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biology 0610printed 45 · PDF 45
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Some of the Biological molecules are
Carbohydrates
Fats
Proteins
Carbohydrates
These molecules are made up of three elements:oxygen,carbon and hydrogen.
One molecule contain twice as many hydrogen as oxygen or carbon atoms
Examples of carbohydrates are starch, cellulose and sugars.
Glucose ( a carbohydrate) has a hexagonal shape. It is the way carbohydrates are
transported from one place to another in the body.
The glucose is not stored as it is in animals. It is first converted into a bigger molecule
known as glycogen by joining a lot of glucose together.
In plants glucose is stored in a different way. Plant stores them as starch.
Iodine test is carried out to check the presence of starch. If the starch is present then
the iodine solution turns blue black from brown.
Cellulose (a carbohydrate) made by linking up glucose in spiral shape is used to
plant cell walls
Presence of reducing sugars can be tested through Benedict's solution. Its color
originally is blue but gradually turns to green then yellow and at last orange red.
If the color is green then it means that the concentration of reducing sugars is less but
if the color is orange red then it means that the concentration of reducing sugars is
very high.
Fats and Oils
Also known as lipids
They also contain 3 elements: oxygen, carbon and hydrogen.
Fat molecules are made up of 2 kinds of smaller molecules: glycerol and fatty acids.
Each glycerol molecule is attached to 3 fatty acids.
Fats are used to make cell membrane.They are also used as energy stores and the
layer of fat beneath the skin plays the role of an insulating layer keeping the body
warm.
Presence of fats can be checked through fat emulsion test. Shake the sample with
ethanol so that if there is fat it dissolves in it.Now pour the ethanol solution into water.
If there are fats present then tiny droplets appear throughout the solution which gives
it a milky appearance.
Emulsion is a liquid containing 2 substances that don’t fully mix.