1

SURVEY OF BIOCHEMISTRY

Glycogen

2

2 Ways To Generate Glucose

Glycogenolysis Gluconeogenesis

Break down of glycogen

Glucose Glucose1-Phosphate

Glucose 6-Phosphate

Synthesis of glucose fromnon-carb precursors

Lactate Pyruvate

3

Energetics of Reversing Glycolysis

Glucose

Pyruvate

Hexokinase ∆G° = -17 kJ/mol

Phosphofructokinase ∆G° = -14 kJ/mol

PyruvateKinase ∆G° =

-31 kJ/mol

Reversing glycolysis is not energetically feasible!

Ref: Rodney Boyer Interactive Concepts in Biochemistry

4

Pyruvate to Phosphoenolpyruvate

Dilemma:• Oxaloacetate can only be generated from pyruvate in the mitochondria

• Pyruvate gets synthesized initially in the cytosol

5

PEP and Oxaloacetate Transport

Fig 16-20 does not show pyruvate!

Draw another viewof this process thatmay be more helpful

6

Gluconeogenesis

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Energetics Revisited

∆G value comparisons

By what mechanisms

do these enzymes

work?

8

Pyruvate Carboxylase Cofactor

9

Enzyme-Cofactor Complex

10

Pyruvate Carboxylase

11

Pyruvate Carboxylase

12

PEPCK Mechanism

13

Ch. 16 Overview

• 16-1 Glycogen Breakdown (Fri)

• 16-2 Glycogen Synthesis (Wed)

• 16-3 Control of Glycogen Metabolism (Wed)

• 16-4 Gluconeogenesis (Mon)

14

Enzymes in Glycogen Synthesis

• UDP-Glucose Pyrophosphorylase

• Glycogen Synthase

• Glycogen Branching Enzyme

15

UDP-Glucose Pyrophosphorylase

UDP-GlucosePyrophosphorylaseactivates glucosyl

units

PPi

16

Glycogen Synthase

17

Glycogen Branching Enzyme

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Overview

19

PRS

• Which of the following enzymes is involved in gluconeogenesis?

1. Pyruvate carboxylase2. Pyruvate kinase3. Phosphofructokinase4. Glycogen synthase

20

PRS

• Which of the following is not a product of glycolysis?

1. Pyruvate2. Fructose 1,6-Bisphosphate3. Oxaloacetate4. Glucose 6-Phosphate

21

PRS

• Which enzyme produces glucose 1-phosphate?

1. Hexokinase2. Glycogen Debranching Enzyme3. Glycoen Branching Enzyme4. Glycogen Phosphorylase