Chapter 1- Biological molecules

Question 1

Explain covalent bonding

Answer 1

Where atoms share a pair of electrons in their outer shells. The outer shell of both atoms are filled and a molecule is formed.

Question 2

Explain ionic bonding

Answer 2

ions with opposite charge attract to each other.
for example Na+ attracts to Cl- to form sodium chloride.

Question 3

Explain hydrogen bonding

Answer 3

• when electrons aren’t evenly distributed but spend more time in one position
• this makes this region more negatively charged than the rest of the molecule.
• a weak electrostatic bond is formed

Question 4

What are monomers

Answer 4

Individual molecules which can bond together to form a polymer

Question 5

What are polymers

Answer 5

• long chains of monomer sub-units.
• they are formed in a process called polymerisation
• glycosidic bonds from a condensation reaction

Question 6

Outline condensation reactions

Answer 6

• A molecule of water is formed
• glycosidic bond is formed
• e.g polysaccharides are formed from monosaccharide glucose is an example of condensation reaction.

Question 7

Outline hydrolysis reactions

Answer 7

• addition of water break the bonds that link sub-units
• i.e polymer gets hydrolysed into monomers
• e.g starch can be hydrolysed into glucose

Question 8

Definition of metabolism

Answer 8

All the chemical processes that take place in living organisms

Question 9

Describe the mole

Answer 9

• The SI unit for measuring the amount of a substance and is abbreviated to mol
  -One mol contains the same number of particles as there are in 12g of carbon-12 atoms
• 12g of carbon-12 atoms contains 6.022x10^23 also known as Avogadro constant.

Question 10

Define:
-monosaccharide
-disaccharide
-polysaccharide

Answer 10

• 1 single monomer
• 2 monomers joined in a condensation reaction
• a large amount of monomers combined by a condensation reaction.

Question 11

how many isomers does glucose have

Answer 11

2:
- alpha glucose
-beta glucose

Question 12

How to test for reducing sugars

Answer 12

• add benedicts reagent which is an alkaline solution of copper (II) sulfate
• when heated with benedicts reagent, if there’s a positive result, a insoluble red precipitate is formed.

Question 13

• glucose + glucose =
• glucose + fructose =
• glucose + galactose =

Answer 13

• maltose
• sucrose
• lactose

Question 14

Test for starch

Answer 14

• add iodine solution to a sample
• presence of starch is indicated by a blue-black coloration

Question 15

Describe starch

Answer 15

• polysaccharide
• found in form of small grains in many parts of plants
• made up of chains of alpha-glucose
• linked by glycosidic bonds in condensation reactions

Question 16

outline 3 features and 1 function of starch

Answer 16

ANY 3 FROM:

• insoluble so doesn’t affect water potential
• large so doesn’t diffuse out of cells
• compact so a lot can fit in a small place
• when hydrolysed it forms a-glucose which is both easily transported and readily used in respiration
• branched meaning glucose monomers are released very rapidly
  + main role is to act as energy storage

Question 17

In which organisms is glycogen found

Answer 17

Animals and bacteria but never in plants

Question 18

Structure and function of glycogen

Answer 18

very similar to starch but:
- has shorter chains
- is more highly branched
Functions include being a major carbohydrate storage product of animals. This helps for animals which have a higher metabolic rate as they would have a higher respiratory rate so require more energy.

Question 19

Structure / function of cellulose

Answer 19

• different from starch and glycogen because it is made from monomers of b-glucose
• has straight, unbranched chains which run parallel to each other
  Functions are:
• to add strength to a cell
• form rigidity to plant cell walls
  -prevents the cell from bursting as water enters into it by osmosis

Question 20

Properties of lipids

Answer 20

• contaibn: carbon, hydrogen and oxygen
• insoluble in water
• soluble in organic solvents such as alcohols and acetone

Question 21

What are the two main groups of lipids

Answer 21

• triglycerides
• phospholipids

Question 22

Roles of lipids

Answer 22

• source of lipids when oxidised

Question 23

Structure of an amino acid

Answer 23

• central carbon attached to 4 different chemical groups:
• amino group (NH2)
• carboxyl group (COOH)
• hydrogen atom (H)
• R group

Question 24

Describe the primary structure of proteins (polypeptides)

Answer 24

• through condensation reactions
• many AA monomers join through polymerisation
• resulting in many hundreds of AA’s called a polypeptide
• the sequence of AA forms the primary structure of proteins

Question 25

What are catalysts

Answer 25

catalysts alter the rate of a chemical reaction without undergoing permanent changes themselves

Question 26

What is the activation energy

Answer 26

the minimum amount of energy required to start a reaction

Question 27

Describe the induced fit model

Answer 27

• the active site forms as the enzyme and substrate interact ( enzyme-substrate complex) i.e the enzyme can mould itself around the substrate
• when these are bonded, it puts strain on the substrate molecule which in effect lowers the activation energy

Question 28

Name some factors affecting enzyme action

Answer 28

• temperature
• pH
• concentration

Question 29

Describe inhibitors

Answer 29

substances that directly or indirectly interfere with the functioning of the active site resulting in reduced activity

Question 30

Describe:
-Competitive inhibitors
- Non-competitive inhibitors

Answer 30

• bind to the active site of the enzyme
• bind to the enzyme at a place other than the active site