AS Spec

• Sections 1–4 are designed to be covered in the first year of the A-level and are also the AS subject content. So you can teach AS and A-level together.
• The overview is intended to encourage an overarching approach to both the teaching and learning of topic areas. As such, it will not be directly assessed.
• The codes in the right-hand column refer to the skills in the relevant appendices. MS refers to the Mathematical Skills, AT refers to the Apparatus and Techniques and PS refers to the Practical Skills.
• Monomers


  Smaller units from which larger molecules are made
• Polymers


  Molecules made from a large number of monomers joined together
• Monomers


  • Monosaccharides, amino acids and nucleotides
• Condensation reaction


  Joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water
• Hydrolysis reaction


  Breaks a chemical bond between two molecules and involves the use of a water molecule
• Monosaccharides


  The monomers from which larger carbohydrates are made. Glucose, galactose and fructose are common monosaccharides.
• Condensation reaction between two monosaccharides

  Forms a glycosidic bond
• Disaccharides


  • Maltose (glucose + glucose), sucrose (glucose + fructose), lactose (glucose + galactose)

  
• Glucose has two isomers, α-glucose and β-glucose

  
• Polysaccharides


  • Formed by the condensation of many glucose units. Glycogen and starch are formed by the condensation of α-glucose. Cellulose is formed by the condensation of β-glucose.

  
• The basic structure and functions of glycogen, starch and cellulose. The relationship of structure to function of these substances in animal cells and plant cells.
• Biochemical tests using Benedict's solution for reducing sugars and non-reducing sugars and iodine/potassium iodide for starch.
• Triglycerides


  Formed by the condensation of one molecule of glycerol and three molecules of fatty acid
• Condensation reaction between glycerol and a fatty acid

  Forms an ester bond
• Fatty acids


  The R-group may be saturated or unsaturated
• Phospholipids


  One of the fatty acids of a triglyceride is substituted by a phosphate-containing group
• The different properties of triglycerides and phospholipids related to their different structures.
• The emulsion test for lipids.
• Amino acids


  The monomers from which proteins are made. The general structure is NH2-CH-COOH, where R represents a side chain.

  
• Condensation reaction between two amino acids

  Forms a peptide bond
• Dipeptides


  Formed by the condensation of two amino acids
• Polypeptides


  Formed by the condensation of many amino acids
• A functional protein may contain one or more polypeptides.
• Protein structure


  • The role of hydrogen bonds, ionic bonds and disulfide bridges in the structure of proteins. The relationship between primary, secondary, tertiary and quaternary structure, and protein function.

  
• The biuret test for proteins.
• Enzymes


  Each enzyme lowers the activation energy of the reaction it catalyses.
• Properties of enzymes


  • The specificity of enzymes. The effects of enzyme concentration, substrate concentration, concentration of competitive and non-competitive inhibitors, pH and temperature on the rate of enzyme-controlled reactions.
• Required practical 1: Investigation into the effect of a named variable on the rate of an enzyme-controlled reaction.
• DNA and RNA


  Important information-carrying molecules. DNA holds genetic information and RNA transfers genetic information from DNA to the ribosomes.
• Nucleotides


  The components are a pentose, a nitrogen-containing organic base and a phosphate group. DNA nucleotides have deoxyribose and one of the bases adenine, cytosine, guanine or thymine. RNA nucleotides have ribose and one of the bases adenine, cytosine, guanine or uracil.

  
• Condensation reaction between two nucleotides

  Forms a phosphodiester bond
• DNA molecule


  A double helix with two polynucleotide chains held together by hydrogen bonds between specific complementary base pairs.
• RNA molecule


  A relatively short polynucleotide chain.

  
• The semi-conservative replication of DNA ensures genetic continuity between generations of cells.
• DNA replication


  Unwinding of the double helix, breakage of hydrogen bonds between complementary bases, role of DNA helicase and DNA polymerase.
• A single molecule of adenosine triphosphate (ATP) is a nucleotide derivative and is formed from a molecule of ribose, a molecule of adenine and three phosphate groups.

  
• Hydrolysis of ATP to ADP and Pi


  Catalysed by the enzyme ATP hydrolase