216 ^|

A Handbook of Biology

Energy production is limited. Less than

7% of the energy in glucose is released

and not all of it is trapped as high energy

bonds of ATP. Hazardous products (acid

or alcohol) are formed

DRÅWBÅÇK ØF FËRMËÑTÅTÏØÑ

ÅËRØBÏÇ RËSPÏRÅTÏØÑ



It is a complete oxidation of organic substances in the presence of

oxygen releasing CO2, water & energy.



It occurs in mitochondria.



For this, the pyruvate (final product of glycolysis) is transported from the

cytoplasm into the mitochondria.



The crucial events in aerobic respiration are:



Complete oxidation of pyruvate by stepwise removal of all the

hydrogen atoms, leaving 3 CO2 molecules. It takes place in the

matrix of mitochondria.



Passing on of electrons removed as part of H-atoms to molecular O2

with simultaneous synthesis of ATP. It occurs on the inner membrane

of mitochondria.



Pyruvate (pyruvic acid) enters mitochondrial matrix and undergoes

oxidative decarboxylation in presence of pyruvic dehydrogenase. It

needs several enzymes, NAD⁺ & Coenzyme A. (NEET 2018)



During this process, 2 NADH molecules are produced from 2 pyruvic acid

molecules.

Pyruvic acid + CoA + NAD⁺

Acetyl CoA + CO2 + NADH + H⁺

Mg²⁺

Pyruvate dehydrogenase



Acetyl CoA then enters tricarboxylic acid (TCA) cycle.

TRÏÇÅRBØXÝLÏÇ ÅÇÏD ÇÝÇLË ( KRËB'S ÇÝÇLË ØR ÇÏTRÏÇ ÅÇÏD ÇÝÇLË)

TCA cycle was first elucidated by Hans Krebs.

Steps:



Condensation of acetyl group with oxaloacetic acid (OAA) & water to

form citric acid in presence of citrate synthase enzyme. A CoA molecule

is released.