Biochemistry and cell organisation

• Inorganic ions


  • Occur in solution in the cytoplasm and bodily fluid of organisms
  • Some in high concentrations
  • Others in very low concentrations
• Ions required for plant growth and development

  • Nitrate ions required to make DNA and amino acids
  • Calcium ions
  • Chlorophyll
• Water


  A major component of cells<|>A polar molecule due to uneven distribution of charge<|>Used as a metabolite in metabolic reactions such as condensation and hydrolysis<|>A solvent in which many metabolic reactions occur<|>Has a high heat specific capacity, minimising temperature fluctuations in living things<|>Has a relatively large latent heat of vaporisation, providing a cooling effect with little water loss<|>Strong cohesion between molecules enables effective transport of water in tube-like transport cells
• Types of carbohydrates


  • Monosaccharides
  • Disaccharides
  • Polysaccharides
• Monosaccharides


  Small organic molecules used as the building blocks of complex carbohydrates<|>Have a varying number of carbon atoms, e.g. glyceraldehyde (triose), ribose (pentose), glucose (hexose)<|>Glucose is the main substrate for respiration and has two isomers, alpha and beta
• Disaccharides


  Formed by the condensation of two monosaccharides, e.g. maltose (glucose-glucose), sucrose (glucose-fructose), lactose (glucose-galactose)
• Chitin


  A polysaccharide made of chains of beta glucose monomers with amino acid side chains - one OH group of each beta glucose molecule is replaced with an amino acid
• Chitin


  • Lightweight but strong, used to form the exoskeletons of insects
• Lipids


  Biological molecules which are only soluble in organic solvents such as alcohols
• Types of lipids


  • Saturated
  • Unsaturated
• Saturated lipids


  • Found in animal fats, don't contain any carbon-carbon double bonds, too much can increase cholesterol levels and risk of coronary heart disease
• Unsaturated lipids


  • Found in plants, contain carbon-carbon double bonds, melt at lower temperatures than saturated fats, provide essential fatty acids
• Number of unsaturated bonds

  Weaker the intermolecular bonds, lower the melting point
• Triglycerides


  Lipids made of one molecule of glycerol and three fatty acids joined by ester bonds formed in condensation reactions
• Triglycerides


  • Vary in chain length, presence and number of double bonds, can contain a mix of different fatty acids
• Phospholipids


  One of the fatty acids of a triglyceride is substituted by a phosphate-containing group, phosphate heads are hydrophilic and tails are hydrophobic so they form micelles in water
• Triglycerides are used as energy reserves in plant and animal cells
• Amino acids


  Monomers from which proteins are made
• Amino acids


  • Contain an amino group (NH2), carboxylic acid group and a variable R group which is a carbon-containing chain
  • There are 20 different amino acids with different R groups
• Formation of peptide bonds

  1. Amino acids are joined by peptide bonds formed in condensation reactions

  2. A dipeptide contains two amino acids

  3. Polypeptides contain three or more amino acids
• Protein structure


  • Primary structure is the order and number of amino acids
  • Secondary structure is the shape the chain of amino acids makes (alpha helix or beta pleated sheet), determined by bonding (hydrogen, ionic, disulphide)
  • Tertiary structure is the 3D shape of the protein (globular or fibrous)
• Globular proteins


  • Enzymes
• Fibrous proteins


  • Keratin
• Collagen


  • Fibrous protein of great strength due to presence of hydrogen and covalent bonds
  • Collagen molecules wrap around each other and form fibrils which form strong collagen fibres
  • Collagen forms the structure of bones, cartilage and connective tissue, and is a main component of tendons
• Haemoglobin


  • Water soluble globular protein
  • Consists of two beta polypeptide chains and a haem group
  • Carries oxygen in the blood as oxygen can bind to the haem (Fe2+) group and oxygen is then released when required
• Alpha glucose


  A structural isomer of glucose that exists in a ring form where the hydroxyl group on carbon-1 lies below the plane of the ring
• Amino acids


  The monomers containing an amino group (NH), a carboxyl group (COOH) and a variable R group that make up proteins
• Benedict's test


  A biochemical test used to test for reducing sugars that produces a different colour based on the amount of reducing sugar present
• Beta glucose


  A structural isomer of glucose that exists in a ring form where the hydroxyl group on carbon-1 lies above the plane of the ring
• Biuret test


  A biochemical test that produces a purple colour when it is added to a solution containing protein
• Calcium ion (Ca)


  An ion required for the formation of calcium pectate which has a structural role in plant cell walls and membranes
• Cellulose


  A linear polysaccharide that is the main component of the cell wall in plants and is made up of many beta glucose molecules joined by B-14 glycosidic bonds
• Chitin


  A linear polysaccharide that is made up of chains of beta glucose molecules with amino acid side chains and is found in the exoskeletons of insects and crustaceans as well as fungal cell walls
• Cohesion


  A property of water molecules that creates an attraction between them and causes them to stick together
• Condensation reaction


  A type of reaction that joins two molecules together with the formation of a chemical bond involving the elimination of a molecule of water
• Disaccharides


  Molecules formed by the condensation of two monosaccharides eg lactose, sucrose, maltose
• Emulsion test


  A biochemical test that produces a cloudy emulsion when performed on lipids
• Ester bond


  A bond between a fatty acid chain and glycerol formed in a condensation reaction
• Fibrous protein


  A class of long chain proteins that are generally insoluble in water and typically have structural roles
• Globular protein


  A class of spherical shaped proteins that are generally water soluble and