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Chemical reactions involve breaking and forming of chemical bonds. There are two main types of chemical reactions, namely anabolism and catabolism.
Anabolism
Reaction involves formation of complex substances from simpler substances. This process requires input of energy.
Eg Many glucose molecules join to form a complex large, insoluble molecule known as starch. glucose --> starch. Other examples include formation of glycogen, lipids and proteins.
Above: Glucose molecules join to form a linear molecule of starch.
Catabolism
Reaction involves the breakdown of complex substances into simple substances. The process releases energy.
•Egs of catabolic reactions include break down of large, complex food molecules eg starch into simple, soluble forms, eg maltose.
For example, a linear chain of starch is broken down to form maltose sugars.
Characteristics of Metabolism
•Metabolism occurs in a series of small reactions which make up a metabolic pathway.
•Metabolism occurs in small steps:
(1)Reactions that go in large steps generate a lot of heat that can kill cells.
(2)Substances that are partially broken down provide raw materials for other reactions.
(3)Small steps to a metabolic pathway increases the cell’s ability to control the products made.
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