Lecture 5 - Krebs Flashcards
Site and purpose of Krebs
Still in the liver, but now in the mitochondrial matrix
- large pores in the outer membrane let pyruvate diffuse through but crossing the inner membrane requires a pyruvate-specific membrane carrier (this active transport is powered by entropy created by liberating CO2 and extra energy is avaliable to reduce NAD+)
Step 1 of Krebs
2 Pyruvate (3C) enter from glycolysis
- NAD+ to NADH
- losses a Carbon (as CO2) and add coA to form acetyl-coA
enzyme: pyruvate dehydrogenase
purpose of acetyl-coA
so that the pyruvate can enter the mitochondrial membrane and then the matrix
Step 2 of Krebs
Acetyl-coA binds to Oxaloacetate (oaa) to form citrate
- removal of coA
enzyme: citrate synthase
Step 3 of Krebs
- Rearranged 6C citrate into isocitrate through removal and addition of water
enzyme: aconitase
Step 4 of Krebs
lose C (in the form of CO2) to form alpha-ketogluturate (5C)
- NAD+ to form NADH
enzyme: iso-citrate dehydrogenase
Step 5 of Krebs
Lose a C (in the form of CO2) and gain coA to form succinyl coA (4c)
NADH formation
enzyme: alpha-ketoglutarate dehydrogenase
Step 6 of Krebs
remove coA to form succinate (4C)
- GDP turns into GTP from the energy released via coA removal and Pi
- GTP can be converted to ATP
- Pi remains, hangs out
enzyme: succinyl coA synthase
Step 7 of Krebs
Succinate forms Fumuarate (4C)
- formation of FADH2 and FAD
enzyme: succinate dehydrogenase
Step 8 of Krebs
Fumarate turns into malate and + H2O
enzyme: Fumuarase
Step 9 of Krebs
Malate forms OAA via oxidation
- NAD+ to form NADH
enzyme: malate dehydrogenase
Step 10 of Krebs
OAA is available to combine with acetyl-coA so that it regenerates the cycle
Without glucose what would happen to OAA
the body will turn it into glucose
Products
4 CO2
6 NADH
2 FADH2
2 ATP
Mnemonic for Krebs
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Citrate
Isocitrate
Alpha-ketoglutarate
Succinyl-CoA
Succinate
Fumarate
Malate
OAA
mnemonic for enzymes
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Citrate synthase
Aconitase
Isocitrate dehydrogenase
Alpha-ketoglutarate dehydrogenase
Succinyl-CoA synthetase
Succinate dehydrogenase
Fumarase
Malate dehydrogenase
citric acid cycle and accumulation of ATP
If the produces of the citric acid cycle are in high demand, then the citrate would not accumulate in the cell, increase citrate concentration suggest ATP supply is low
