💦Biology Unit 1 Biological Molecules

• Organic compounds


  Contain carbon-carbon bonds
• Inorganic compounds


  Do not contain carbon-carbon bonds
• Three important types of chemical bonds in biochemistry

  • Covalent bonds
  • Ionic bonds
  • Hydrogen bonds
• Covalent bonds


  • Strong, main bonds holding atoms together in organic molecules, always made/broken by enzymes
• Ionic bonds


  • Fairly strong, formed between positive and negative ions, not common in biology
• Hydrogen bonds


  • Much weaker, can break and form spontaneously at biological temperatures

  
• Water molecules


  • Charged dipole, with oxygen slightly negative and hydrogen slightly positive, forming hydrogen bonds
• Properties of water due to its dipole nature


  • Good solvent
  • High specific heat
  • High latent heat
  • Cohesive and adhesive
  • Most dense at 4°C
  • Incompressible
• Hydrophilic


  Charged or polar molecules that dissolve readily in water
• Hydrophobic


  Uncharged or non-polar molecules that do not dissolve well in water
• Monosaccharides


  Smallest units of carbohydrates, have formula (CH2O)n where n can be 3-7
• Types of monosaccharides


  • Hexose sugars (C6H12O6, e.g. glucose, galactose, fructose)
  • Pentose sugars (C5H10O5, e.g. ribose, deoxyribose, ribulose)
  • Triose sugars (C3H6O3)
• Disaccharides


  Formed when two monosaccharides are joined by a glycosidic bond, with loss of a water molecule
• Common disaccharides

  • Maltose (glucose - glucose)
  • Sucrose (glucose - fructose)
  • Lactose (glucose - galactose)
• Condensation reaction


  Two molecules combine into one larger molecule, with loss of water
• Hydrolysis reaction


  Large molecule is broken into smaller ones by reacting with water
• Disaccharides


  Formed when two monosaccharides are joined together by a glycosidic bond (C–O–C)
• Disaccharide formation


  Involves the formation of a molecule of water (H2O)
• Disaccharides


  • Maltose (glucose-glucose)
  • Sucrose (glucose-fructose)
  • Lactose (galactose-glucose)
• Maltose


  Glucose-glucose, formed on digestion of starch by amylase
• Sucrose


  Glucose-fructose, common in plants as it is less reactive than glucose and their main transport sugar
• Lactose


  Galactose-glucose, found only in mammalian milk and the main source of energy for infant mammals
• Main polysaccharides


  • Starch
  • Glycogen
  • Cellulose
• Starch


  • Insoluble plant storage polysaccharide, mixture of amylose and amylopectin
  • Amylose is poly-(1-4) glucose, long chain that coils into a helix
  • Amylopectin is poly 1-4 glucose with some 1-6 branches, more open structure
• Glycogen

  • Animal storage polysaccharide, similar to amylopectin but with more branches, can be broken down quickly
• Cellulose


  • Main component of plant cell walls, poly (1-4) glucose with β-glucose, forms straight rigid chains that form microfibrils
• Lipids


  Mixed group of hydrophobic compounds composed of C, H, O and sometimes P
• Triglycerides

  Fats or oils, made of glycerol and fatty acids

  
• Triglyceride formation

  One molecule of glycerol joins with three fatty acid molecules by ester bonds

  
• Triglyceride uses

  • Used for energy storage, insulation, waterproofing
• Saturated fatty acids


  No C=C double bonds, high melting point, solids (fats)
• Unsaturated fatty acids


  Have C=C double bonds, low melting point, liquids (oils)
• Phospholipids

  Similar to triglycerides but with a phosphate group instead of a fatty acid, have a polar hydrophilic head and non-polar hydrophobic tails
• Functions of proteins

  • Structure (e.g. collagen, keratin, actin)
  • Enzymes
  • Transport (e.g. haemoglobin, transferrin)
  • Pumps (e.g. Na+K+ pump)
  • Motors (e.g. myosin, kinesin)
  • Hormones (e.g. insulin, glucagon)
  • Receptors (e.g. rhodopsin)
  • Antibodies
  • Storage (e.g. albumins, casein)
  • Blood clotting (e.g. thrombin, fibrin)
  • Lubrication (e.g. glycoproteins)
  • Toxins (e.g. cholera toxin)
  • Antifreeze (e.g. glycoproteins)
• Amino acids


  Made of C, H, O, N, S, contain both an amino group and an acid group

  
• Amino acid structure


  • Central carbon atom with H, amino group, carboxyl group, and variable R group

  
• Protein synthesis occurs in ribosomes and requires an RNA template
• Protein structure levels


  • Primary (sequence of amino acids)
  • Secondary (α-helix, β-sheet)
  • Tertiary (overall 3D structure)
  • Quaternary (multiple polypeptide chains)

  
• Tertiary structure is held together by bonds between R-groups, including hydrogen bonds, ionic bonds, and disulfide bridges
• β-sheet

  The polypeptide chain zig-zags back and forward forming a sheet of antiparallel strands, held together by hydrogen bonds