

low B1 + peripheral neuropathy, impaired reflex functions

Question 23

Wet beriberi

Answer 23

low B1 + cardiovascular disease

Question 24

How to chronic alcohol abuse cause thiamine deficiency?

Answer 24

Ethanol inhibits thiamine intake + alcohol abuse often accompanied by poor nutrition

Question 25

What inhibits function of citrate synthase?

Answer 25

Citrate - it's own product, negative feedback

Question 26

How many ATP/cycle?

Answer 26

1 GTP + 3 NADH + 1 FADH2 = 10ATP/cycle

Question 27

Explain why anaplerotic pathways are necessary.

Answer 27

Intermediates in the TCA cycle may be used for biosynthetic reactions and thus deplete a given intermediate. Anaplerotic pathways allows intermediates to be "re-filled" or replenished.

Question 28

List the three anaplerotic pathways contained within the notes.

Answer 28

1) Substrate: pyruvate, Enzyme: pyruvate carboxylase, Intermediate: oxaloacetate 2) Substrate: Glutamate, Enzyme: Glutamate dehydrogenase + transaminase, Intermediate alpha-ketglutarate 3) Substrate: Odd # FAs, valine, & isoleucine > propionyl CoA then enter as intermediate: Succinyl CoA