4. Biological Molecules

Question 1

Carbohydrates

Answer 1

Made from Carbon, Hydrogen and Oxygen

Simple sugars- Starch and Glycogen

Question 2

Fats and Oils

Answer 2

Carbon, hydrogen and Oxygen

Fatty Acids and glycerol - Fats and oils

Question 3

Proteins

Answer 3

Carbon, Hydrogen, Oxygen, Nitrogen and sometimes Sulphur

Amino acids - Proteins

Question 4

Test for Starch

Answer 4

Reagent: Iodine Solution

Process: Add a few drops of Iodine to the food sample

Results: Turns from brown to blue-black

Question 5

Test for Reducing Sugars

Answer 5

Reagent: Benedict’s Reagent

Process: Add reagent to food sample, shake and heat in water bath for max 10 minutes

Results: Will change from blue to brick red ppt

Question 6

Protein Test

Answer 6

Reagent: Biuret Reagent

Process: Add reagent to food sample and shake

Results: Changes from blue to purple

Question 7

Fat Test

Answer 7

Emulsion test

Add ethanol to food sample and put this in a test tube with equal amounts of water

Results: Milky-White ppt

Question 8

Vitamin C Test

Answer 8

Reagent: DCPIP

Process: Add food sample in a test tube of DCPIP

Results: Decolorisation of DCPIP (from blue to colourless)

Question 9

Structure of DNA

Answer 9

Chromosomes are made of a molecule called DNA
2 strands coiled together form a double Helix
Each strand contains bases
A matches T
C matches G