1 - Biological molecules

Question 1

Structure of cellulose

Answer 1

-Chain of beta glucose molecules joined by hydrogen bonds producing microfibrils providing rigid structure
- Large and insoluble

Question 2

Structure of starch

Answer 2

-Storage carbohydrate in plants
- Long, branched chains of alpha glucose molecules
- Insoluble so osmotically inactive
- Helical shape so forms compact store
- Large number of glucose molecules so abundant supply of respiratory substrate
- Too large to cross cell membrane so remains where formed

Question 3

Structure of glycogen

Answer 3

• Storage carbohydrate in animals cytoplasm
• Insoluble
• Osmotically inactive
• Branched chain of alpha glucose molecules but with free ends - large SA and hydrolysed rapidly to release glucose
• stored in large amounts in liver and muscle tissues

Question 4

How to test for reducing sugars

Answer 4

• Add Benedicts reagent then heat for 5 minutes
  -Blue to red

Question 5

Test for non reducing sugar (sucrose)

Answer 5

Add Benedicts reagent then heat
- Fresh sample add acid then heat to hydrolyse glycosidic bond releasing fructose and glucose
- Add alkali to neutralise acid
-Add benedicts reagent and heat
- Blue to red

Question 6

Test for starch

Answer 6

• Add few drops of iodine
• Yellow/orange to blue/black

Question 7

Test for proteins

Answer 7

• Few drops of copper sulphate
• Few drops of sodium hydroxide
• Blue to purple

Question 8

Test for lipids

Answer 8

• Add ethanol then add water then shake
• Clear to milky white emulsion

Question 9

How does ES complex lower Ea

Answer 9

-Changes shape of molecule which causes stress on the chemical bonds lowering the Ea needed for substrate to break apart

Question 10

What is a competitive inhibitor

Answer 10

• Inhibitor molecule with similar shape to substrate which prevents substrate from binding to active site
• Can be reduced by adding lots of substrate so sub is more likely to bind to enzyme

Question 11

What is a non - competitive inhibitor

Answer 11

• Attaches to allosteric site on enzymes away from active site
• hydrogen and ionic bonds break
  -Tertiary structure and active site shape change
• Substrate not complementary to active site

Question 12

What are the 6 functions of water

Answer 12

1- Metabolite
2 - Solvent
3 - Mass flow - can move as continuous stream
4 - Surface tension
5 - High latent heat of vaporisation - helps keep organisms cool
6 - High specific heat capacity - Buffers changes in temp