Question

Fill in the blanks with the appropriate words.
In an eukaryotic cell, the breakdown of one molecule of glucose to six molecules of $C{O}_2$ causes formation of a total of .......... molecules of ATP, of which .......... are formed in the mitochondrion.

Answer 1

• Break down of glucose for cellular respiration starts with glycolysis where one molecule of glucose is broken down to 2 molecules of Pyruvic acid and there is a net gain of 2 ATP and 2 NADH molecules.
• One molecule of pyruvic acid enters the Kerb cycle which takes place in mitochondria and it produces one molecule of ATP, 4 molecules of NADH , one molecule of FADH and one molecule of GTP.
• So after 2 pyruvic acid are through the cycle 2 ATP, 8 NADH, 2 FADH and 2 GTP molecules are produced.
• NADH and FADH molecules then enter the electron transport chain and under go oxidative phosphorylation where one molecule of NADH produces 3 ATP and one molecule of FADH gives 2 ATP.
• The GTP is converted to ATP.
• So 8 NADH gives 24 ATP and 2 FADH gives 6 ATP.
• Now the net gain of ATP by breaking down of one molecule of glucose is

Glycolysis 2 ATP 2 ATP

2 NADH 6 ATP

Kerb cycle 2 ATP 2 ATP

(2 pyruvic acid) 8 NADH 24 ATP

2 FADH 4 ATP

2 GTP 2 ATP

TOTAL 40 ATP

• Therefore total ATP production by break down of one molecule of glucose is 40 ATP from which 2 ATP are produced in cytoplasm and 36 in mitochondria.
• Therefore the answer in the first blank is 40 and the answer in the second blank is 3.