paper 1 mistakes

Question 1

define in terms of genetic code:
universal
non-overlapping
(2)

Answer 1

• the same codon always codes for same amino acids
• adjacent codons dont overlap

Question 2

state 2 roles of helper T cell (2)

Answer 2

• stimulate B cells
• stimulate cytotoxic T cells
• stimulate phagocytes

Question 3

define species richness and index of diversity (2)

Answer 3

• number of species in a community
• relationship between number of species and number of individuals in each species

Question 4

explain 2 reasons why glucose uptake by muscle cells increases significantly during exercise (4)

Answer 4

• increased respiration
• to provide more ATP for muscle contraction
• concentration gradient for glucose
• glucose enters by facilitated diffusion

Question 5

dark stain used on chromosomes binds to some areas more than others making the chromosomes appear striped.

give 2 ways the structure of chromosome differs along its length to result in stain binding more in some areas (2)

Answer 5

• difference in histones
• difference in base sequences
• difference in supercoiling

Question 6

scientists collected bees using an ethical method.

suggest in each case 1 consideration to make sure their method :

• was ethical
• allowed them to identify accurately the species to which each bee belonged

Answer 6

• must not harm bee
• must allow close examination of bee

Question 7

formation of an enzyme substrate complex increases the rate of reaction.

explain how (2)

Answer 7

1. reduces activation energy
2. due to bending bonds

Question 8

scientists investigated an enzyme which converts ATP to ADP and Pi

in 1 experiment they added a sugar called lyxose and this increased the reaction rate.

lyxose binds to the enzyme. suggest how it increases the rate (3)

Answer 8

1. binding alters tertiary structure of enzyme
2. active site changes shape
3. more ESCs form

Question 9

scientists are making antivenom. they mix a mixture of venoms from different snakes of same species.

suggest why (2)

Answer 9

1. may be different forms of toxin/antigen
2. different antibodies are needed

Question 10

during vaccination each animal in initially injected with small volume of venom then 2 weeks later a larger volume.

use humoral immune response to explain why (3)

Answer 10

1. B cells specific to venom reproduce by mitosis
2. plasma cells and memory cells form
3. 2nd dose produces antibodies in higher concentration and quickly

Question 11

suggest how heat treatment may damage the phloem (2)

Answer 11

1. movement in phloem requires living cells
2. heat treatment damages living cells so transport in phloem through plants is only in untreated plants

Question 12

compare and contrast phospholipids and triglycerides (5)

Answer 12

• both have ester bonds
• both have glycerol
• both have C,H,O but phospholipid has P
• triglyceride non polar but phospholipid has hydrophilic and hydrophobic region
• triglyceride has 3 fatty acids, phospholipid has 2 fatty acids and phosphate head
• both are insoluble in water