TCA cycle Flashcards
What does each turn of the TCA cycle produce?
2 CO2 molecules = waste
3 NADH
1 GTP
1 FADH2
What are the characteristics of Krebs cycle enzymes?
Soluble proteins located in mitochondrial matrix
What conditions does TCA cycle operate and why?
Aerobic conditions
Re-oxidation of coenzymes needed to produce ATP, so FADH and NADH need to transfer their electrons in OP, if the next step doesn’t occur this can’t either
What enters the TCA cycle?
When pyruvate is converted to to acetyl CoA, it combined with 4 carbon Oxaloacetate creating 6 carbon citrate
Amino acids can also enter the TCA cycle
Why can amino acids be used in the TCA cycle?
Amino acid degradation involves breaking down the amino group which is excreted at urea
The carbon skeleton can then enter the TCA cycle or into the production of glucose
What molecules are created from the degradation of all 20 amino acids?
7 molecules:
Pyruvate Acetyl CoA Acetocetyl CoA a-ketoglutarate succinyl CoA Fumarate Oxaloacetate
( all of which can be part of the krebs cycle )
What does of reaction is a transamination reaction?
Group transfer ( between the amino and carboxyl group )
What occurs in the reaction between
alanine + a-ketoglutarate –> ?
alanine + a-ketoglutarate –> pyruvate + glutamate
enzyme : alanine transferase
Then pyruvate can enter the TCA cycle
How do NADH electrons cross from the cytosol into the mitochondria for OP in the skeletal muscle and brain ?
Glycerol phosphate shuttle
How do NADH electrons cross from the cytosol into the mitochondria for OP in the liver, kidney and heart ?
Malate - aspartate shuttle
Describe the steps in the glycerol phosphate shuttle?
- Cytoplasmic glycerol 3 phosphate dehydrogenase converts NADH –> NAD+ during the reaction between DHAP to glycerol 3 phosphate
The electrons now are in glycerol 3 phosphate
During the reaction of glycerol 3 phosphate back to DHAP , Mitochondrial glycerol 3 phosphate dehydrogenase converts FADH2 ( which was made from the reaction ) back to FAD
The electrons in FAD then get passed to co-enzyme Q, part of the electron transport chain
How does the Malate Aspartate shuttle work?
Aspartate –> oxaloacetate ( aspartate transaminase )
oxaloacetate –> malate ( malate dehydrogenase )
The malate is then shuttled into the mitochondria
malate is then reversed to oxaloacetate and then aspartate ( NAD+ –> NADH) and ( glutamate –> a-ketoglutamate ) and same enzymes.
Aspartate removed with antiporter back out into the cycle.
How many molecules of ATP is produced by the oxidation of 1 acetyl CoA?
3 NADH = 3 x 3 = 9
1 FADH = 1 x 2 = 2
+ 1 GTP
= 12 ATP
What enzymes can become mutated to cause cancer?
These mutations decrease TCA activity and increase aerobic glycolysis leading to lactate - Warburg effect
Isocitrate dehydrogenase, succinate dehydrogenase, fumerase = activity is decreased when mutated
