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A Handbook of Biology

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Comparison between fermentation & aerobic respiration

Fermentation

Aerobic respiration

Partial breakdown of glucose.

Complete breakdown of glucose to

CO2 & H2O.

Net gain of only 2 ATP.

Net gain of 36 ATP.

NADH is oxidised to NAD⁺ rather slowly

NADH is oxidised to NAD⁺ very

vigorously.

ÅMPHÏBØLÏÇ PÅTHWÅÝS

Glucose is the favored substrate for respiration. So, all carbohydrates are

first converted to glucose for respiration. Other substrates are also respired,

however they do not enter at the first step in the respiratory pathway.

There respiratory pathway is generally considered

as a catabolic pathway. However it also involves both

anabolism (synthesis) and catabolism (breakdown). So it

is better called as an amphibolic pathway. (AIPMT 2009)

Fats

break

down

into

glycerol & fatty acids. Fatty

acids are degraded to acetyl

CoA and enter the pathway.

Glycerol is converted to PGAL

and

enters

the

pathway.

(NEET II 2016)

Proteins

are

degraded

by

proteases

into

amino

acids. Each amino acid (after

deamination)

enters

the

pathway at some stage in the

Krebs’ cycle or as pyruvate or

acetyl CoA. (NEET II 2016)

Fats

Carbohydrates

Proteins

Amino acids

Glucose 6-phosphate

Fructose 1, 6 biphosphate

Dihydroxy Acetone Phosphate

Glyceraldehyde 3-phosphate

Pyruvic acid

Acetyl CoA

Krebs'

cycle

H2O

CO2

Fatty acids and glycerol

Simple sugars

e.g., glucose