Biological Molecules

Monomers and polymers

c   Monomers are the smaller units from which larger molecules are made.

c   Polymers are molecules made from a large number of monomers joined together.

c   Monosaccharides, amino acids and nucleotides are examples of monomers.

Water

c   Water is a major component of cells. It has several properties that are important in biology. In particular, water: is a metabolite, a solvent, has a high heat capacity, has a large latent heat of vaporisation and has strong cohesion between molecules.

Lipids

c   Triglycerides and phospholipids are two groups of lipid.

c   A condensation reaction joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water.

c   A hydrolysis reaction breaks a chemical bond between two molecules and involves the use of a water molecule.

c   Triglycerides are formed by the condensation of one molecule of glycerol and three molecules of fatty acid (RCOOH) through the formation of an ester bond.

c   The R-group of a fatty acid may be saturated or unsaturated.

c   The structure of phospholipids, and how this structure relates to their properties.

c   The emulsion test for lipids.

Carbohydrates

c   Glucose has two isomers, α -glucose and β –glucose.

c   Monosaccharides, including glucose, galactose and fructose, are monomers from which larger carbohydrates are made.

c   Condensation reactions produce disaccharides through the formation of glycosidic bonds. These include maltose, sucrose and lactose.

c   Polysaccharides are formed by the condensation of many glucose units: Glycogen and starch are polysaccharides formed by condensation of α-glucose. Cellulose is formed by the condensation of β-glucose.

c   Identify the biochemical tests for reducing sugars, non-reducing sugars and starch.

c   Calibration curves can be used to provide quantitative data on the concentration of unknown starch solutions.

Proteins

c   The general structure of amino acids and how the only difference between amino acids in their side group

c   The biuret test for proteins.

c   Amino acids can be separated by Thin Layer Chromatography

c   The formation of dipeptides and polypeptides through condensation of amino acids.

c   The relationship between primary, secondary, tertiary and quaternary structure, and protein function.

c   The role of hydrogen bonds, ionic bonds and disulphide bridges in the structure of proteins.

c   The roles played by proteins.

Enzymes

c   Enzyme catalysis and activation energy.

c   Calculate initial rate.

c   The induced-fit model of enzyme action.

c   Enzyme specificity linked to active site structure.

c   The properties of an enzyme relate to the tertiary structure of its active site in the formation of an enzyme-substrate complex. 

c   The effects of the following factors on the rate of enzyme controlled reactions – enzyme concentration, substrate concentration, concentration of competitive and of non-competitive inhibitors, pH and temperature.

c   Required practical 1: Investigation into the effect of a named variable on the rate of anenzyme-controlled reaction

DNA and RNA

c   Deoxyribonucleic acid is important in all living cells, as it holds genetic information.

c   DNA is a polymer of nucleotides formed by condensation, with phosphodiester bonds between nucleotides.

c   Each nucleotide is formed from a deoxyribose, a nitrogen-containing organic base and a phosphate group.

c   DNA is a double helix, held together by hydrogen bonds between complementary bases.

c   Ribonucleic acid is important in all living cells, as it transfers genetic information from DNA to ribosomes.

c   RNA is a polymer of nucleotides formed by condensation, with phosphodiester bonds between nucleotides.

c   Each nucleotide is formed from a ribose, a nitrogen-containing organic base and a phosphate group.

c   An RNA molecule is a relatively short polynucleotide chain.

c   Ribosomes are formed from RNA and proteins.

DNA replication

c   The semi-conservative replication of DNA ensures geneticcontinuity between generations of cells.

c   The process of semi-conservative replication of DNA, including the role of DNA polymerase.

ATP

c   A single molecule of ATP is a nucleotide derivative, formed from a molecule of ribose, a molecule of adenine and three phosphate groups.

c   Hydrolysis of ATP to ADP and Pi is catalysed by the enzyme ATP hydrolase, and can be used to phosphorylate compounds or provide energy to energy-requiring cellular reactions.

c   ATP is resynthesised from ADP and Pi by the enzyme ATP synthase, during photosynthesis or respiration.

Inorganic ions

c   Inorganic ions occur in solution in the cytoplasm and body fluids of organisms, some in high concentrations and others in very low concentrations.

c   Each type of ion has a specific role, depending on its properties.

c   Students should be able to recognise the role of ions in the following topics: hydrogen ions and pH; iron ions as a component of

c   haemoglobin; sodium ions in the co-transport of glucose and amino acids; and phosphate ions as components of DNA and of ATP.