Part C- BIOC 3560 FINAL EXAM (Carbohydrates)

Rate-Limiting Steps

Metabolism- concepts

Glycolysis- review

1) Hexokinase.

3) Phospho-fructokinase-1.

10) Pyruvate kinase.

-Highly exergonic rxns.

- Are the regulated steps in glycolysis.

Hexokinase: about

Hexokinase I

Hexokinase IV (glucokinase)

Regulation of Hexokinase IV

Phosphofructokinase-1 allostery

PFK-1 regulation by ATP

Pyruvate kinase- Inhibition.

Pyruvate kinase regulation

Gluconeogenesis- The solution

Gluconeogenesis- precursors

1) Lactic acid (via pyruvate)

2) Glycerol (from lipids)

3) Some amino acids (termed glycogenic a.a.).

Glycolytic reactions in Gluconeogenesis

Gluconeogenesis Step 1

(Step 10 of glycolysis)

Conversion of pyruvate to phosphoenol-pyruvate (PEP)

Malate dehydrogenase in the Mitochondria vs. Cytosol

Gluconeogenesis Step 8

(Step 3 of glycolysis)

Fructose 1,6-bisphosphatase (FBPase-1).

Converts F 1,6-BisP to F 6-P.

-Is a phosphatase reaction (exergonic).

Gluconeogenesis Step 10

(Step 1 of glycolysis)

Step 3 (glycolysis)/ Step 8 (Gluconeogenesis):

Fructose 2,6-Bisphosphate

and Phosphofructokinase-1.

Fructose 2,6-Bisphosphate

and 1,6-Bisphosphatase.

Enzymes controlling

2,6-bisphosphate concentration.

PFK-2/FBPase-2 regulation

Step 10 (glycolysis)/ Step 1 (Gluconeogenesis):

Reciprocally regulated by____

Acetyl-CoA

Pyruvate Kinase Regulation

(again- but different)

Pyruvate to Oxaloacetate:

Pyruvate Carboxylase

Oxaloacetate to PEP:

PEP carboxykinase

Pyruvate carboxylase:

- Acetyl-CoA (+)

- ADP (-)

PEP carboxykinase

- ADP (-)

Pentose Phosphate Pathway:

Two phases

1. Oxidative.

2. Non-oxidative.

Oxidative & Non-oxidative pathway

of pentose phosphate pathway

Non-Oxidative phase

of pentose phosphate pathway

Regulation of Pentose Phosphate Pathway

Glycogen Synthesis- Making the precursor

Glycogen synthase reaction

Regulation of Glycogen Metabolism

Glycogen Metabolism- Phosphorylation &

Dephosphorylation.

Glycogen phosphorylase

Relationship of Glycogen synthase and glycogen phosphorylase

The enzymes are reciprocally regulated by phosphorylation.

Liver Carbohydrate metabolism- Regulated by PKA.

Enzyme activity

(Hormone-regulated)

Coordinates metabolism

(tissue-specific).

Differences in Muscle and Liver metabolism: Tissue-specific metabolism