2022 paper 1

Question 1

Describe the structure and function of the nucleus.

Answer 1

Nuclear envelope and pores
2. Chromosomes/chromatin
3. Nucleolus/nucleoli;
4. (Holds/stores) genetic information/material
for polypeptides (production)
5. DNA replication (occurs);
6. Production of mRNA/tRNA
Transcription (occurs);
7. Production of rRNA/ribosomes;

Question 2

Name the main polymer that forms the following cell walls.
[1 mark]
Plant cell wall
Fungal cell wall

Answer 2

cellulose
chitin

Question 3

Suggest one reason the scientists used biomass instead of the number of individuals
of each plant species when collecting data to measure diversity.

Answer 3

Individual organisms could not be identified/separated
Too small/numerous to count individuals
Too time consuming;

Question 4

Explain how the use of antibiotics has led to antibiotic-resistant strains of bacteria
becoming a common cause of infection acquired when in hospital.

Answer 4

(Some bacteria have) alleles
for resistance;
Resistant bacteria
survive/reproduce;
(So) high frequency of
resistance allele (in bacterial
population);

Question 5

Describe how the scientists could use aseptic techniques to transfer 0.3 cm3 of C. difficile in liquid culture from a bottle onto an agar plate.

Answer 5

Wash hands with soap
OR
Disinfect surfaces;
2. Use sterile pipette/syringe (to
transfer bacteria);
3. (Remove bottle lid and) flame
neck of bottle;
4. Lift lid of (agar) plate at an
angle;
5. Work close to upward air
movement;
6. Use sterile spreader;
7. Place pipette/spreader into
disinfectant (immediately after

Question 6

Use Figure 2 to evaluate whether more trehalose in the diet could be a factor in the
increased number of antibiotic-resistant C. difficile infections.

Answer 6

Resistant bacteria grow faster with trehalose;
2. (So) resistant bacteria (likely to) increase in
frequency in the population/people;
3. Resistant bacteria (likely to) outcompete
non-resistant bacteria;
Against
4. In laboratory not in people;
5. Other disaccharides (in the diet) might affect
bacteria;
6. Other bacterial species (in the body) might
affect bacteria;
7. No stats test to see if difference/increase is
significant;

Question 7

Give two features of all prokaryotic cells that are not features of eukaryotic cells

Answer 7

(Single,) circular/loop DNA (in cytoplasm)
OR
DNA free in cytoplasm
OR
DNA not associated with proteins/histones
OR
Murein/peptidoglycan (in) cell wall;

Question 8

This AP has a secondary structure in a helical shape.
Tick () the box to show which type of bond maintains the helical structure of the
polypeptide.

Answer 8

Hydrogen b

Question 9

Suggest how these properties of v APs allow them to become positioned across the
membrane (as shown in Figure 3) and make a channel through which ions can pass.
[2 marks]

Answer 9

Hydrophobic side next to/in/face fatty
acids/tails
OR
Hydrophobic side next to/in/face
hydrophobic (part of) phospholipid/bilayer;
2. Hydrophilic sides allow ion movement
through membrane
OR
Hydrophilic sides form a channel;