Question

How do chemical reactions play a role in energy transfer?

a) Energy from the breakdown of glucose and other molecules in animals is released as ATP, which transfer energy to other reactions.
b) Energy from the breakdown of glucose and other molecules in animals is released in the form of NADP, which transfers energy to other reactions.
c) Energy is released in the form of glucose from the breakdown of ATP molecules. These ATP molecules transfer energy from one reaction to other.
d) Energy is released in the form of water from the breakdown of glucose. These molecules transfer energy from one reaction to other.

Answer 1

Glucose and water are not the energy soures in animals. SO option (c) and (d) can be eliminated. NADP has to be present in the reduced form NADPH+ to be harvested by the mitochondria, which is used in the electron transport chain to produce ATP. Therefore option (b) can be opted out.

Breakdown of glucose (6-carbon) by the glycolytic cycle yields 2 molecules of pyruvate (3-carbon), 2 moleucles of NADH+ and 2 molecules of ATP. The pyruvate is oxidised to 2 molecules of acetyl-CoA which is used up in the TCA cycle to produce 8 molecules of NADH+, 2 molecules of FADH2, and 2 molecules of GTP. Other molecules are broken down to acetyl-coA, which is channelised to the TCA cycle again. All the reduced electron carriers like NADH+, FADH2, etc are oxidised in the inner mitochondrial membrane and the protons released to the intermembrane space to create an electrochemical gradient. This gradient is utilised by the ATP synthase to generate ATP molecules, which is transferred to other reactions as an energy source. Therefore option (a) is right.

Answer (a) Energy from the breakdown of glucose and other molecules in animals is released as ATP, which transfer energy to other reactions.