bio molecules

• Monomer 


  a small molecular unit which can be used to make larger molecules like monosaccharides, amino acids and nucleotides
• Polymers


  molecules made from many monomers joined together
• Condensation reaction

  monomers joined by a chemical bond releasing a water molecule in the process
• Monosaccharides

  • is a single monomer
  • examples include: glucose, fructose and galactose
  • glucose has two isomers: alpha and beta
• Disaccharides

  • is a pair of monomers
  • formation of a glycosidic bond
  • examples: maltose [two glucose molecules], sucrose [glucose and fructose] and lactose [glucose and galactose]
• Polysaccharides

  • are many monosaccharides
  • glycogen and starch made of a-glucoses
  • cellulose made of b-glucose molecules
• Glycogen

  • main energy source in animals
  • made of a-glucose by 1,4 and 1,6 glycosidic bonds
  • large number of side branches = energy can be released quickly
  • large but compact = maximising the amount of energy it can store
  • insoluble = cannot effect water potential of cells
• Starch

  • found in plants and is isotonic
  • amylose: a-glucose molecules by 1,4 glycosidic bonds meaning un-branched and is coiled and compact = storing lots of energy
  • amylopectin: a-glucose molecules by 1,4 and 1,6 glycosidic bonds meaning branched so release energy quickly
• Cellulose

  • component of cell wall in plants
  • made up of b-glucose molecules by 1,4 glycosidic bonds meaning unbranched
  • microfibrils = hydrogen bonds which form strong cross linkages
  • helps cells stay turgid and rigid to maximise the SA of plants for photosynthesis
• Benedict's test [reducing sugars]

  • add benedict's reagent to a food sample
  • heat in a water bath
  • positive result: turns brick red colour
• Non-reducing sugars

  • if negative result in reducing sugars test
  • add dilute hydrochloric acid to food sample and heat in water bath
  • then add sodium hydrogen carbonate to neutralise
  • add benedict's reagent and heat in water bath
  • positive result: colour change from blue to brick red
• Triglycerides

  • one molecule of glycerol and three fatty acid chains
  • formed by condensation reactions creating ester bonds
  • saturated = no carbon-carbon double bond
  • un-saturated = contains carbon-carbon double bond
• Phospholipids

  • made of glycerol molecule, two fatty acid chains and a phosphate group
  • phosphate "heads" are hydrophilic = attracts water
  • fatty acid "tails" are hydrophobic = repels water
  • helps to form phospholipid bilayer in cell membrane
• Emulsion test

  • test for the presence of lipids
  • add ethanol to food sample and shake vigorously
  • the add water and shake gently
  • positive result: cloudy white emulsion/precipitate
• Proteins

  • amino acids contain amino group [NH2], carboxyl group [COOH] and a R group which determines the type of amino acid
  • formed by condensation reactions creating peptide bonds
  • dipeptide = two amino acids
  • polypeptide = three or more amino acids
• Structure of proteins 


  Primary: initial sequence of amino acids

  Secondary: hydrogen bonds create either alpha helixes or beta pleated sheets

  Tertiary: further folding with hydrogen and ionic bonds and disulfide bridges

  Quaternary: multiple polypeptide chains bonded together to create a 3d structure
• Biuret test

  • test for the presence of protein
  • add sodium hydroxide to food sample
  • then add dilute copper sulphate solution and mix
  • positive result: colour change from blue to purple
• Enzymes

  • increase the rate of the reaction by lowering the activation energy
  • have an active site which is complementary to a substrate
  • create a enzyme substrate complex to break the substrate into products
• Lock and key model

  • the shape of the active site is exact to the shape of the substrate
  • so enzyme substate complexes form easily
• Induced fit model

  • the shape of the active site changes slightly when binding with a substrate so is more flexible
  • the induced fit model is better than the lock and key model
• Factors affecting enzyme rate of reaction

  • temp and pH: increases rate of reaction up until optimum then beyond that it becomes denatured so decreases
  • enzyme and substrate concentration: increases rate of reaction until maximum amount of enzyme substrate complexes are formed then platos
  • competitive inhibitors: bind to the active site as have same shape so block substrates and decrease rate of reaction
  • non-competitive inhibitors: bind away from the active site changing the tertiary structure of the enzyme which alters the active site shape and decrease rate of reaction
• DNA

  • deoxyribonucleic acid
  • stores genetic material of a cell
  • deoxyribose sugar
  • contains thymine
  • double stranded
  • long
  • discovered by Watson and Crick
  • self replicating
• RNA

  • ribonucleic acid
  • carriers out the instruction encoded in DNA to make proteins
  • ribose sugar
  • single stranded
  • contains uracil
  • short
  • synthesised by transcription
• Semi-conservative replication

  • DNA helicase breaks the hydrogen bonds between the bases causing the DNA molecule to uncoil
  • one DNA strand acts as a template for free nucleotides to bind to for complementary base pairing
  • adenine binds to thymine with two hydrogen bonds
  • guanine binds to cytosine with three hydrogen bonds
  • DNA polymerase forms the phosphodiester bonds between the new nucleotides
  • the new DNA molecule contains one strand from the original molecule and one new strand making it semi-conservative
• ATP

  • adenosine triphosphate
  • made up of ribose sugar, adenine base and three phosphate groups
  • ATP is hydrolysed by ATP hydrolase into ADP and Pi which releases energy
  • ATP and Pi is catalysed by ATP synthase into ATP
• Properties of ATP

  • Pi is used to phosphorylate other compounds making them more reactive
  • gives an immediate source of energy that is given in manageable quantities
  • ATP isn't stored
  • used in metabolic processes, movement, active transport, secretion and activation of molecules
• Water

  • polar molecule: due to uneven distribution of charge allowing hydrogen bonds to from between water molecules
  • metabolite: involved in condensation and hydrolysis reactions
  • solvent: allows substances to readily diffuse
  • high specific heat capacity: minimises temperature fluctuations acting as a buffer
  • relatively large latent heat of vaporisation: provides a cooling effect with little water loss
  • strong cohesion: supports columns of water as the surface tension at the water-air boundary is high
• Inorganic ions

  • hydrogen ions: determine the pH as the higher the concentration the lower the pH
  • iron ions: found in haemoglobin allowing oxygen to bind to it
  • sodium ions: involved in co-transport of glucose and amino acids across cell membrane
  • phosphate ions: component of nucleotides like DNA, RNA and ATP