Biological molecules:
Water:
Water is needed as a solvent in chemical reactions
Doesn’t let our cells dry out hence keeping living organisms alive
Transport medium
Specific heat capacity
Medium for chemical reactions
Transpiration
Carbohydrates:
Made up of 3 elements C, H, O (hydrogen is double when
compared to carbon and oxygen atoms)
2 forms sugar and starch
Sugar is a very simple carbohydrate which is divided into further
groups called simple sugars (monosaccharide) which are very
small molecules and taste sweet and dissolve in water
The other type of sugar is a more complex one and is known as a
disaccharide and dissolves in water and tastes sweet too.
Starch can sometimes also come under the ‘Sugars’ it is formed
when lots of simple sugars join and become a large molecule
called a polysaccharide. Starts is insoluble and doesn’t taste
sweet.
Bond between carbohydrates is glycosidic bond
Glucose is used to release energy in animals and plants by
respiration
Cellulose (polysaccharide) is used to give plant cells their structure
as cellulose fibers are very strong.
Test for carbohydrates:
The test for a reducing sugar
1) Add benedicts solution to the food sample
2) Heat it in a water bath
3) Positive test will show color change from blue-> green-> yellow->
orange-> brick read
The test for starch:
1) Add iodine on food sample
2) Positive test will show colour change from orange-brown to blueblack
Proteins:
Contains C,H,O,N,S
Used for making new cells (for growing and repairing old damages
cells)
Makes antibodies (kills bacteria and viruses)
Enzymes are also proteins
Test for proteins:
1) Add water to food sample
2) Add dilute copper sulfate
3) Add dilute potassium hydroxide solution
4) Observe color changes
5) Positive test shows color change from Blue to purple/violet
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