12th Class Biology Origin of Life Energy Flow

Energy Flow

Category : 12th Class

(1) Energy Transformation : It is the phenomenon in which one form of energy is changed into another form of enrgy. e.g. in photosynthesis (anabolism), radiant (Kinetic) energy of sunlight is changed into chemical (potential) energy of glucose. All the living organisms depend upon this transformation.

(2) Energy Transfer : It involves the movement of energy from one source or area or substance to another in the same form. e.g. in cell respiration (catabolism), oxidative break down of glucose occurs inside the mitochondria of aerobic plants and animals.

The glucose is enzymatically catabolised by stepped breakdown into water and \[C{{O}_{2}}\] and about 686 kcal of energy is released per mole of glucose. A part of released energy is stored as chemical energy in high energy bonds of ATP (adenosine triphosphate) formed by phosphorylation of ADP.



Some examples of Energy transformation.

Type of Energy Transformation


 Chemical to electrical

Nerve cell

 Light to electrical

Retina of eye

 Chemical to osmotic


 Chemical to mechanical

Muscles and cilia

 Sound to electrical


 Chemical to light


 Chemical to heat


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