Biological molecules

    AQA
    A-Level

    This topic explores the fundamental biochemistry of life, focusing on the chemical structure and biological functions of carbohydrates, lipids, proteins, nucleic acids, and water. It examines the relationship between molecular structure and function, detailing how monomers form polymers via condensation reactions and degrade through hydrolysis. The content covers the specific properties of biological macromolecules, the mechanism of enzyme action including kinetics and inhibition, and the vital roles of inorganic ions and water in metabolic processes.

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    Objectives
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    Learning Objectives

    What you need to know and understand

    • Monomers are the smaller units from which larger molecules are made.
    • Polymers are molecules made from a large number of monomers joined together.
    • A condensation reaction joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water.
    • A hydrolysis reaction breaks a chemical bond between two molecules and involves the use of a water molecule.
    • Monosaccharides are the monomers from which larger carbohydrates are made. Glucose, galactose and fructose are common monosaccharides.
    • A condensation reaction between two monosaccharides forms a glycosidic bond.
    • Disaccharides are formed by the condensation of two monosaccharides: maltose, sucrose, lactose.
    • Glucose has two isomers, alpha-glucose and beta-glucose.
    • Polysaccharides are formed by the condensation of many glucose units: glycogen, starch, cellulose.
    • Triglycerides and phospholipids are two groups of lipid.
    • Triglycerides are formed by the condensation of one molecule of glycerol and three molecules of fatty acid.
    • In phospholipids, one of the fatty acids of a triglyceride is substituted by a phosphate-containing group.
    • Amino acids are the monomers from which proteins are made.
    • A condensation reaction between two amino acids forms a peptide bond.
    • The relationship between primary, secondary, tertiary and quaternary structure, and protein function.
    • The induced-fit model of enzyme action.
    • DNA holds genetic information and RNA transfers genetic information from DNA to the ribosomes.
    • DNA and RNA are polymers of nucleotides.
    • The semi-conservative replication of DNA ensures genetic continuity between generations of cells.

    Key Terminology

    Essential terms to know

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