Citric Acid Cycle

Question 1

Function of the citric acid cycle

Answer 1

common metabolic pathway for all “fuel” molecules (carbohydrates, fatty acids, amino acids)

occurs in mitochondria

yields just 2ATP

“gateway” to aerobic respiration

does not produce ATP directly or include O2 as a reactant

removes e’s and passes them on to form NADH and FADH2

produces 90% of aerobic cell energy

Question 2

Process of the citric acid cycle

Answer 2

the acetyl group from acetyl CoA is attached to a four-carbon oxaloacetate molecule to form a six-carbon citrate molecule

Through a series of steps, citrate is oxidised, releasing two carbon dioxide molecules for each acetyl group fed into the cycle

Two further steps of oxidation and decarboxylation occur during the cycle ultimately oxidizing all 3 carbons contained in the initial pyruvate to CO2

Question 3

Reactions that involve electron carriers

Answer 3

oxidations require electron carriers such as NAD+ and FAD to link this process to the processes of terminal respiration

Question 4

Formation of Acetyl CoA

Answer 4

pyruvate from glycolysis and fatty acids are oxidised further to acetyl CoA in the mitochondrial matrix

Acetyl CoA sits in the centre of energy production for the cell as it allows different intermediates into the main energy producing pathway of the citric acid cycle

pyruvate dehydrogenase catalyses reaction of pyruvate - acetyl CoA

Question 5

Reactions that release C02

Answer 5

formation of Acetyl CoA by pyruvate dehydrogenase

oxidation and decarboxylation during the cycle

Question 6

links to other metabolic pathways

Answer 6

NAD+ and FAD links process to terminal respiration

oxidising pyruvate-acetyl CoA links anabolic and catabolic processes for carbohydrates, lipid and amino acids and provides important substrates for biosynthesis of other metabolic compounds