CHE 211 Study Guide - Final Guide: Pyruvate Dehydrogenase Complex, Pyruvate Dehydrogenase, Allosteric Regulation
Organic Chemistry 2: Aerobic Respiration & Energy Production
Control of the Citric Acid Cycle
► The main objective of Krebs Cycle is to produce high energy compounds for ATP
synthesis this pathway needs to speed up when supplies of ATP is low, and slow
down when ATP is plentiful
► As with glycolysis, citric acid cycle responds to the energy needs of the cell
► Pathway speeds up when greater demand for energy
► Four enzymes / enzyme complexes are allosterically regulated (these enzymes are used
for oxidation of pyruvate)
- Several regulated steps demonstrate the importance of precise control
Allosterically Regulated Reactions
1) Conversion of pyruvate to acetyl CoA
- The enzyme pyruvate dehydrogenase is inhibited by high concentrations of:
• ATP
• Acetyl CoA
• NADH
2) Synthesis of citrate from oxaloacetate and acetyl CoA
- Reaction 1: the enzyme involved in the conversion of oxaloacetate to citrate is
inhibited when high levels of ATP are present in the cell
- Negative effector is high levels of ATP
3) Oxidation and dearolation of isoitrate to α- ketoglutarate
- Reaction 3: the enzyme is isocitrate dehydrogenase and it is activated high levels of
ADP and is in inhibited by high levels of NADH and ATP
- Positive effector, ADP controls this enzyme
- Inhibited by high levels of NADH and ATP
4) Conversion of α-ketoglutarate to succinyl CoA
- Reaction 4: the enzyme a-ketoglutarate dehydrogenase is activated by high levels of
ADP and inhibited by high levels of ATP, succinyl CoA and NADH
- Inhibited by high concentrations of:
• ATP
• Succinyl CoA
• NADH
Regulation of the Pyruvate Dehydrogenase Complex
• This is figure 22.6 from textbook summarizes the regulation of pyruvate
dehydrogenase complex and contains the citric acid cycle
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Document Summary
Organic chemistry 2: aerobic respiration & energy production. The main objective of krebs cycle is to produce high energy compounds for atp synthesis this pathway needs to speed up when supplies of atp is low, and slow down when atp is plentiful. As with glycolysis, citric acid cycle responds to the energy needs of the cell. Pathway speeds up when greater demand for energy. Four enzymes / enzyme complexes are allosterically regulated (these enzymes are used for oxidation of pyruvate) Several regulated steps demonstrate the importance of precise control. Allosterically regulated reactions: conversion of pyruvate to acetyl coa. The enzyme pyruvate dehydrogenase is inhibited by high concentrations of: atp, acetyl coa, nadh, synthesis of citrate from oxaloacetate and acetyl coa. Reaction 1: the enzyme involved in the conversion of oxaloacetate to citrate is inhibited when high levels of atp are present in the cell. Negative effector is high levels of atp: oxidation and de(cid:272)ar(cid:271)o(cid:454)(cid:455)lation of iso(cid:272)itrate to - ketoglutarate.
