Glycerophosphate’s shunt

2DOAP+2NADH2à2phosphoglycerate+2NAD (in cytosol)

2phosphoglycerate+2FADà2DOAP +2FADH2 (in mitochondrions), each FADH gives 2x2=4ATP

Malate’s shunt

2oxaloacetic acid+2NADH2à2malate+2NAD (in cytososl)

2malate+2NADà2oxaloacetic acid +2NADH2 (in mitochondrions), each NADH2 gives 2x3=6 ATP

Thus, energetic value of aerbic oxidation of glucose makes up 36 ATP (in the case of glycerophosphate’s shunt) or 38 ATP in the case of malate’s shunt.

Pentose phosphate’s cycle

This process occurs in cytosol with participation of many enzymes in anaerobic conditions. A main enzyme is glucose-6-phosphate dehydrogenase (with coenzyme NADPH2):

1) 6glucose-6-phosphate+12NADPH2à12NADP+6Pentose-5-phosphate+6CO2 (glucose-6-phosphate-dehydrogenase)

2) 6Pentose-5-phosphateà4frucose-6-phosphate+2PGA

3) 2PGAàfructose-6-phosphate

4) 4frucose-6-phosphate+ fructose-6-phosphateà5 fructose-6-phosphate

5) 5 fructose-6-phosphateà5glucose-6-phosphate

The importance of PPC:

1. This is a source of NADPH2 for biosynthesis of FFA, cholesterol, ketone bodies, NO etc; hydroxylation reactions; reductive amination, reduction of glutathione and action of NADH-oxidase of blood cells

2. This is a source of pentoses which are used on formation of nucleic acids, coenzymes, nucleoside tri- and diphosphates, GAG

3. This is a way of conversion of pentoses excess to glucose

The resemblance and differences between glycolysis and pentose’s cycle

Both processes occur in cytosol in anaerobic conditions and beginn from phosphorylation of glucose; some intermediates are the same, e.g. fructose-6-phosphate and phosphoglyceraldehyde.

Differences:

Glycolysis:

1. ATP is formed. ATP is a universal source of energy for many processes including proteins biosynthesis etc

2. Glucose is broken up to phosphotrioses. Full cleavage demands oxygen and occurs in mitochondrias;

3. Intermediates of glycolysis may be used for lipids and glucose formation;

4.Glycolysis occurs mainly in muscles

PPC:

1. NADPH2 are formed. They’re sources of energy for biosynthesis of FFA, cholesterol, ketone bodies and corticoids

2. Glucose is completely broken up in anaerobic conditions

3. Intermediates are used for nucleic acids, coenzymes, nucleoside tri- and diphosphates, GAG

4. It occurs in erythrocytes and leukocytes, adipose and nervous tissues, mammary and thyroid glands, liver

<== попередня сторінка	\|	наступна сторінка ==>
Gluconeogenesis and Cori cycle	\|	Elimination of final products of carbohydrates metabolism

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