Biological Molecules

body type shi

list the chemical elements which make up

• carbohydrates

• fats

• proteins

• carbohydrates - Oxygen, Carbon, Hydrogen

• fats - Oxygen, Carbon, Hydrogen

• proteins - Oxygen, Carbon, Hydrogen, Nitrogen

State 2 roles of carbohydrates

• gives an immediate source of energy

• to form supporting structures

State 2 roles of fats

• long-term storage of energy

• provides insulation for the body to prevent heat loss

State 2 roles of proteins

• For growth and repair of cells

• synthesise of enzymes

Describe and carry out food tests for starch

Iodine test: add a drop of iodine to the food sample on a white tile. Presence of starch:blue-black. No starch: brown.

Describe and carry out food tests for fats

Ethanol test: add 2cm^3 of ethanol solution to 2cm^3 food sample that is in a dry test tube. shake the test tube. add water to the test tube and then shake it thoroughly. check if it remains clear:no fats. or white and cloudy: got fats.

Describe and carry out food tests for proteins

Biurets Test: take 2cm^3 of biurets solution and put it in a 2cm^3 liquid sample that is in a test tube. Shake the mixture. Then check if it remains blue: no proteins, if it changes to violet/purple got proteins.

Describe and carry out food tests for reducing sugars

Benedicts test: Take 2cm^3 of Benedicts solution and add it to 2cm^3 of liquid solution in a test tube. Shake the mixture thoroughly. Place the test tube in a boiling bath for 2 minutes and then check the results. Blue: no reducing sugars. Green-orange: few reducing sugars. Brick red: a lot of reducing sugars.

state that large molecules are synthesised from smaller basic units. (How CARBOHYDRATES,PROTEINS,FATS are formed)

cellulose, glycogen and starch from glucose and glucose from carbohydrates

amino acids from polypeptides and polypeptides from proteins

lipids from fatty acids and glycerol