Respiration in Plants

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01

ÅLÇØHØLÏÇ FËRMËÑTÅTÏØÑ:

Here, the pyruvic acid formed from glucose is

converted to CO2 and ethanol. (AIPMT 1997) The

enzymes, pyruvic acid decarboxylase and alcohol

dehydrogenase catalyze these reactions. E.g.

Yeast. Yeasts poison themselves to death when

the concentration of alcohol reaches about 13%

Sugar

CO2 + Ethanol + Energy

yeast

02

LÅÇTÏÇ ÅÇÏD FËRMËÑTÅTÏØÑ:

Here, pyruvic acid is converted to lactic acid.

No CO2 is released (NEET 2014) E.g. In muscle

cell, some bacteria.

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The reducing agent (NADH + H⁺) is reoxidized to NAD⁺ in both the

processes.

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In animals, when oxygen is inadequate during exercise, pyruvic acid in

muscle cells is reduced to lactic acid by lactate dehydrogenase.

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Net ATP production from fermentation of one glucose molecule = 2. (Out

of 4 ATP from glycolysis 2 ATP are utilized in fermentation).

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The steps involved in fermentation are shown below:

Glucose

Glyceraldehyde

3-Phosphate

3-Phosphoglyceric

acid

Phosphoenol

Pyruvic acid

Pyruvic

acid

Lactic

acid

NAD⁺

NAD⁺

Ethanol + CO2

NAD⁺

NADH + H⁺

NADH + H⁺

NADH + H⁺