The aim of this option is to give students an understanding of the chemistry of important molecules found in the human body and the need for a balanced and healthy diet. Although the role these molecules play in the body should be appreciated, the emphasis is placed on their chemistry, and students who have not followed a course in biology will not be at a disadvantage. Students will not be required to memorise complex structures but will be expected to recognize functional groups and types of bonding within molecules. Structures of some important biological molecules are given in the data booklet.
C.1 Diet (2h)
C.1.1 Describe what the human body requires for a
Students should recognise the importance of a balanced diet, including minimum requirements and the need for
C.1.2 Calculate the calorific value of a food from enthalpy of combustion data.
C.1.3 Discuss the benefits and concerns of using
genetically modified (GM) foods.
Crops and animals can be modified to provide more food, be more resistant to disease and be more tolerant to
heavy metals. Concerns include the release of genetically modified organisms into the environment where they
could spread and compete with the naturally occurring varieties.
C.2 Proteins (3h)
C.2.1 State the basic structure of 2-amino acids.
There are approximately 20 common 2-amino acids (a -amino acids) found in organism. 2 amino acids have the
C.2.2 Describe the condensation reaction of amino acids to form polypeptides.
C.2.3 Explain how proteins can be analysed by
chromatography and electrophoresis.
To use either of these techniques the peptide bonds in the proteins must first by hydrolysed to release individual
amino acids. Include the use of Rf values in paper chromatography. Give isoelectric points, students should be
able to determine a suitable pH to achieve good separation in electrophoresis.
C.2.4 Describe and explain the primary, secondary, tertiary and quaternary structure of proteins.
C.2.5 List the major functions of proteins in the
These are structure, biological catalysts (enzymes) and energy sources.
C.3 Carbohydrates (2.5h)
C.3.1 Describe the structural features of
Monsaccharides contain a carbonyl group (C=O) and at least two -OH groups, and have the empirical formula
C.3.2 Describe the straight-chain formula of glucose and the structural difference between a -glucose and b -glucose.
C.3.3 Describe the condensation of monosaccharides to form disaccharides and polysaccharides.
Limit examples to :
C.4 Fats (2.5h)
C.4.1 Describe the composition of fats and oils.
C.4.2 Describe the difference in structure between
saturated and unsaturated fats, and explain the difference in their melting
C.4.3 Calculate the number of C=C double bonds in an
unsaturated fat using addition reactions.
The number of C=C bonds can be determined from the number of moles of I2 which add to one mole of fat.
C.4.4 Describe the hydrolysis of fats to form soaps and the action of soaps.
C.4.5 List the major functions of fats in the body.
These are energy sources, insulation and cell membranes.
C.5 Vitamins (2.5 H)
C.5.1 Define the term vitamin.
C.5.2 Deduce whether a vitamin is water or fat soluble from its structure.
C.5.3 Describe the structures
and major functions of retinol (vitamin A), calciferol (vitamin D) and ascorbic
C.5.4 Describe the effects of food processing on the vitamin content of food.
Most vitamins are unstable at higher temperatures so will be affected by prolonged cooking.
C.6 Hormones (2.5h)
C.6.1 Outline the production and roles of hormones in
Hormones are chemical messengers produced in glands controlled by the pituitary gland, which in turn is
controlled by the hypothalamus. Limit examples of production and roles to adrenalin, thyroxine, insulin and sex
C.6.2 Compare the structures of cholesterol and the
Stress the common steroid backbone but the difference in functional groups (see the data booklet).
C.6.3 Describe the mode of action of oral contraceptives.
C.6.4 Outline the use and abuse of steroids.
C.7 Enzymes (3h)
C.7.1 Outline the basic characteristics of enzymes.
C.7.3 Describe the significance of Vmax and Kn.
C.7.4 Describe the concept of the active site in enzyme structure.
C.7.5 Explain competitive inhibition and non-competitive inhibition.
C.7.6 State and explain the effects of heavy metal ions, extremes of temperature and pH changes on enzyme activity.
C.7.7 Describe the uses of enzymes in biotechnology.
Possible examples include proteases in biological detergents, glucose isomerase converting glucose to fructose
and streptokinase in breaking down blood clots.
C.8 Nucleic Acids (2h)
C.8.1 Describe the structure of nucleotides and their
condensation polymers (nucleic acids).
A nucleotide contains a phosphate group, a pentose sugar group and an organic base. Students should be able to
recognise, but need not recall, the structures of the five nucleotide bases : adenine, cytosine, guanine, thymine and
C.8.2 Describe the double helical structure of DNA.
Students should be able to describe the hydrogen bonding between specific pairs of nucleotide bases.
C.8.3 Outline the role of DNA as the repository of genetic information, including the triplet code.
C.8.4 Describe the principles and uses of DNA profiling.
Include forensic uses and paternity cases.
C.9 Metal Ions in Biological Systems (2h)
C.9.1 Explain that different metal ions fulfill different
roles in the body due to their different chemical properties.
Emphasise differences in charge density, redox properties and complex ion formation.
C.9.2 Describe the importance of the difference in
Na+ and K+ concentrations across the cell membrane.
Explain active transport using the Na+/K+ pump as an example.
C.9.3 Outline the importance of copper ions in electron
transport and iron ions in oxygen carriers.
Use cytochromes and haemoglobin as examples.