Lecture 3

Question 1

What determines the fates of pyruvate?

Answer 1

availability of oxygen

Question 2

true of false; fermentation allows glycolysis to proceed in the absence of oxygen?

Answer 2

true

Question 3

Where does pyruvate go if oxygen is present?

Answer 3

mitochondria where is converted to acetyl coa by pyruvate dehydrogenase

Question 4

When is the route of pyruvate to the mitochondria most favoured?

Answer 4

elevated levels of acetyl CoA in the mitochondria

Question 5

What is fate 1

Answer 5

the conversion of pyruvate to ethanol

Question 6

What conditions is fate 1 under

Answer 6

anaerobic

eg. in yeast (by product of ethanol and CO2)

Question 7

What is fate 2

Answer 7

conversion of pyruvate to lactate

Question 8

What are the conditions of fate 2

Answer 8

in animals where demand for ATP outweighs production in mitochondria (anaerobic)

Question 9

true or false; even in fully oxygenated resting muscle cell about half of glucose which enters glycolysis is converted to lactate

Answer 9

true

Question 10

what do you call the process in which: lactate is transferred from muscle to the liver; and the transfer of glucose from liver to muscle

Answer 10

cori cycle

Question 11

What is fate 3

Answer 11

pyruvate/ alanine cycle

Question 12

what are the conditions of pyruvate/alanine cycle

Answer 12

• pyruvate generated in muscle and other tissues can be converted to alanine
• then returned to liver ( converted to pyruvate; used as gluconeogenic substrate; or oxidized in the TCA cycle) for gluconeogenesis
• requires alpha amino acid to be a donor of an amino group

Question 13

significance of the pyruvate alanine cycle

Answer 13

indirect way for the muscle to get ride of nitrogen; while replenishing its energy supply

Question 14

What does the pyruvate/alanine cycle allow for the non hepatic tissues?

Answer 14

allows non hepatic tissues to deliver the amino portion of catabolized amino acids to the liver for excretion as urea in the kidneys

Question 15

What is fate 4

Answer 15

conversion of pyruvate to oxaloacetate

Question 16

true or false; fate 4 is the first step of gluconeogenesis

Answer 16

true; involves the carboxylation of pyruvate by pyruvate carboxylase to oxaloacetate

Question 17

where does fate 4 occur

Answer 17

mitochondria

Question 18

what does fate 4 use?

Answer 18

carboxylated biotin factor as the CO2 source

ATP as the free energy source

Question 19

Why is fate 4 important?

Answer 19

when the cell has too much acetyl CoA; more than needed to supply the TCA cycle; acetyl CoA activates pyruvate carboxylase in an allosteric manner and diverts pyruvate to oxaloacetate production

Question 20

What is fate 5

Answer 20

conversion of pyruvate to acetyl CoA

Question 21

What are the conditions for fate 5

Answer 21

anaerobic

multi enzyme complex pyruvate dehyrogenase converts pyruvate to acetyl CoA

Question 22

Where is fate 5

Answer 22

inside the mitochondria

Question 23

true or false; fermentation allows for NAD+ to be regenerated

Answer 23

true ( glycolysis and ATP production can then proceed without the involvement of oxygen)

Question 24

true or false: when oxygen is present, additional ATP can be generated when NADH delivers its electrons to the electron transport chain; regardless of the presence of O2 glycolysis will continue

Answer 24

true

Question 25

what gluconeogenesis and where does it occur?

Answer 25

in the liver

- reversal of glycolysis

Question 26

what is the role of the liver to the muslce

Answer 26

to supply the muscle with fresh incomming glucose so glycolysis and energy production can keep going

Question 27

What does alanine serve as

Answer 27

carrier of ammonia

Question 28

Why does alanine inhibit pyruvate kinase

Answer 28

alanine is used to make glucose from pyruvate; it is therefore not desirable to pyruvate kinase active under these conditions as it would regenerate pyruvate