Molecules

• Water as a solvent

  • Transport
  • Removal of wastes
  • Secretions
• Potassium

  • Cation+Anion balance across cell membrane
  • Maintaining osmotic balance across cell membrane
  • Enzyme cofactor
• Calcium

  • Calcium pectate binds adjacemt cell walls in plants
  • Required in blood clotting
• Magnesium

  • Prosthetic group in chlorophyll
  • Mg2+ ions activate enzymes
• Iron

  • prosthetic group of haemoglobin
• Hydrogencarbonate

  • Transport of CO2 in the blood
  • Behaves as a buffer in the blood
• Nitrate

  • Protein constituent
  • Nucleic acid constituent
  • ATP ADP
• Phosphate

  • constituent of membranes as phospholipids
  • ATP ADP
  • in nucleotides
• Carbohydrates

  • Carbon Hydrogen Oxygen
  • CH2O
• Monomer


  single unit building block
• Dimmer


  When two monomers are joined
• Polymer


  A molecule made of many monomers
• Monosaccharides

  • Single unit sugars
  • a-glucose and b-glucose
• Isomers


  molecules with the same molecular formula but different structural arrangement
• Disaccharides

  • double unit sugars
  • formed when monosaccharides join during a condensation reaction
  • a-glucose+a-glucose: maltose
  • a-glucose+fructose: sucrose
  • a-glucose+galactose: lactose
• Condensation


  releases water to form a covalent bond
• The bond formed between two monosaccharides is a glycosidic bond.
• Maltose

  • found in germinating seeds
  • starch is changed into maltose for use by respiring cells of the embryo
• Sucrose

  • Household sugar
  • Main form in which carbohydrate is transported in plants
• Polysaccharides

  • Long chains of sugar monomers linked by glycosidic bonds
  • Starch, Glycogen, Cellulose
  • Insoluble in water, non-sweet and cannot be crystallised
  • Energy store or structural components
• Starch

  • Amylose and amylopectin
  • alpha glucose
  • found in plants
  • energy store
  • chloroplasts, cytoplasm, storage tissue
  • insoluble, compact, unreactive
• Amylose

  • unbranched chains of a-glucose
  • 1,4-linked
  • position of glycosidic bonds and attraction of OH groups makes the long monomer chain wind into a helix
• Amylopectin

  • branched chains made of a-glucose
  • 1,4 and 1,6-linked
  • chains are multihelical
  • many terminal end glucose molecules- more readily hydrolysed
• Glycogen

  • long, highly branched chains of a-glucose molecules
  • held together by 1,4 and 1,6-linked glycosidic bonds
  • insoluble, compact, unreactive
• Cellulose

  • b-glucose
  • plant cell walls
  • provides strength, support and rigidity
  • straight, unbranched chains of b-glucose
  • 1,4-linked joined by glycosidic bonds
  • alternate molecules are rotated through 180 to allow glycosidic bonding
• Cellulose

  • parallel chains held together by glycosidic bonds
  • insoluble, strong and hard to digest
  • provides strength and rigidity
  • layers of cellulose b-glucose chains are held together by hydrogen bonds and arranged at varying angles, adding to tensile strength
• Lipids

  • Carbon, hydrogen, oxygen
  • 1 glycerol and 3 fatty acids
  • fatty acids joined to glycerol by ester bond- condensation reaction
  • saturated: no carbon double bond, solid, animals, fat
  • unsaturated: at least one carbon double bond, liquid, plants, oil
• Lipids

  • most are triglycerides
  • non-polar
  • insoluble
  • less dense than water
• Function of Lipìds

  • Phospholipids are major components of cell membranes, fatty acid tails are hydrophobic, phosphate heads are hydrophilic
  • Cholesterol is a steroid in cell membranes
  • Energy store
  • protection and insulation
  • waterproofing
  • water storage
• Proteins

  • Carbon, Hydrogen, Oxygen and Nitrogen
  • amino acids joined by peptide bonds
  • the chemical nature of the r-group determines the type of amino acid
• Peptide bond


  A peptide bond is formed when a water molecule is lost in a condensation reaction, when ther amino group of one amino acid reacts with the carboxyl group of another, a dipeptide is formed.
• Polypeptide

  A molecule formed whenever a number of amino acids are joined together
• Primary protein structure

  • sequence of amino acids in a polypeptide chain
  • linked by peptide bonds between adjacent amino and carboxyl groups
• Secondary structure

  • spiralling of polypeptide chain to form an a-helixç
  • an alternative structure is a b-pleated sheet
  • held together by hydrogen bonds
• Tertiary structure

  • folding of the polypeptide chain
  • provides a compact globular shape
  • held in shape by bonds between neighbouring r-groups
  • these bonds include hydrogen bonds, ionic bonds, hydrophobic interactions and disulphide bridges
• Quaternary structure

  • occurs when the functional protein consists of two or more interacting polypeptide chains
  • disulphide bridges form crosslinks holding the structure in shape
• Conjugated protein


  A protein which contains a non-protein group known as a prosthetic group
• Globular

  • tertiary, quaternary, may be conjugated
  • soluble
  • haemoglobin, enzymes, hormones
• Fibrous

  • secondary
  • insoluble
  • collagen, keratin
• Collagen

  • fibrous protein
  • helical shape
  • provides tensile strength in connnective tissues
  • many crosslinks and hydrogen bonds allows the formation of folded polypeptide chains which winde around each other giving high tensile strength.