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Biochemistry

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Carbohydrates

Question
16 out of 78
 

About glycolysis-true is



A Glucose to 3 C products

B Takes place in mitochondria

C Complete breakdown of glucose

D No ATP production

Ans. A Glucose to 3c. products

[ figure on the next page]

a. All the enzymes of glycosis pathway are found in extra mitochondrial soluble fraction of the cell, the cytosol.

b. In liver parenchymal cells and pancreatic cell, D-Glucose-6-phosphate is formed by glucokinase and in other places (tissues) by hexokinase

c. Hexokinase is inhibited in an allosteric manner by glu-6 phosphate. Hexokinase present in all cells except Liver and pancreatic cells, has high affinity (low Km) for its substrate glucose,. Function is to supply energy even in presence of low blood glucose. Function of glucokinase is to remove glucose from blood after meal, it has high km.

d. In Erythrocytes total 90% of energy produced by glycolysis, even in the presence of O2, final product is always Lactate. In white fibres of skeletal muscle — main source of energy is glycolysis

e. In fast growing cancer cells, glycolysis, proceeds at a much higher rate than is required by the citric acid cycle.

f. Phosphofructokinase is both an allosteric and an inducible enzyme whose activity is considered to play a major role in the regulation of glycolysis. (Rate limiting step)

g. Phosphoglycerate kinase is inhibited by Arsenate.

h. Insulin — activates glucokinase Hexokinase II & IV

i. Aldolase Enzyme: - Aldolase A —found in most of the tissues but Aldolase B found in liver and kidney

j. Hexokinase (Glucokinase), phosphofructokinase and pyruvate kinase — mediated reactions, are

irreversible and are major sites of regulation of glycolysis

Fig. of Glycolysis pathway

Fig.: The pathway of glycolysis. (P) — PO32-, P1 HOPO32; (-) inhibition. *Carbon atoms 1-3 of fructose bisphosphate form dihydroxyacetone phosphate, whereas carbons 4-6 form glyceraldehyde 3

- phosphate. The term b is -, as in bisphosphatase, indicates that. the phosphate groups are separated, whereas diphosphate, as in adenosine diphosphate, indicates that they are joined.

Pathway of glycolysis (Embden Meyerhof pathway) over all equation:

Glucose + 2ADP + 2Pi 2L(+) — Lactate + 2 ATP + 2H2O

(6-C) (3-C)

[ Note: Lactate is a 3 carbon substance]

11. ATP production during — Aerobic condition (per glucose)

Production of ATP:

1. Glyceraldehyde-3-phosphate dehydrogenase

2NADH (through Respiratory chain oxidation) = 5 ATP

2. Phosphoglycerate kinase

By oxidation at substrate level = 2 ATP

3. Pyruvate kinase

By oxidation at substrate level = 2ATP

Total production = 9 ATP

Consumption of ATP

(1) At Hexokinase

1 ATP

(2) At phosphofructokinase

1ATP

Total =2 ATP

Hence net gain during Aerobic condition = 9 — 2 = 7 ATP

12. During Anaerobic glycolysis only 4ATP production and 2 ATP consumed, so net gain 2ATP (since, there is no respiratory chain oxidation of NADH)

13. Arsenite or mercuric ions reacts with the —SHgp of lipoic acid and inhibit pyruvate dehydrogenase (that convert pyruvate to Acetyl co-A — to enter TCA cycle), as does a dietary deficiency of thiamine, allowing

pyruvate to accumulate that leads to lactate formation and Lacto acidosis (same in inherited deficiency of

pyruvate deHase)

Inherited deficiency of the Aldolase A and pyruvate kinase in RBC causes hemolytic Anaemia.

14. As shown in figure, enolase is inhibited by fluoride, the property that can be made use of when it is

required to prevent glycolysis in blood prior to estimation of glucose.

Carbohydrates Flashcard List

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