 |
| Energy Transfer and Energy Transformation |
|
| |
| Energy is the capacity to do work. All living organisms require energy for carrying on their vital metabolic activities. The primary source of energy for living system is solar radiation. The radiant energy of sunlight cannot be utilised directly by all living organisms. This ability rests only with the green plants. All the other organisms have to meet their energy requirement only through the green plants. |
| |
| Green plants represent the entry point for the flow of energy in the living system, which is always unidirectional. |
| |
| Energy that flows in the living system is called bio-energy and the study of changes in energy as it flows through a living system, is called bioenergetics. |
| |
| All energy conversions in the living system are governed by certain invariable principles called laws of thermodynamics, as in any physical system. |
| |
| There are two types of energy changes in the living system, namely |
| |
 Energy transformation |
| |
|
Energy transfer |
| |
| |
| |
 |
| |
| fig. 1.2 - Energy transfer and energy transformation |
| |
 |
| |
 |
| |
| ATP (adenosine triphosphate) is an energy rich compound having three phosphate group attached to a nucleoside of adenine (a nitrogen base), called adenosine (adenine + pentose sugar). Of the three phosphate groups, the terminal one has a weak linkage. This phosphate group can break spontaneously whenever ATP forms a complex with an enzyme. The breaking up of this bond releases chemical energy causing an immediate shift in the bond energy giving rise to adenosine diphosphate (ADP). |
| |
 |
| |
| ATP is therefore commonly described as 'energy currency of the cell'. |
| |
|
| It is a measure of the degree of disorder or randomness of a system. It corresponds to the amount of energy that is not available for work in a system. Loss of energy in the form of heat results in an increase in the entropy of a system. |
| |
| In the biological system, an increasing degree of entropy results in the death of a cell or an organism, unless energy is restored. Living organisms restore their lost energy either directly from sunlight (as in green plants) or from their food molecules (as in other organisms). |
| |
