4. Biological molecules

Question 1

chemical elements that make up:
carbohydrates, fats and proteins

Answer 1

Carbohydrates, fats- CHO
Protein- C,H,O,N,S

Question 2

large molecules are made from smaller molecules- carbohydrates, protein, fats and oil

Answer 2

starch, glycogen and cellulose from glucose

proteins from amino acids

fats and oils from fatty acids and glycerol

Question 3

food test- starch, glucose, protein, vitamin C, fats and oils

Answer 3

iodine solution test for starch- drops of it to food, yellow-brown to blue-black

Benedict’s solution test for reducing sugars- in test tube in water bath at 80 for 5 minutes. blue to red

biuret test for proteins- drops of it to food, blue to purple

ethanol emulsion test for fats and oils- put ethanol in food so it dissolves, put it in water in test tube. colourless to cloudy emulsion

DCPIP test for vitamin C- 1cm of dcpip in small amount of food, disappears- blue to colourless

Question 4

structure of a DNA molecule

Answer 4

(a) two strands coiled together to form a double helix

(b) each strand contains chemicals called bases

(c) bonds between pairs of bases hold the strands together

(d) the bases always pair up in the same way: A with T, and C with G