Complete note covering all aspects required for Cambridge O Levels Biology, Unit 4 Biological Molecules. Includes detailed explanations, clear tables and diagrams to help you ace your exams.
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Extra Note;
Carbon is an element present in almost all biological molecules.
Carbon atoms can join together forming chains or ring structures (Known as
macromolecules), often constructed of repeating subunits (Monomers).
Other elements that are always present are Oxygen and Hydrogen whereas Nitrogen can be
found in some cases.
When macromolecules are made of long chains of monomers held together by chemical
bonds, they are also called as polymers. (Ex; polysaccharides, proteins, and nucleic acid.)
1. Carbohydrates
They are simple, soluble sugars (Ex; glucose) or complex material like starch.
The simplest kind of carbohydrate are the simple sugars or monosaccharides.
Carbohydrates are:
A major source of energy in our diet.
Composed of Carbon, Hydrogen and Oxygen. (CHO) in the ratio 1C : 2H : 1O
Also called as Saccharides, meaning
sugars.
Is mainly produced by photosynthesis
in plants.
Often soluble in water.
Usually end in ‘ose’ (ex; glucose)
Sugars with single carbon ring are called ‘Monosaccharides’.
Sugars with two carbon rings are called as ‘Disaccharides’.
These monosaccharides and disaccharides are readily soluble in water.
When many glucose molecules join, it forms a ‘Polysaccharide’ which are insoluble in water.
(Ex; Starch, Cellulose which is made up of many glucose molecules ringed together). Most
polysaccharides are insoluble and do not taste sweet.
, 2. Lipids
Fats are semisolid or solid while oils are liquids at room temperature.
Lipids are organic compounds made up of Carbon, Hydrogen and Oxygen. (CHO)
A fat molecule consists of 2 parts; A glycerol backbone and 3 fatty acid tails.
Excess fat consumption causes the formation of “Plaque” in arteries.
The plaques are formed with the combination lipids/cholesterol with proteins (LDL).
Although the liver produces LDL, there is evidence to suggest that a high intake of animal
facts help to raise the level of LDL in the blood.
Most animal fats start formed from saturated fatty acids. While plant oils are formed from
unsaturated fatty acids, (Polyunsaturated) and are thought less likely to cause fatty plaques
in arteries.
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