Biological Compounds

• Inorganic ions


  Occur in solution in the cytoplasm and body fluid of organisms, some in high concentrations and others in very low concentrations
• Inorganic ions required for plant growth and development

  • Nitrate ions
  • Calcium ions
  • Phosphate ions
  • Magnesium ions
  • Iron ions
• Nitrate ions


  Required to make DNA and amino acids
• Calcium ions


  Needed to form calcium pectate for the middle lamellae
• Phosphate ions


  Required to make ADP and ATP
• Magnesium ions


  Needed to produce chlorophyll
• Iron ions


  A component of haemoglobin which is an oxygen carrying molecule in red blood cells
• Water


  • It is a polar molecule due to uneven distribution of charge within the molecule
  • It is a metabolite in metabolic reactions such as condensation and hydrolysis
  • It is a solvent in which many metabolic reactions occur
  • It has a high heat specific capacity meaning that a lot of energy is required to warm water up therefore minimising temperature fluctuations in living things therefore it acts as a buffer
  • It has a relatively large latent heat of vaporisation, meaning evaporation of water provides a cooling effect with little water loss
  • Strong cohesion between molecules enables effective transport of water in tube like transport cells as the strong cohesion supports columns of water, as a result of strong cohesion the surface tension at the water-air boundary is high
• Carbohydrates


  Molecules which consist only of carbon, hydrogen and oxygen and they are long chains of sugar units called saccharides
• Types of saccharides


  • Monosaccharides
  • Disaccharides
  • Polysaccharides
• Glycosidic bonds


  Formed in condensation reactions to join monosaccharides to form disaccharides and polysaccharides
• Monosaccharides


  Small organic molecules used as building blocks of complex carbohydrates
• Monosaccharides


  • Glyceraldehyde
  • Ribose
  • Glucose

  
• Glucose


  A monosaccharide containing six carbon atoms, it is the main substrate for respiration and therefore of great importance. It has two isomers - alpha and beta glucose.

  
• Disaccharides


  • Maltose
  • Sucrose
  • Lactose
• Polysaccharides


  • Glycogen
  • Starch
  • Cellulose
• Glycogen


  The main energy storage molecule in animals, formed from many molecules of alpha glucose joined together by 1,4 and 1,6 glycosidic bonds. It has a large number of side branches meaning that energy can be released quickly. It is a relatively large but compact molecule thus maximising the amount of energy it can store.

  
• Starch


  Stores energy in plants and it is a mixture of two polysaccharides called amylose and amylopectin. Amylose is an unbranched chain of glucose molecules joined by 1,4 glycosidic bonds, as a result of that amylose is coiled and thus it is a very compact molecule meaning it can store a lot of energy. Amylopectin is branched and is made up of glucose molecules joined by 1,4 and 1,6 glycosidic bonds, due to the presence of many side branches it is rapidly digested by enzymes therefore energy is released quickly.
• Cellulose


  A component of cells wells in plants and it's composed of long, unbranched chains of beta glucose which are joined by glycosidic bonds. Microfibrils are strong threads which are made of long cellulose chains joined together by hydrogen bonds and they provide structural support in plants cells.
• 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 is lightweight but strong and is used to form the exoskeletons of insects.

  
• Lipids


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


  • Saturated lipids
  • Unsaturated lipids
• Saturated lipids


  Don't contain any carbon-carbon double bonds, found in animal fats. Too much saturated fat can increase the cholesterol levels in blood thus increasing the risk of coronary heart disease.
• Unsaturated lipids


  Contain carbon-carbon double bonds, found in plants. Unsaturated fats are healthy as they provide essential fatty acids.

  
• Triglycerides


  Lipids made of one molecule of glycerol and three fatty acids joined by ester bonds formed in condensation reactions. There are many different types of fatty acids, they vary in chain length, presence and number of double bonds. Triglycerides are used as energy reserves in plant and animal cells.

  
• Phospholipids


  One of the fatty acids of a triglyceride is substituted by a phosphate-containing group. Phosphate heads are hydrophilic and the tails are hydrophobic and as a result phospholipids form micelles when they are in contact with water as heads are on the outside as they are attracted to water and tails are on the inside as they move away from water.

  
• Amino acids


  The 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. Amino acids are joined by peptide bonds formed in condensation reactions.
• Dipeptide


  Contains two amino acids
• Polypeptide


  Contains three or more amino acids
• Levels of protein structure

  • Primary structure
  • Secondary structure
  • Tertiary structure
• Primary structure


  The order and number of amino acids in a protein
• Secondary structure


  The shape that the chain of amino acids chains - either alpha helix or beta pleated sheet. The shape is determined by the type of bonding present such as hydrogen bonding, ionic bonds and disulphide bridges.
• Tertiary structure


  The 3D shape of the protein, it can be globular of fibrous. Globular proteins such as enzymes are compact whereas fibrous proteins such as keratin are long and thus can be used to form fibres.
• Collagen


  A fibrous protein of great strength due to presence of both hydrogen and covalent bonds in the structure. 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 which connect muscles to bones.
• Haemoglobin


  A water soluble globular protein which consists of two beta polypeptide chains and a haem group. It carries oxygen in the blood as oxygen can bind to the haem (Fe2+) group and oxygen is then released when required.