Biological molecules - Paper 2

Question 2

What are carbohydrates made of?

Answer 2

starch (mainly in plants) / glycogen (mainly in plants), which are made up of long chains of simple sugars

Question 3

What are simple sugars?

Answer 3

• e.g glucose
• the chemical name for a simple sugar is a monosaccharide
• when 2 simple sugars join together they form a disaccharide
• when lots of simple sugars join together they form a polysaccharide
• examples of polysaccharides are starch and cellulose and glycogen

Question 4

What is the most common type of lipid found in the body?

Answer 4

Triacylglycerol
-made up of two different sub units called glycerin and fatty acids

Question 5

Draw a diagram of a triaglycerol

Answer 5

Include: -glycerol, fatty acids

Question 6

What are proteins?

Answer 6

• made up of long chains of amino acids
• there are 20 different types of amino acid and they can be joined together in different orders to make many different types of protein.

Question 7

What are enzymes?

Answer 7

• enzymes are biological catalysts
• they speed up chemical reactions in cells
• without enzymes, the reactions in cells would be too slow to support life
• some enzymes catalyse synthetic reactions (where large molecules are built-up from small molecules) e.g making glycogen from glucose (glucose synthase)
• other enzymes catalyse the breakdown reactions (splitting large molecules into smaller ones). E.g making glucose from glycogen (glycogen phosphorylase)
• enzymes are proteins: they are made up of long chains of amino acids which are folded into a specific shape

Question 8

What is the lock and key hypothesis?

Answer 8

• it suggests that the substrate fits into an enzyme molecule like a key fits into a lock
• the active site of the enzyme fits onto ( complimentary shape) to the substrate
• the enzyme weakens the bonds in the substrate, causing it to split and form the products
• the products of the reaction are released at the end, leaving the enzyme free to be used again

Question 9

What is a metabolic reaction?

Answer 9

The breaking down of a compound

Question 10

Why is the rate of reaction of an enzyme slow at low temperatures?

Answer 10

• the enzyme and substrate move slowly due to low kinetic energy
• this means there are less collisions per second, so they hook onto each other less often, so less enzyme-substrate complexes form

Question 11

Why does the rate of reaction of enzymes increase as temperature increases?

Answer 11

The rate increases as the temperature gets closer to the optimum temperature of the enzyme

Question 12

What happens to rate of reaction of enzymes at high temperatures and why?

Answer 12

• at temperatures above the optimum temperature, enzymes become denatured as their active site denatures and no longer fits onto the substrate
• this means less enzyme-substrate complexes can form.
• denatured means the enzyme is irreversibly damaged

Question 13

What is optimum pH?

Answer 13

• the certain pH needed by enzymes for them to work efficiently
• some enzymes work best in acidic conditions, other in alkaline conditions
• pH conditions which are too different from the optimum pH of the enzyme can change the enzyme’s active site shape