Biological molecules

Question 1

Carbohydrates

Answer 1

• Main respiratory substrate

- Structural roles - cell walls and membranes

Question 2

Lipids

Answer 2

• Found in cell membranes
• Used as respiratory substrates
• Many hormones are lipids

Question 3

Proteins

Answer 3

• Enzymes
• Hormones
• Cell membranes
• Components of blood

Question 4

Nucleic acid

Answer 4

• Genetic code

- Carry info used to synthesise proteins in cells

Question 5

What is a monomer

Answer 5

• A single unit

- A repeating monomer unit can form a polymer

Question 6

Give two examples of biological polymers

Answer 6

• Carbohydrates

- Lipids

Question 7

What is a condensation reaction

Answer 7

• Joining of a monomer by the removal of water to form dimers

Question 8

What is a hydrolysis reaction

Answer 8

• Separation of dimers to form 2 monomers by adding water back into the reaction

Question 9

Glucose, galactose and fructose all have the same formula of c6h12o6 but they are different sugars. Explain how

Answer 9

• They are isomers

Question 10

A molecule is a different shape from trehalose. Explain why

Answer 10

• The atoms are arranged differently

Question 11

Describe the difference between a glucose and b glucose

Answer 11

• The OH group in B is inverted to the top whereas the OH group in A is at the bottom

Question 12

Explain two ways in which the structure of glycogen and starch are related to their function

Answer 12

• They both form helix’s
• Compact as the coils are tight
• They are both storage molecules
• Branched to allow fast release of energy

Question 13

Explain two ways in which the structure of cellulose is related to its function

Answer 13

• It forms long, straight chains
• Hydrogen bonds hold the chains together
• Form strong layer of cellulose
• Structure makes them insoluble - not branched

Question 14

How would you test for starch

Answer 14

• Add iodine solution

- Solution turns brown to dark blue

Question 15

How would you test for reducing sugars

Answer 15

• Add benedicts solution

- Brick red/orange

Question 16

Describe how you could test a solution to show that it contains a non-reducing sugar

Answer 16

• Following a negative test for a reducing sugar
• Normally boil with acid
• Then neutralise with alkali
• Then repeat benedicts test

Question 17

The diagram shows the structure of glycerol and a fatty acid. Name the bond formed

Answer 17

• Ester bond

Question 18

Name the reaction that occurs when a triglyceride is formed when fatty acids and glycerol (1 mark)

Answer 18

• Condensation/esterification

Question 19

Describe the difference between a saturated and unsaturated fatty acid

Answer 19

• Saturated has only single bonds

- Unsaturated has double bonds

Question 20

Give the general name for a carbohydrate monomer (1)

Answer 20

• Monosaccharide

Question 21

In what type of reaction do monomers join together? (1)

Answer 21

• Condensation

Question 22

Name the bond that forms between beta glucose

Answer 22

• Glycosidic bond

Question 23

Name the helical polysaccharide that is a useful plant storage compound (1)

Answer 23

• Starch

Question 24

Give 2 reasons why starch is suitable for its function (2)

Answer 24

• Compact - more starch released when broken down

- Insoluble - won’t affect the water concentration in cells

Question 25

Some polysaccharides are branched. How does this change its properties? (1)

Answer 25

• Digested by enzymes quicker

- More soluble

Question 26

Explain how cellulose gives strength and support to plant cell walls. (1)

Answer 26

• Bonded together by hydrogen which holds layers together making strong cell walls