Lectures 7-12

Question 1

What does the citric acid cycle do, overall?

Answer 1

converts Acetyl-CoA to CO2

Question 2

where does the CAC take place?

Answer 2

mitochondria

Question 3

What is acetyl-CoA formed from?

Answer 3

carbs, FAs, ethanol, some AAs

Question 4

What is the outcome via the CAC from one Acetyl CoA?

Answer 4

3 NADH, 1 FADH2, 2 CO2, 1 GTP

Question 5

Does the CAC require O2?

Answer 5

YES

Question 6

what is the key regulatory enzyme in the CAC?

Answer 6

isocitrate dehydrogenase

Question 7

what inhibits/activates isocitrate dehydrogenase?

Answer 7

inhibits: ATP, NADH.
Activates: ADP

Question 8

if isocitrate dehydrogenase is inhibited, what happens?

Answer 8

carbon from citric acid is diverted to fatty acids

Question 9

what else are metabolized in the CAC?

Answer 9

acetoacetate, ethanol

Question 10

Can acetyl CoA be used for the net synthesis of glucose?

Answer 10

no

Question 11

what are anaplerotic reactions?

Answer 11

replenish metabolites of the CAC

Question 12

where is acetoacetate created? from what starting materials?

Answer 12

created in liver from fatty acids. exported to bloodstream

Question 13

what can brain use as fuel (2 things)?`

Answer 13

glucose, acetoacetate (during starvation, diabetes)

Question 14

ethanol is metabolised where, and to what?

Answer 14

in liver, to acetyl-CoA

Question 15

what are 2 enzymes used to metabolize ethanol?

Answer 15

1. alcohol dehydrogenase (ADH)

2. acetaldehyde dehydrogenase (ALDH)

Question 16

what is produced when ethanol is metabolized to acetyl-CoA?

Answer 16

2 NADH

Question 17

what can result from excessive alcohol consumption?

Answer 17

acetaldehyde congregation in liver (toxic, damaging)

Question 18

what does antabuse do?

Answer 18

blocks function of acetaldehyde dehydrogenase

Question 19

what causes alcohol intolerance?

Answer 19

mutation in acetaldehyde dehydrogenase

Question 20

what does alcohol metabolism do to the NADH:NAD ratio?

Answer 20

increases NADH level in hepatocytes

Question 21

entry of carbon into the CAC controlled by what?

Answer 21

pyruvate dehydrogenase and citrate synthase

Question 22

where is lactate converted into pyruvate?

Answer 22

cytoplasm (enzyme = LDH)

Question 23

where is pyruvate converted into Acetyl CoA?

Answer 23

in mitochondria (by PDH)

Question 24

how does pyruvate enter the mitochondria?

Answer 24

facilitated diffusion/via membrane transporter

Question 25

what happens to NADH and FADH2 after being created by CAC?

Answer 25

oxidized by mitochondria to form ATP

Question 26

how many carbons are lost during one CAC?

Answer 26

2, in the form of CO2

Question 27

what is the first irreversible reaction in the CAC?

Answer 27

isocitrate dehydrogenase (isocitrate to alpha-ketoglutarate)

Question 28

There are 3 irreversible enzymes in the CAC: what are they?

Answer 28

Citrate synthase, isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase

Question 29

what effect will high NADH have on lactate oxidation?

Answer 29

will inhibit it because lactate -> pyruvate requires NAD and produces NADH

Question 30

why is ethanol especially fattening?

Answer 30

ethanol makes 2 NADH as it is converted to acetyl CoA, which diminishes the need to oxidize fat, and puts carbon in the CAC while bypassing the pyruvate dehydrogenase reaction which controls entry of carbon into the CAC