Paper 1 (topics 1–4)

Starch is a polymer. Name its monomer and the bond formed between monomers.

Explain how the structure of cellulose is related to its function in plant cell walls.

Describe a biochemical test to show that a solution contains a non-reducing sugar but no reducing sugar.

Describe how a triglyceride is formed.

Explain how the structure of phospholipids allows them to form a bilayer in cell membranes.

Describe the emulsion test for lipids.

Describe the structure of a DNA molecule.

Bacteria were grown on a medium containing heavy nitrogen (¹⁵N), then transferred to light nitrogen (¹⁴N). DNA was extracted and centrifuged (data are illustrative, written for this paper).

Generation in ¹⁴N	DNA bands
0	100% heavy
1	100% intermediate
2	50% intermediate, 50% light

Explain how these results support semi-conservative replication.

Describe the role of DNA polymerase in DNA replication.

Give two ways in which ATP is suited to being the immediate energy source in cells.

Explain two properties of water that are important to living organisms.

Describe the role of sodium ions in the absorption of glucose in the ileum.

Describe the roles of organelles in producing and secreting an extracellular enzyme.

In a drawing, a cell is 4.5 cm long. Its actual length is 15 µm. Calculate the magnification.

Describe what happens during anaphase of mitosis.

A drug was tested on cancer cells. The mitotic index fell from 28% to 9% (data are illustrative, written for this paper). Explain how this drug could slow tumour growth and suggest one disadvantage of using it.

A cube-shaped cell has sides of 2 cm. Calculate its surface area to volume ratio.

Explain why large multicellular organisms need specialised exchange surfaces and transport systems.

Describe the cohesion–tension theory of water movement in xylem.

In a potometer, an air bubble moved 24 mm in 5 minutes along a capillary tube of radius 0.5 mm. Calculate the rate of water uptake in mm³ min⁻¹. (Volume = πr²l)

Describe the mass flow hypothesis for translocation in phloem.

Give two differences between DNA in prokaryotic cells and DNA in the nucleus of eukaryotic cells.

Explain what is meant by introns and exons.

Explain why comparing the amino acid sequences of a protein can show relationships between species more reliably than comparing observable features.

Two populations of a snail had mean shell lengths of 21 mm (SD 1.2) and 24 mm (SD 3.5) (data are illustrative, written for this paper). Compare the variation in the populations and explain what the standard deviations show.

Describe the roles of T helper cells in the immune response.

Explain how monoclonal antibodies are used in a pregnancy test.

Give two differences between facilitated diffusion and active transport.

Cyanide stops respiration. Explain the effect of cyanide on the uptake of mineral ions by root hair cells.

Explain how the structure of the alveoli is adapted for efficient gas exchange.

A person with emphysema has a forced expiratory volume in 1 second (FEV₁) of 1.6 dm³ compared with a healthy value of 3.8 dm³ (data are illustrative, written for this paper). Calculate the percentage reduction and explain why it occurs.

Describe how proteins are digested in the human gut.

Explain how amino acids are absorbed from the ileum into the blood.

Describe and explain how the heart and blood vessels deliver absorbed amino acids from the ileum to working muscle cells.