Question

Explain the functions of NAD+ and FAD and the need for them in cellular respiration.

The cellular respiration of glucose yields less energy than the burning of glucose. What do you think happened to that excess energy in cellular respiration

What is the bond energy of glucose and how is it calculated?

Please, i would appreciate an answer in a text form not handwritten. thank you

Answer 1

1.

NAD+ and FAD are cofactors for many respiratory enzymes. They help in capturing the reducing energy from glucose. The reduced forms, NADH and FADH2 are used to establish proton gradient in the mitochondria which drive ATP synthesis via oxidative phosphorylation.

The reaction catalyzed by pyruvate dehydrogenase.

Pyruvate + CoASH + NAD+ -----------> Acetyl Co-A + NADH + H+ + CO2

The reaction catalyzed by succinate dehydrogenase.

Succinate + FAD -----------> Fumarate + FADH2

2.

Cellular respiration is less efficient than combustion of glucose.

Aerobic respiration of glucose releases (36 X 7.3) = 262.8 kcal/mol

Combustion of glucose releases -686 kcal/mol.

Efficiency of respiration = 262.8/686 =0.383 = 38.3%

The remaining energy is dissipated as heat.

3.

The energy stored in all the bonds of a molecule corresponds to its bond energy.

Glucose contains 5 C-C, 7 C-H, 7 C-O and 5 O-H bonds.

= (5 X 347 + 7 X 413 + 7 X 358 + 5 X 467)

= 9467 kJ

Bond energies can be calculated by quantifying energy released during chemical reactions (Number of bonds rearranged and the total amount of energy released/absorbed).