2.1.4 Biology - Carbohydrates - Energy Storage

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Energy and storage:

Glucose molecules contain a large no. of bonds that can be broken to form simpler molecules. The breaking of glucose into simpler molecules of water and carbon dioxide in respiration releases energy. The energy can be used to make ATP (the molecule that holds small ‘packets’ of energy for use in cell processes).


Respiration is written as:

Glucose + oxygenàcarbon dioxide + water + energy that is used to form ATP


The breaking down of glucose in living organisms takes place in a series of many steps. Each step is driven by a specific enzyme. In order to be able to use glucose in respiration, an organism must have enzymes that can specifically break the glucose molecule.


Animals and plants have enzymes that break α-glucose only. Plant and animal enzymes cannot break down β-glucose because of its different arrangement of the H and OH at C1 (Carbon 1). This is because enzyme function is based on complimentary shape.  The overall shape of α-glucose is different from that of β-glucose. This means that α-glucose can be respired, β-glucose cannot.


Carbohydrate polymers- stores of potential energy:

Two α-glucose molecules bonded together form a disaccharide called maltose. The same condensation reaction can be carried out over and over again to join glucose molecules together, so forming a molecule called amylose. Amylose can consist of many thousands of glucose molecules bonded together. The glycosidic bond between all the glucose subunits occurs between carbon no. 1 of one molecule and carbon no. 4 of the next; so it is often called a 1, 4-glycosidic bond.

The long chains of amylose coil


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