Metabolic Fates of Pyruvate- Wimmer

Question 1

what is lactic acidosis?

Answer 1

build up of lactate due to lack of oxygen for ETC

Question 2

what is most common cause of metabolic acidosis?

Answer 2

lactic acid build up

Question 3

what determines if pyruvate will continue with glycolysis or will become lactic acid?

Answer 3

NAD+ recycling

NAD needed at glyceraldehyde-3-phosphate dehydrogenase reaction

Question 4

what happens to reducing equivalents in aerobic tissues?

Answer 4

malate or glycerol-P shuttle carry reducing equivalents to ETC

Question 5

what happens to reducing equivalents in anaerobic tissues?

Answer 5

NADH gies reducing equivalents to pyruvate, forming lactate

catalyzed by lactate dehydrogenase

Question 6

what cells are purely anaerobic?

Answer 6

mature RBC- lack mitochondria

Question 7

where does the backup begin when tissues lack oxygen?

Answer 7

ETC- becomes completely reduced, so more electron carriers can’t dump reducing equivalents
NADH builds up and activates lactate dehydrogenase so reducing agents can give electrons to pyruvate

Question 8

what happens to pyruvate carbons in anaerobic tissues?

Answer 8

lactate dehydrogenase pyruvate + NADH –> lactate + NAD

Question 9

what happens to pyruvate carbons in aerobic tissues?

Answer 9

pyruvate dehydrogenase and TCA cycle

Question 10

what is the final electron acceptor in aerobic conditions?

Answer 10

water (oxygen)

Question 11

what is the final electron acceptor in anaerobic conditions?

Answer 11

lactate

Question 12

how many ATP are made under aerobic conditions?

Answer 12

30-32 (depending on what shuttle is used)

Question 13

how many ATP are made under anaerobic conditions?

Answer 13

2 via substrate level phosphorylation

Question 14

what cells normally produce lactic acid?

Answer 14

RBCs and exercising muscle

Question 15

what tissues are all aerobic?

Answer 15

brain and liver

Question 16

what two ways is lactate used to aid in clearance from blood normally?

Answer 16

• conversion to glucose by the liver (gluconeogenesis)
• energy production- lactate–>pyruvate–>acetyl-CoA–>CO2
  (also cleared by kidneys)

Question 17

what are conditions that can result in lactic acidosis and can be fatal?

Answer 17

increased lactate production

decreased lactate use/clearance

Question 18

what are symptoms of lactic acidosis?

Answer 18

nausea/vomitting
hyperventilation
irregular heart rate

Question 19

why is hyperventilation a symptom of lactic acidosis?

Answer 19

blood is acidic, so CO2 in lungs is high

hyperventilation is a way to clear excess CO2

Question 20

what are some possible causes of lactic acidosis?

Answer 20

• restriction in blood supply
• lack of oxygenation
• delayed clearance
• renal/hepatic dysfunction
• pyruvate dehydrogenase dysfunction

Question 21

what do hypoxia and cyanide poisoning do?

Answer 21

forces anaerobic metabolism

pyruvate forced to lactate, builds up

Question 22

what does cyanide poisoning do?

Answer 22

blocks complex 4 of ETC cycle

very quickly fatal

Question 23

what form of iron does CN bind to?

Answer 23

Fe 3+ (does not bind to Fe 2+ in hemoglobin)

Question 24

what else can lactate pyruvate be converted to?

Answer 24

alanine

Question 25

what happens during pyruvate dehydrogenase dysfunction?

Answer 25

pyruvate builds up but oxygen is still present so shuttle still work
reducing equivalents formed during glycolysis can still take NADH to ETC and some aerobic metabolism can happen
not all pyruvate is forced to lactate
recoverable