TCA Cycle Lecture 58

Biochem CUSOM

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Responsible for turning pyruvate into acetyl CoA:Why is this important?
Pyruvate dehydrogenase complex (PDC) is responsible for turning pyruvate into acetyl CoA so that it can enter the Citric Acid cycle.
Overall scheme of the transformation of pyruvate:
Pyruvate------->decarboxylation---->oxidation----->transfer to CoA---->Acetyl CoAIn other words: Pyruvate----->remove CO2---->remove electrons----->add to CoA-----> Acetyl CoA
What does PDC need?
Cofactors
What are the two types of cofactors?
Catalytic: cofactors are used by the complex and regenerated hence the name catalytic.Stoichiometric: cofactors are used but not regenerated.
Fat soluble vitamins:
Fat soluble: Vitamin A, D, E, K
Water Soluble vitamins
Water soluble: B complex and C Thiamine (B1) Riboflavin (B2) Pantothenic acid (B5) Niacin (B3) Lipoic acid
Examples of catalytic cofactors:
Thiamine (B1)Lipoic acidRiboflavin (B2): used as FAD
Examples of stoichiometric cofactors:
Pantothenic acid (B5): used as coenzyme ANiacin (B3): used as NAD+
Explain significance of pyruvate to acetyl CoA:
Pyruvate--->Acetyl CoA is irreversible. Once it becomes acetyl CoA, it can not go backwards and form pyruvate
Explain PDH complex of 3 enzymes
PDH is a complex made up of three enzymes 1. Pyruvate Dehydrogenase E1 catalyzes steps 1-22: Dihydrolipoyl Transacetylase E2 catalyzes step 33: Dihydrolipoyl Dehydrogenase E3 catalyzes steps 4-5
What is PDH inhibited by? examples
PDH Complex is inhibited by HIGH ENERGY
  • ATP
  • NADH
  • Acetyl CoA
What is PDH stimulated by?
PDH is stimulated by LOW ENERGY
  • CoA
  • NAD+
  • AMP
Phosphorylates pyruvate dehydrogenase E1 (PDH) making it less active.
Pyruvate dehydrogenase kinase
Kinase=halt _________
PDH's activity
When the body needs energy, there are a lot of _________.What will this do?
ADP floating around. ADP will inhibit kinase activity.