Lipids, Water and Inorganic Ions

• Phosphate ions are a component of DNA, ATP, NADP, and cAMP.
• Phosphate ions are involved in the propagation of action potentials in neurons.
• To test for lipids in a sample, dissolve solid samples in ethanol, add an equal volume of water and shake, and a positive result is indicated by a milky white emulsion forming.
• Water is significant to living organisms as a metabolite, solvent for chemical reactions, has high specific heat capacity, high latent heat of vapourisation, and enables organisms to avoid fluctuations in core temperature.
• Each haemoglobin molecule has four haem groups.
• The haem group in haemoglobin has a binding site to transport one molecule of O2 around the body in the bloodstream.
• Phospholipids have 2 fatty acids and 1 phosphate group attached, have a hydrophilic head and a hydrophobic tail, and are primarily used in membrane formation.
• Hydrogen ions interact with H-bonds and ionic bonds in the tertiary structure of proteins, which can cause them to denature.
• Iron ions bind to the porphyrin ring to form the haem group in haemoglobin.
• Hydrogen ions in the body have a high concentration, which results in a low (acidic) pH.
• Sodium ions are involved in co-transport for the absorption of glucose and amino acids in the lumen of the gut.
• Water is a polar molecule due to the electronegativity of oxygen, which attracts the electron density in the covalent bond more strongly, forming O- (slight negative charge) and H+ (slight positive charge).
• Triglycerides have 3 fatty acids attached, are entirely hydrophobic, and are primarily used as a storage molecule, as oxidation releases energy.
• Triglycerides form through a condensation reaction between one molecule of glycerol and three fatty acids, forming ester bonds.
• Unsaturated fats contain C=C double bonds, have 'kinked' molecules with fewer contact points, have a lower melting point, and are found in plant oils.
• Saturated fats contain only single bonds, have straight-chain molecules with many contact points, have a higher melting point, and are found in animal fats.
• Triglycerides have a high energy:mass ratio, are insoluble hydrocarbon chains, are slow conductors of heat, and are less dense than water, providing buoyancy for aquatic animals.
• Phospholipids are amphipathic molecules with a glycerol backbone attached to two hydrophobic fatty acid tails and one hydrophilic polar phosphate head.
• Phospholipids form a phospholipid bilayer in water, are a component of membranes, and their tails can splay outwards for waterproofing.
• Both phospholipids and triglycerides have a glycerol backbone, may be attached to a mixture of saturated, monounsaturated & polyunsaturated fatty acids, contain the elements C, H, O, and are formed by condensation reactions.