Lecture 16 - Citric Acid 2 Flashcards
(14 cards)
Why is the citric acid cycle also called the Krebs cycle and the Tricarboxylic acid cycle
CAC because the ‘first’ product is citrate.
TCA cycle because citrate is not the only tricarboxylic acid in the cycle
Why is the citric acid cycle commonly studied
It is a process that could be manipulated for biotechnology
Flow through it is reduced/stopped in cancer – possible therapy
Some interesting features that are seen repeated in other systems
Several intermediates appear to function as signalling molecules controlling the cell
What does the citric acid cycle do
Final oxidation pathway for all fuel molecules
Generates some ATP and ‘high energy’ electron carriers that can produce more ATP
Produces intermediates that can feed biosynthetic pathways
How does the citric acid cycle work
Oxidation reactions:CO2 release via decarboxylationcarbon-carbon double bond formationremoval of hydroxyl groups
What is the overview of the CAC
Acetyl part of acetyl-CoA combines with a four carbon molecule to form a six carbon molecule. Through rearrangement, that six carbon can be made in to a form that can lose a carbon dioxide to form a five carbon molecule, then lose another carbon dioxide to form a four carbon molecule. That four carbon molecule can then be rearranged to reform the starting material, so the cycle can start again.
What does citrate synthase do
Catalyses synthesis of citrate from OAA and Acetyl CoA
Why is citrate hard to oxidise further
the carbon is already partially oxidised and has no hydrogen available to remove
a rearrangement of this can lead to the hydroxyl being on a different carbon
What is citrate converted to and by what
Aconitase enzyme converts it to cis-aconitate then isocitrate, without releasing the sibstrate
What does isocitrate dehydrogenase do
Converts isocitrate to 2-oxoglutarate
aka alpha-ketoglutarate
What does the 2-oxoglutarate dehydrogenase complex do
converts alpha-ketoglutarate into succinyl CoA
What are the parts of the 4 step rearrangement in the CAC
Succinyl-CoA –Succinate thiokinase–> succinate
Succinate –Succinate Dehydrogenase–> Fumarate
Fumarate –Fumerase–> Malate
Malate–Malate dehydrogenase–> OAA
What is used in the citric acid cycle
1 x acetyl-CoA
3 x NAD+
1 x FAD
1 x ADP
1 x Pi
What is produced in the CAC
2 x CO2
3 x NADH + H+
1 x FADH2
1 x ATP
What is the net yield of ATP per acetyl CoA in the CAC
10
