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