Revision Questions for Units 1 and 2

UNIT 1
3.1.1
1. Name three types of pathogen.
2. Where do pathogenic organisms penetrate the body?
3. How do pathogens cause disease?
4. Give three aspects of lifestyle that can adversely affect human health.
5. What specific risk factors are associated with cancer?
6. What specific risk factors are associated with CHD?
7. What does CHD stand for, anyway?
8. What changes in lifestyle may reduce the risk of contracting these conditions?
9. What is the difference between a correlation and a causal relationship?
10. How may risk be quantified?

3.1.2
1. Sketch a diagram of the gross structure of the human digestive system.
2. Add the salivary glands and the pancreas to your diagram.
3. What happens during digestion?
4. Why is digestion necessary for almost all types of food?
5. Draw the general structure of an amino acid.
6. Draw two amino acids and show how a peptide bond forms between them.
7. What is the general name for this type of reaction?
8. Draw a dipeptide and show how the bond between them is broken during digestion.
9. What is the general name for this type of reaction?
10. Explain the primary, secondary and tertiary structure of a protein.
11. What is the key factor in the relationship between the structure of a protein and its function?
12. Describe in detail how you could carry out the Biuret test for protein.
13. What type of molecule are enzymes?
14. Explain, using the concept of activation energy, how enzymes catalyse reactions.
15. Describe the lock and key model of enzyme action.
16. Describe how the induced fit model of enzyme action differs from the lock and key model.
17. Which is the better model for enzyme activity, and why?
18. How do changes in temperature affect the rate of an enzyme catalysed reaction?
19. Explain why changes in temperature produce the effects you have described.
20. How do changes in pH affect the rate of an enzyme reaction?
21. Explain the differences between a competitive and a non-competitive inhibitor.
22. How does changing the substrate concentration affect the rate of an enzyme reaction?
23. Explain your answer to q21 in terms of active site availability.
24. Draw a diagram to show the basic structure of α-glucose.
25. Draw another diagram to show how α-glucose polymerises to form starch.
26. Name the bond formed between two molecules of α-glucose when they combine in this way.
27. What is a monosaccharide?
28. Name the disaccharide formed by the condensation of two α-glucose molecules.
29. Name the disaccharide formed from one molecule of glucose and one of fructose.
30. Which monosaccharides form a molecule of lactose?
31. Name the enzymes that hydrolyse lactose, sucrose and starch
32. Give the exact location in the digestive system of each of the enzymes you have named.
33. Describe in detail how you would carry out Benedict’s test to confirm a non-reducing sugar.
 34. Describe in detail how you would show that a compound contains starch.

3.1.3
1. Name the structures visible in a cell from the small intestine using an optical microscope.
2. Sketch a eukaryotic cell, including the structures visible using a TEM
3. What is a TEM? How is it different from a SEM?
4. Give some of the limitations of electron microscopy.
5. Explain carefully the difference between resolution and magnification.
6. How would you separate the individual components of a eukaryotic cell?
7. Explain how a triglyceride is formed from glycerol and fatty acids.
8. How may the R groups of the fatty acids differ?
9. How is the structure of a triglyceride different to that of a phospholipid?
10. Describe carefully how you would test a substance for the presence of lipid.
11. Describe how proteins, carbohydrates and lipids are arranged in the plasma membrane.
12. Give the functions of each of the following cell organelles:
Plasma membrane, microvilli, nucleus, mitochondria, lysosomes, ribosomes, endoplasmic
reticulum, Golgi apparatus.
13. Give a clear definition of diffusion.
14. Explain why surface area, difference in concentration and thickness of exchange surface
affect the rate of diffusion.
15. How does facilitated diffusion differ from simple diffusion?
16. Why is osmosis sometimes referred to as a special case of diffusion?
17. What is the meaning of the term isotonic?
18. Explain how active transport moves substances up a concentration gradient. Include the
roles of transport proteins and respiration.
19. Describe how the products of carbohydrate digestion are absorbed. Include the roles of
diffusion, active transport and co-transport.
20. Which taxonomic group does the Cholera bacterium fit into?
21. Sketch and label a typical prokaryotic cell.
22. How does the DNA of a prokaryote differ from the DNA of a eukaryote?
23. What advantage does the slime capsule give the cholera bacterium?
24. Explain why a person infected with the cholera bacterium produces a large quantity of very
watery diarrhoea.
25. What is ORS?
26. How does an ORS help to reduce the symptoms of cholera?
27. Explain two of the ethical issues that may arise when trialling improved ORS on humans.

3.1.4
28. Sketch a diagram of the human gas exchange system to show trachea, bronchi, bronchioles,
alveoli and lungs.
29. Explain how the alveolar epithelium is specifically adapted to ensure efficient gas exchange.
30. Describe how gases are exchanged between the blood and the air in the alveoli.
31. How is pulmonary ventilation calculated?
32. Explain how the ribcage and diaphragm cause air to move in and out of the lungs.
33. Describe the cause, symptoms, method of transmission and possible cure for pulmonary
tuberculosis.
34. Explain how each of the following causes its effects on lung function: fibrosis, asthma,
emphysema.
35. State the specific risk factors for the lung diseases given above.
 36. What effect does cigarette smoking have on the incidence of lung disease?
37. How does pollution affect the incidence of lung disease?
38. What is the difference between a correlation and a causal relationship?
3.1.5
39. Sketch a diagram to show the gross structure of the human heart. Label all blood vessels.
40. Explain in detail how the pressure changes that move blood through and out of the heart are
brought about during a single cardiac cycle.
41. Explain the roles of the different valves found in the heart.
42. What does the term “myogenic” mean?
43. Describe how electrical impulses are transmitted through the heart during the cardiac cycle.
44. Explain the importance of the following: the short time lag between the impulse at the SAN
and at the AVN; the ventricles contracting from the base upwards; two separate nerves
ending at the SAN.
45. How would you calculate cardiac output?
46. What is atheroma?
47. Explain the link between atheroma and aneurism and thrombosis.
48. What is myocardial infarction?
49. How do diet, blood cholesterol levels, cigarette smoking and high blood pressure each affect
the risk factors for CHD?

3.1.6
50. Describe how phagocytes destroy pathogens.
51. What is an antigen?
52. What is an antibody?
53. Describe the structure of an antibody.
54. Explain how antigen-antibody complexes are formed
55. What is the humoral immunological response?
56. Which type of blood cells carry out the humoral response? Describe briefly how this occurs.
57. What type of response is carried out by T-lymphocytes?
58. Describe the roles of plasma cells and memory cells in the immune response.
59. How does antibody production during a second infection differ from that during a first
infection? Explain why this difference occurs.
60. Explain why it is so difficult to produce a vaccine against some illnesses, such as influenza.
61. Explain why monoclonal antibodies are so useful in the targeting of specific substances and
cells.
62. Explain the role of the scientific community in validating new knowledge.
63. What ethical issues may arise in the use of vaccines and monoclonal antibodies?
 UNIT 2
3.2.1
1. Define variation.
2. When investigating variation, why does sampling need to be random?
3. Explain the contribution of chance to differences between samples.
4. What is a mean value? How is it calculated? Why is it important?
5. What is standard deviation? Why is it a better measure of variation than the range of values?
6. Explain how variation between two individuals of the same species may arise.

3.2.2
7. Describe in detail the structure of a molecule of DNA and explain how this enables it to act as
a stable, information-carrying molecule.
8. What is a gene locus?
9. Define a gene.
10. How do genes determine the nature and development of organisms?
11. Explain the link between the bases on the DNA and the primary structure of a protein.
12. What are introns?
13. Describe three differences between prokaryotic DNA and eukaryotic DNA.
14. What is meiosis?
15. When are chromosomes said to be homologous?
16. Explain how meiosis produces haploid cells.
17. What happens during independent assortment?
18. Explain why gametes are genetically unique.

3.2.3
19. Explain how variation between organisms can be defined in terms of DNA.
20. Explain the effect of each of the following on genetic diversity: selective breeding; the founder
effect; genetic bottlenecks.
21. Outline the ethical issues involved in the selection of domesticated animals. Refer to at least
one specific example.

3.2.4
22. What is haemoglobin, what is its function, and where is it found?
23. Describe the behaviour of haemoglobin as it associates with oxygen.
24. Sketch an oxygen dissociation curve, and explain the factors that may affect its shape.
25. What effect does carbon dioxide have on the dissociation curve of haemoglobin?
26. How do the properties of the haemoglobin of an organism relate to the environment in which
that organism lives?
27. Draw the structure of a molecule of β-glucose.
28. Explain how the structure of β-glucose differs from that of α-glucose.
29. Draw a diagram to show how a glycosidic bond forms between two molecules of β-glucose.
30. What is the name of the polymer formed by the condensation of a large number of β-glucose
molecules?
31. State where this molecule is commonly found.
32. The structure of polysaccharides is closely related to the function of the molecule. Explain how
the structures of starch, glycogen and cellulose are linked to the function of each of these
polysaccharides.
33. List the parts of a palisade cell that would be visible using an optical microscope.
 34. Describe the differences in structure between plant and animal cells that are visible using an
optical microscope.
35. Describe the structure of the plant cell wall as it would be seen using an electron microscope.
36. What are the functions of a plant cell wall?
37. Describe the structure of the chloroplast as it would be seen using an electron microscope.
38. What are the functions of a chloroplast?
39. Why are chloroplasts absent from root hair cells?
40. Why are chloroplasts absent from xylem vessels?
41. Plant cells known as parenchyma have large central vacuoles, thin cell walls and no
chloroplasts. Suggest what their function might be.

3.2.5
42. The replication of DNA is said to be semi-conservative. Explain what this term means.
43. Describe the stages involved in semi-conservative replication of DNA.
44. Explain carefully why semi-conservative replication produces two identical strands of DNA.
45. Briefly explain how experiments with viruses confirmed that DNA is the molecule of
inheritance.
46. List the stages of mitosis in the order in which they occur.
47. Describe what happens in each of the stages you have named.
48. Draw a diagram to show the cell cycle. In which part of the cycle does DNA replication take
place?
49. Some chemicals prevent the formation of the spindle during mitosis. Explain clearly why these
chemicals form the basis of a drug therapy for some cancers.

3.2.6
50. What takes place during cell differentiation?
51. In what ways does differentiation give a multicellular organism an advantage?
52. Explain the difference between a tissue and an organ. Give an example of each.
53. What is an organ system? Give an example.

3.2.7
54. Describe the relationship between the size of an organism and its surface area to volume ratio.
55. Describe how each of the following organisms carries out gas exchange. In each case also
refer to the process of diffusion: single-celled organism; insect; fish; dicotyledenous plant.
56. Explain how the conflicting needs of a large gas exchange surface and the requirement to
conserve water are resolved in insects and in xerophytic plants.
57. What are the main features of a mass flow transport system? Give an example of one such
system.
58. Name the four main blood vessels bringing blood to and from the heart. In each case give the
chamber of the heart the vessel is attached to, and the organ to or from which the blood is
flowing.
59. Mammals have a double circulatory system. Explain what this statement means.
60. Give the names of the blood vessels entering and leaving the kidneys and the liver.
61. In what way is the hepatic portal vein unusual?
62. Which organ is supplied by the coronary arteries?
63. Explain how the structure of arteries is related to their function.
64. How do the elastic walls of arteries help to regulate blood pressure?
65. How does the structure of veins adapt them to their function?
66. Describe the function and structure of a capillary.
67. How does tissue fluid form at a capillary bed, and how does if re-join the circulatory system?
 68. Describe carefully the routes by which water moves from the soil, through a plant and out into
the atmosphere.
69. Name the tissue through which water moves up the stem of a plant.
70. What is the difference between the symplast and the apoplast pathways?
71. Describe and explain the effect of each of the following on the rate of transpiration from a
plant: light, temperature, humidity, air movement, surface area.
72. Explain the roles of root pressure and cohesion tension in moving water through the xylem.

3.2.8
73. What is taxonomy? Why is it useful to biologists?
74. What are the main principles of a taxonomic system/
75. What are the taxonomic groups from the 5-kingdom taxonomic system?
76. Define a species.
77. What criteria may be used in the construction of phylogenic groupings?
78. Archaeopteryx is an extinct animal that has both teeth and feathers. Why is it difficult to
classify into a modern taxonomic group?

3.2.9
79. Why may DNA and proteins be of use in assigning organisms to taxonomic groups?
80. Explain why DNA hybridisation may show relationships between organisms.
81. What are the advantages of using proteins rather than DNA to classify organisms?
82. How may immunology be of use when comparing variation between proteins?
83. Courtship behaviour is an important part of the mating process in many animals. Why is this?

3.2.10
84. Explain one of the ways in which antibiotics act on bacteria when being used to treat bacterial
disease.
85. Name the genetic material found in bacteria.
86. What are mutations?
87. How may antibiotic resistance arise in bacteria?
88. What is vertical gene transmission? How may it spread antibiotic resistance in bacteria?
89. What is horizontal gene transmission? How may it spread antibiotic resistance in bacteria?
90. Discuss the difficulties of treating tuberculosis in terms of antibiotic resistance.
91. What ethical issues may arise when developing a new antibiotic/drug therapy?

3.2.11
92. What is the difference between species richness and species diversity?
93. Explain the effects that agriculture and deforestation have on species diversity.
94. An index of diversity may be calculated using the formula:
d = N(N-1)
∑n(n-1)
What do N and n stand for? What use is the value of d once it has been calculated?
95. How might this information be used when making decisions relating to land use and
development?