Respiration in Plants

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During the glucose catabolism, not all the liberated energy goes out as

heat. Glucose is oxidized in several small steps. It enables some steps

to be just large enough that energy released can be coupled to ATP

synthesis.

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During respiration, oxygen is utilized, and CO2, water & energy are

released. C6H12O6 + 6O2 ® 6CO2 + 6H2O + Energy

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Certain organisms are adapted to anaerobic conditions. Some are

facultative anaerobes. Others are obligate.

GLÝÇØLÝSÏS (ËMP PÅTHWÅÝ)

Its

scheme

was

given

by

Gustav

Embden,

Otto

Meyerhof & J. Parnas. So it is

also known as EMP pathway.

3

It is the partial oxidation

(breakdown) of glucose to

2 molecules of pyruvic acid

(C3H4O3) in the absence of O2

1

It occurs in cytoplasm

of all living organisms.

2

In anaerobes, it is the only

process in respiration..

4

In plants, glucose is derived from sucrose (end product of

photosynthesis) or from storage carbohydrates. Sucrose is

converted into glucose & fructose by an enzyme, invertase.

These 2 monosaccharides readily enter glycolytic pathway.

5

Glucose & fructose are phosphorylated to form glucose-6-

phosphate by the enzyme hexokinase. It is then isomerized

to produce fructose-6-phosphate (NEET 2019). Subsequent

steps of metabolism of glucose and fructose are same.

6

Glucose

Hexokinase

Triose Phosphate

Isomerase

Enolase

Pyruvate kinase

Phosphoglyceromutase

Phosphoglycerate kinase

Glyceraldehyde

-3-phosphate

dehydrogenase

Phospho

hexoseisomerase

Phospho fructokinase

Aldolase

(6C)

Glucose-6-phosphate

(6C)

Fructose-6-phosphate

(6C)

Fructose1,6-bisphosphate

(6C)

Triose phosphate

(glyceraldehyde-3-phosphate)

(3C)

Triose

phosphate

(Dihydroxy

acetone

phosphate)

(3C)

2 × Triose bisphosphate

(1,3 bisphosphoglyceric acid)

(3C)

2 × Triose phosphate

(3-phosphoglyceric acid)

(3C)

2 × 2-phosphoglycerate

2 × phosphoenolpyruvate

2 × Pyruvic acid

(3C)

(2) ADP

(2) ATP

(2) ADP

ATP

ADP

ATP

ADP

2NADH+H

+

2NAD

+

(2) H2O

(2) ATP