Option B - Biochemistry
B.1 Introduction to biochemistry
Essential idea: Metabolic reactions involve a complex interplay between many different components in highly controlled environments.
Understandings The diverse functions of biological molecules depend on their structures and shapes. Applications and skills Explanation of the difference between condensation and hydrolysis reactions. Guidance: Intermediates of aerobic respiration and photosynthesis are not required. |
B.2 Proteins and enzymes
Essential idea: Proteins are the most diverse of the biopolymers responsible for metabolism and structural integrity of living organisms
Understandings Proteins are polymers of 2-amino acids, joined by amide links (also known as peptide bonds). Applications and skills Deduction of the structural formulas of reactants and products in condensation reactions of amino acids, and hydrolysis reactions of peptides. Guidance: The names and structural formulas of the amino acids are given in the data booklet in section 33. |
B.3 Lipids
Essential idea: Lipids are a broad group of biomolecules that are largely non-polar and therefore insoluble in water.
Understandings Fats are more reduced than carbohydrates and so yield more energy when oxidized. Applications and skills Deduction of the structural formulas of reactants and products in condensation and hydrolysis reactions between glycerol and fatty acids and/or phosphate. Guidance: The structures of some fatty acids are given in the data booklet in section 34. |
B.4 Carbohydrates
Essential idea: Carbohydrates are oxygen-rich biomolecules, which play a central role in metabolic reactions of energy transfer..
Understandings Carbohydrates have the general formula Cx(H2O)y. Applications and skills Deduction of the structural formulas of disaccharides and polysaccharides from given monosaccharides. Guidance: The straight chain and a-ring forms of glucose and fructose are given in the data booklet in section 34. |
B.5 Vitamins
Essential idea: Vitamins are organic micronutrients with diverse functions that must be obtained from the diet.
Understandings Vitamins are organic micronutrients which (mostly) cannot be synthesized by the body but must be obtained from suitable food sources.
Applications and skills Comparison of the structures of vitamins A, C and D. Guidance: The structures of vitamins A, C and D are provided in the data booklet section 35. |
B.6 Biochemistry and the environment
Essential idea: Our increasing knowledge of biochemistry has led to several environmental problems, while also helping to solve others
Understandings Xenobiotics refer to chemicals that are found in an organism that are not normally present there. Applications and skills Discussion of the increasing problem of xenobiotics such as antibiotics in sewage treatment plants. Guidance: Specific names of green chemicals such as solvents are not expected. |
B.7 Proteins and enzymes
Essential idea: Analyses of protein activity and concentration are key areas of biochemical research.
Understandings Inhibitors play an important role in regulating the activities of enzymes. Applications and skills Determination of the maximum rate of reaction (Vmax) and the value of the Michaelis constant (Km) for an enzyme by graphical means, and explanation of its significance. Guidance: The effects of competitive and non-competitive inhibitors on Km and Vmax values should be covered. |
B.8 Nucleic acids
Essential idea: DNA is the genetic material that expresses itself by controlling the synthesis of proteins by the cell.
Understandings Nucleotides are the condensation products of a pentose sugar, phosphoric acid and a nitrogenous baseadenine (A), guanine (G), cytosine (C), thymine (T) or uracil (U). Applications and skills Explanation of the stability of DNA in terms of the interactions between its hydrophilic and hydrophobic components. Guidance: Structures of the nitrogenous bases and ribose and deoxyribose sugars are given in the data booklet in section 34. |
B.9 Biological pigments
Essential idea: Use of dataquantitative measurements of absorbance are a reliable means of communicating data based on colour, which was previously subjective and difficult to replicate. (3.1)
Understandings Biological pigments are coloured compounds produced by metabolism. Applications and skills Explanation of the sigmoidal shape of hemoglobins oxygen dissociation curve in terms of the cooperative binding of hemoglobin to oxygen. Guidance: The structures of chlorophyll, heme B and specific examples of anthocyanins and carotenoids are given in the data booklet in section 35; details of other pigment names and structures are not required. |
B.10 Stereochemistry in biomolecules
Essential idea: Most biochemical processes are stereospecific and involve only molecules with certain configuration of chiral carbon atoms.
Understandings With one exception, amino acids are chiral, and only the L-configuration is found in proteins. Applications and skills Description of the hydrogenation and partial hydrogenation of unsaturated fats, including the production of trans-fats, and a discussion of the advantages and disadvantages of these processes. Guidance: Names of the enzymes involved in the visual cycle are not required. |