Glycogen, TCA Cycle and Mitochondria (Lecture 11)

Question 1

regulation of CAC (3)

Answer 1

1. energy state of the cell, through allosteric activation of isocitrate dehydrogenase via ADP
2. redox state of the cell, through the mitochondrial ratio of NADH/NAD+
3. availability of energy rush compounds (acetyl coa, succinyl coa) that inhibit CAC enzymes (citrate synthase and alpha KGDH)

Question 2

how is oxaloacetate transported out of the mitochondria

Answer 2

converted to aspartate

Question 3

citrate and FA synthesis

Answer 3

citrate is a carrier of acetyl cola, thus when interacting with citrate lyase, acetyl coa can be released into the cytoplasm

Question 4

when oxaloacetate is pout of the mitochondria, what may happen

Answer 4

decarboxylated and phsophoryalted by PEPCK to make PEP

PEP–> G6P –> glucose

Question 5

anapleurosis in CAC causes:

Answer 5

1. PYRUVATE CARBOXYLASE
   decreased CAC flux

increase acetyl coa

activate pyruvate carboxylase (allosterically via acetyl coa)

pyruvate decarboxylase will synthesized oxaloactat to increase the generation of all CAC intermediates

2. TRANSAMINASE
   pyruvate accepts an amino group from glutamate to generate alpha KG and replenish CAC intermediates

Question 6

reactions that replenish oxaloacetate

Answer 6

pyruvate carboxylase (pyruvate)

PEP carboxylase (PEP)

transamination (aspartate)

these are feed forwards since replenishing oxaloacetate stimulates its own usage

Question 7

replenish malate

Answer 7

pyruvate –> malate via malic enzyme

Question 8

aspartate transaminase

Answer 8

glutamate + oxaloacetate alpha KG + aspartate

transamination requires an AA and a keto acid

Question 9

glutamate dehydrogenase

Answer 9

transamination reaction used to regenerate alpha KG from glutamate (via GDH and NAD+)

theoretically reversible, but the Km for GDH to bind with ammonia required for the reversible reaction is very high and nears toxic levels. therefore the reaction is unidirectional in living cells

glutamate + NAD+ –> alpha KG + NADH