2. An eyepiece graticule has a scale with 100 divisions. A stage micrometer has a scale with 50 divisions, each of which is 0.040 mm apart.

Using a ×40 objective lens, the whole length of this stage micrometer scale lines up with 15 divisions of the eyepiece graticule.

What is the actual length of the 100 division scale of the eyepiece graticule?

3. A prokaryotic cell which is 1 μm in diameter, is magnified 50 000 times in an electron micrograph.

What is the diameter of the cell in the electron micrograph?

4. A scientist carried out an experiment to separate cell structures in animal cells.

The cells were broken open to release the cell structures.

This extract was filtered into a centrifuge tube and then spun in a centrifuge. The heaviest cell structure sank to the bottom forming pellet 1, as shown in the diagram.

The liquid above pellet 1 was poured into a clean centrifuge tube and spun in the centrifuge at a higher speed to separate the next heaviest cell structure. This cell structure sank to the bottom, forming pellet 2.

This procedure was repeated twice more to obtain pellet 3 and pellet 4, each containing a single type of cell structure.

Which row shows the order in which the cell structures were collected?

5. Radioactively-labelled nucleotides are introduced into a cell.

In which cell structures will the radioactivity first become concentrated?

6. What is the general formula for amylose?

7. The diagram shows relationships between some important molecules and bonds.

What is represented by circles numbered 1, 2 and 3?

8. In unsaturated lipid molecules, where are double bonds located?

9. Phospholipids and triglycerides are important biological molecules.

Which properties are correct for these molecules?

10. The diagrams show two arrangements of amino acids in a protein.

Which row correctly names the bonds at S or T?

11. Students were asked to highlight only the R groups of two ring-shaped amino acids.

Which pair of diagrams are correct for both amino acids?

12. Which words from the table correctly complete the paragraph about enzymes?

When the pH of an environment is decreased below the optimum pH of an enzyme, ....1...... bonds between adjacent ......2....... groups, holding the ......3...... structure, are disrupted.

13. The effect of substrate concentration on an enzyme-catalysed reaction was measured in three different conditions:

● with no inhibitor

● with a competitive inhibitor

● with a non-competitive inhibitor.

The graph shows the results.

Which statement is correct?

14. Which statements about the cell surface membrane are correct?

1 Channel proteins allow water soluble ions and molecules across the membrane.

2 Glucose can pass into the cell via carrier proteins.

3 Oxygen passes freely through the membrane as it is soluble in lipids.

4 Some glycoproteins act as antigens.

15. Which of these features increase the efficiency of ion uptake by a root hair cell?

1 many mitochondria in the cell

2 high concentration of ions in the vacuole

3 protein carriers in the cell surface membrane

16. What can increase the fluidity of the cell surface membrane at low temperatures?

1 double bonds between carbon atoms in the fatty acid chains

2 cholesterol

3 fatty acids having shorter chains

17. The diagrams show the shape and size of two types of cell.

Which statement is correct about the palisade cell and epithelial cell shown in the diagrams?

18. A student observed the cells in the growing region (meristem) of an onion root and obtained the

data shown.

Which percentage of cells contains chromosomes that appear as two chromatids?

19. Which of these events are part of mitosis?

1 interphase

2 telophase

3 cytokinesis

20. During which phase of the cell cycle does DNA replication take place?

21. Which row is correct for guanine?

key: √= correct, x= incorrect

22. Meselsohn and Stahl investigated DNA in bacteria. They grew bacteria in a medium with only heavy nitrogen, ¹⁵N, until all of the bacterial DNA was heavy.

These bacteria were moved from a heavy nitrogen medium and cultured in a medium with only

light nitrogen, ¹⁴N.

A sample of bacteria was collected from the first generation in the medium containing light nitrogen and their DNA was analysed.

Hybrid DNA contains both heavy and light DNA.

Which row shows the percentage of heavy DNA strands and the percentage of hybrid DNA molecules in the first generation produced in the medium containing light nitrogen?

23. Which is the correct DNA triplet on the original DNA template that codes for the amino acid

histidine (His)?

24. The photomicrograph shows tissues in a stained transverse section of a plant stem.

Students are asked to draw four adjacent xylem vessel elements.

Which drawing, all drawn to the same scale, is correct?

25. What is a function of the hairs (trichomes) on xerophytic leaves?

26. Which features of companion cells are essential to their function?

1 They are connected by plasmadesmata to the sieve tube elements.

2 They have a thinner cell wall than a sieve tube element.

3 They contain a nucleus and mitochondria.

27. The photomicrograph shows a human blood smear.

Which row identifies the labelled cells?

28. The diagram shows the changes in electrical activity in the heart muscle during one cardiac cycle. This is called an electrocardiograph (ECG).

Which electrocardiogram shows a rate of 75 beats per minute?

29. Which effect could be due to a reduced concentration of carbonic anhydrase?

30. Which statement correctly compares blood plasma and tissue fluid in a healthy person?

31. The diagram shows three features found in tissues of the gas exchange system.

Which tubes of the gas exchange system could be represented at position P in the diagram?

key: √= yes, x= no

32. The diagram shows a magnified section of part of the lungs containing specialised tissues.

Which row is correct for structures labelled 1 to 6?

33. A short-term effect of smoking is a decreased blood supply to the fingers and toes.

Which component of cigarette smoke causes this effect?

34. The symptoms of two diseases are listed.

Which row identifies diseases 1 and 2?

35. Which statements about a non-infectious disease may be correct?

1 It can result from a mutation.

2 It can be transmitted by an insect vector.

3 It can be transmitted from mother to child.

36. The diagram shows one way of testing the effect of an antibiotic on bacteria.

37. Some animals have genes that code for small peptides called cathelicidins. These peptides kill a wide range of bacteria by attaching to lipids in bacterial membranes, so weakening or disrupting them.

Scientists have produced a synthetic version of the cathelicidin that kills bacteria that are resistant to a number of antibiotics such as tetracycline.

Which pair of statements explain how this synthetic cathelicidin might help with the problem of antibiotic resistance?

1 It is synthetic so bacteria can never become resistant to it.

2 It could be used instead of tetracycline, allowing tetracycline resistance to be reduced.

3 The only way a bacterium could develop resistance to it is by altering all the lipids in its membranes.

4 It could be used to kill multidrug-resistant strains of bacteria for which there is no effective antibiotic.

38. Hybridomas are used as a basis for the production of large numbers of monoclonal antibodies.

Which statement describes how hybridomas are made?

39. Which statement about the properties of the antigen binding sites in antibody molecules is

correct?

40. The statements describe ways in which different types of monoclonal antibodies can work.

1 binding to proteins on cell surfaces and triggering the immune system

2 blocking molecules on cell surfaces that inhibit T-cells

3 blocking cell signalling receptors that trigger cell division

4 blocking cell signalling receptors that trigger the immune response

Which types of monoclonal antibody could be used to treat cancer?