Biochemistry

Chemical elements and Water
State that the most frequently occurring chemical elements in living things are carbon, hydrogen and oxygen.
State that a variety of other elements are needed by living organisms including nitrogen, calcium, phosphorus, iron and sodium.
State one role for each of the elements mentioned in 2.1.2.
Refer to the roles in both plants and animals.
Outline the difference between an atom and an ion.
Outline the properties of water that are significant to living organisms including transparency, cohesion, solvent properties, and thermal properties. Refer to the polarity of water molecules and hydrogen bonding where relevant.
Quantitative details of bond angles, bond strengths, or electronegativity are not required. One example to illustrate the importance of each property is sufficient. Thermal properties - refer to the large amounts of energy required to heat up water and change its state (and the reverse). Solvent properties - water is capable of dissolving many organic and inorganic substances.
Explain the significance to organisms of water as a coolant, transport medium and habitat, in terms of its properties.
Both plants and animals should be mentioned. No physical, chemical or quantitative details are required.
Carbohydrates, lipids and proteins
Define organic.
Compounds containing carbon that are found in living organisms (except hydrogencarbonates, carbonates and oxides of carbon) are regarded as organic.
Draw the basic structure of a generalized amino acid.
No details of R group are required.
Draw the ring structure of glucose and ribose.
Draw the structure of glycerol and a generalized fatty acid.
The IUPAC name of glycerol will not be used. The term 'fatty acid' can refer to aliphatic and aromatic fatty acids.
Outline the role of condensation and hydrolysis in the relationships between monosaccharides, disaccharides and polysaccharides; fatty acids, glycerol and glycerides; amino acids, dipeptides and polypeptides.
Draw the structure of a generalized dipeptide showing the peptide linkage.
Neither the fact the linkage is planar nor that it permits rotation about the C-N bond is required.
List two examples each of monosaccharides, disaccharides and polysaccharides.
Only the names and the names of the monomer units are required, not structural formulae.
State one function for a monosaccharide and one for a polysaccharide.
State three functions of lipids.
Discuss the use of carbohydrates and lipids in energy storage.
Explain the four levels of structure of proteins, indicating each level's significance.
Quanternary structure may involve the binding of a prosthetic group to form a conjugated protein.
Outline the difference between fibrous and globular proteins, with reference to two examples of each protein type.
Explain the significance of polar and non-polar amino acids.
Limited this to controlling the position of proteins in membranes, creating hydrophilic channels through membranes and the specificity of active sites in enzymes. Cross reference with 1.4.
State six functions of proteins, giving a named example of each.
Membrane proteins should not be included.
Enzymes
Define enzyme and active site.
State that metabolic pathways consist of chains and cycles of enzyme catalyzed reactions.
Explain that enzymes lower the activation energy of the chemical reactions that they catalyze.
Graphical representation of both exergonic and endergonic reactions should be covered, but no specific energy values need be recalled.
Explain enzyme-substrate specificity.
The lock-and-key model can be used as a basis for the explanation.
Describe the "induced fit" model.
This is an extension of the 'lock-and-key' model. Its importance in accounting for the broad specificity of some enzymes (the ability to bind several substrates) should be mentioned.
Define denaturation.
Denaturation -- a structural change in a protein that results in a loss (usually permanent) of its biological properties. Refer only to heat and pH as agents.
Explain the effects of temperature, pH and substrate concentration on enzyme activity.
Cross reference with 5.6.1. For temperature and pH, refer to denaturation of the active site.
Explain the difference between competitive and non-competitive inhibition, with reference to one example of each.
Competitive: an inhibiting molecule structually similar to the substrate molecule binds to the active site preventing the substrate binding. Examples: inhibition of butanedioic acid (succinate) dehydrogenase by propanedioic acid (malonate) in the Krebs cycle and inhibition of folic acid synthesis in bacteria by the sulfonamide Prontosil™ (an antibiotic).
Non-competitive: limited to an inhibitor molecule binding to an enzyme (not to its active site) that causes a conformational change in its active site, resulting in a decrease in activity. Examples include Hg2+, Ag+, Cu2+, and CN- inhibition of many enzymes (eg cytochrome oxidase) by binding to -SH groups, thereby breaking -S-S- linkages; nerve gases like Sarin and DFP (diisopropyl fluorophosphate) inhibiting ethanoyl (acetyl) cholinesterase.
Reversible inhibition, as compared to irreversible inhibition is not required.
Explain the role of allostery in the control of metabolic pathways by end-product inhibition..
Allostery as a form of non-competitive inhibition. Mention that the shape of allosteric enzymes can be altered by the binding of end products to an allosteric site, therby decreasing its activity. Metabolites can act as allosteric inhibitors of enzymes earlier in a metabolic pathway and regulate metabolism according to the requirements of organisms; a form of negative feedback. Examples include ATP inhibition of phosphofructokinase in glycolysis and inhibition of aspartate carbamoyltransferase (ATCase) which catalyzes the first step in pyrimidine synthesis.
Explain the use of pectinase in fruit juice production, and one other commercial application of enzymes in biotechnology.
Applications could include the use of enzymes in biological washing powder, tenderizing meat or production of glucose syrup. Detailed chemistry is not expected, but reasons for the use of biotechnology as well as the advantages conferred by it are required.