Aerobic Metabolsim Flashcards
What are the other names for the TCA cycle?
Krebs/citric acid
What are the main principles of the TCA cycle?
The oxidation of acetyl CoA —> CO2 & H2O
Where does the TCA cycle occur?
In the mitochondrial matrix.
Where in which cell types does the TCA cycle NOT occur?
- RBC’s
- White muscle fibres (fast twitch)
What happens to the pyruvate before it can enter the TCA cycle?
What is this reaction called?
What are the starting molecules and the products of the reaction?
What other molecules are required?
The pyruvate is converted into acetyl CoA.
The reaction is called the link reaction.
It takes pyruvate + CoA —> acetyl CoA + CO2.
NAD+ is also required, as this is reduced to NADH in the process as the pyruvate is oxidised.
Which part of the CoA molecule is important for the binding with pyruvate?
What type of bond does it form?
It is the SH that is important.
It forms a thioester bond with the carboxylic acid (COOH) group on the pyruvate.
How many reactions are involved in the TCA cycle?
X8
What is the first reaction in the TCA cycle?
What are the before and after molecules?
What enzyme catalyses this reaction?
What happens to the CoA part of the acetyl CoA?
Acetyl CoA + Oxyloacetate —> citrate
Enzyme = citrate synthase
The CoA breaks away and is not part of the new citrate molecule.
Acetyl CoA is a how many carbon molecule?
X2
Oxaloacetate is a how many carbon molecule?
X4
Citrate is a how many carbon molecule?
X6
What is the second reaction in the TCA cycle?
What are the before and after molecules?
What enzyme catalyses this reaction?
It is an isomerase reaction, where the OH (hydroxyl) group is moved within the molecule.
Citrate —> isocitrate
Enzyme = aconitase
What is the third reaction in the TCA cycle?
What are the before and after molecules?
What enzyme catalyses this reaction?
What other molecules are involved in this process?
This is the first loss of CO2 in the TCA cycle.
Isocitrate —> alpha-ketogluterate
Enzyme = isocitrate dehydrogenase
NAD+ is reduced to NADH as the isocitrate is oxidised.
What is the fourth reaction in the TCA cycle?
What are the before and after molecules?
What enzyme catalyses this reaction?
What other molecules are involved in this process?
This is the second loss of CO2 in the TCA cycle.
Alpha-ketogluterate —> succinyl CoA
Enzyme = ketogluterate dehydrogenase
NAD+ is reduced to NADH as the alpha-ketogluterate is oxidised.
CoA is also required to be put in at this step.
What is the fifth reaction in the TCA cycle?
What are the before and after molecules?
What enzyme catalyses this reaction?
What other molecules are involved in this process?
Succinyl CoA —> succinate
Enzyme = succinate thiokinase
Called a thiokinase as it is a phosphorylation (‘..kinase’) using the energy of the thioester bond (‘thio..’) where the CoA molecule was bonded.
It phosphorylates GDP —> GTP using an INORGANIC PHOSPHATE (Pi) and NOT a phosphate from the substrate, therefore it is NOT a substrate level phosphorylation.
