Question

explain the concept of energy coupling and role of ATP in energy coupling

Answer 1

The vital processes occuring in the body such as muscular contraction, nerve impulse conduction, active transport, etc. obtain energy by energy coupling reactions.

Within a living cell, biomolecules are constantly being synthesized and transformed into some other biomolecules. these synthesis and transformation constantly occur through enzyme catalyzed chemical reactions. Together all the interconnected chemical reactions occuring within a cell are called metabolism.

Each of the chemical reactions results in the transformation of chemical compounds involved in this process and they are known as metabolites.

Majorly the metabolic reactions are linked to one another, transforming one chemical through a series of steps into another.These inter-linked series of chemical reactions are called metabolic pathways.

Metabolic pathways fall under two categories namely,

1. Anabolic pathway: Anabolic pathways involves synthetic reactions that build up substances and consume energy i.e. endergonic in nature. The process is termed as anabolism.

2. Catabolic pathway: Catabolic pathways involve oxidative breakdown of larger molecules into smaller simpler molecules leading to release of energy i.e. exergonic in nature. The process is termed as catabolism.

Catabolism and anabolism processes combine to constitute metabolism.

CONCEPT OF ENERGY COUPLING:

For coupling an endergonic and exergonic process a compound of high energy potential is synthesized in the exergonic reaction and incorporated into the endergonic reaction hence, transfering energy from the exergonic to the endogonic process. in the living cell, the principle high energy intermediate or carrier compound is adenosine triphosphate (ATP). It acts as a donor of high energy phosphate.

ROLE OF ATP IN ENERGY COUPLING:

ATP generation is driven by catabolic reactions (ADP + Pi conversion to ATP) whereas the ATP, once produced, is used to drive forward anabolic reactions ( ATP conversion to ADP + Pi)

Hence an ATP/ADP cycle connects those processes that generate Pi to those processes that utilize Pi continuously consuming and regenerating ATP.