MCDB 310 Post lecture 18

Reactions of the Citric Acid Cycle

- Acetyl CoA enters cycle, come out as Co2

- 1st half: 3 irreversible steps occur 1,3,4

- Only goes in 1 direction

What does citric acid cycle produce?

3 NADH

FADH2

1 GTP

How is the Citric Acid Cycle A Major Metabolic Hub? What happens if intermediates are depleted?

Many citric acid intermediates, can make useful biosynthetic molecules

- if these intermediates get depleted, citric acid cycles cannot go on

What can citrate and a-ketoglutarate create?

What can succinyl and oxlaoacetate create?

Reactions that replenish the citric acid cycle: anaplerotic ("to fill up") reactions? Main product?

Oxaloacetate is main product of these replenishing reactions in order to continue doing CAC

- Malate is a product since it is one step away from oxaloacetate

First two fill up reactions are also seen where?

First two reactions in gluconeogenesis

Regulation of the Citric acid cycle balances what?

Regulation balances the supply of key intermediates with the demands of energy production

Regulation occurs at which several points?

- PDC (note this step generates the substrate for the citric acid cycle but is not part of the cycle itself)- 1st respiration step

- Citrate synthase (step 1)

- Isocitrate dehydrogenase complex (step 3)

- α-ketoglutarate dehydrogenase complex (step 4)

Regulation of the Citric acid cycle two things to know?

1.) Red arrows: irreversible step and 1st respiration step are the steps of regulation

2.) Make sure inhibitor and activators make sense, don't have to specially memorize.