2023 paper 1

Question 1

Give the three structural features found in all virus particles and describe the function of one of these features. 2 marks

Answer 1

RNA, capsid and attachment protein
Capsid protects the genetic material
Attachment proteins bind to receptors on host cells

Question 2

Explain why viruses are described as acellular and non-living.2 marks

Answer 2

Acellular- no cell(-surface) membrane /Not made of cells
Non-living- have no metabolism/
Cannot independently move/respire/replicate/
excrete/ Have no nutrition

Question 3

Give one reason why antibiotics are not effective against viruses. 1 mark

Answer 3

Do not have bacterial structures/enzymes
OR
Do not have metabolic processes
OR
Do not have a cell wall/murein;

Question 4

Chitin has a similar structure to cellulose.
Use Figure 1 to describe three ways the structure of chitin is similar to the structure
of cellulose. 3 marks

Answer 4

Alternate monomers/glucoses are flipped by 180 degrees
Joined by) glycosidic bonds;
Forms straight/linear/unbranched (chains/molecules);

Question 5

Explain the importance of one adaptation of the gas exchange surface in the tracheal
system of an insect. 2 marks

Answer 5

-Tracheole wall is thin so rapid diffusion into cells
OR
(So) short diffusion pathway/distance
-Tracheoles enter/supply tissues/muscle fibres
So diffusion direct into cells

Question 6

Explain the importance of the xylem being kept open as a continuous tube. 3 marks

Answer 6

1.Allows unbroken water column OR So no barrier to water movement
2. Cohesion from H bonds between (all) water molecules
OR Cohesion from (polar) attraction between (all)
water molecules
3. Evaporation/transpiration creates tension (in column)
OR
Water moves from xylem (into cells) creates tension OR
(To) pull up water creates tension (in xylem);

Question 7

Describe two functions of the Golgi apparatus in a eukaryotic cell. 2 marks

Answer 7

Modify/package/transport proteins
OR
Make/transport glycoproteins;
Modify/package/transport lipids
OR
Make/transport glycolipids;
Forms/releases
vesicles/lysosomes;

Question 8

In Africa today, most of the human population are resistant to malaria caused by P. vivax.
Use your knowledge of natural selection to explain why this resistance is so common
in Africa. 4 marks

Answer 8

Mutation produced allele;
Those with allele/resistance less likely to/do not get malaria/P vivax
Those with allele/resistance survive malaria/P vivax;
So more likely to reproduce and pass on the allele;
Over generations) allele frequency increases

Question 9

The toxins damage the cells lining the ileum, causing them to lose their microvilli.
The damage to the cells reduces the absorption of the products of digestion and
reduces the absorption of water, resulting in diarrhoea.
Explain why the damage to the cells lining the ileum reduces absorption of the
products of digestion and why this reduces absorption of water. 4 marks

Answer 9

Reduced surface area
Fewer co transport/carrier/channel proteins;
Decreases water potential in ileum/lumen
Increases water potential in cells
So water moves out of cells/into ileum by osmosis
(So) less/no water moves into cells/out of ileum by osmosis