Biological molecules

• The four key inorganic ions in living organisms are Magnesium ions (Mg 2+ ), Iron ions (Fe 2+ ), Calcium ions (Ca 2+ ), and Phosphate ions (PO 4 3- ).
• The positive result of an emulsion test is the formation of a white, cloudy emulsion.
• The iodine-potassium iodide test for starch involves adding iodine-KI solution, observing a colour change from orange to blue-black in the presence of starch.
• The positive result of a biuret test is a colour change from pale blue to purple.
• The emulsion test for fats and oils involves adding ethanol to the sample, allowing the mixture to settle, adding an equal volume of water, and recording any observations.
• Mg 2+ is used to produce chlorophyll in plants.
• Fe 2+ is found in haemoglobin and is involved in the transport of oxygen in animals.
• The high surface tension of water is important for organisms as it enables the transport of water and nutrients through plants stems and small blood vessels in the body, and allows small insects to 'walk' on water.
• Monosaccharides are simple sugars with the general formula C n (H 2 O) n.
• Water's high surface tension is due to the ordered arrangement and cohesion of molecules at the surface of water.
• Water is a polar universal solvent that enables chemical reactions to take place within cells, the transport of materials in the plasma and the removal of metabolic waste.
• Water's high latent heat of vaporisation is important for organisms as it has a cooling effect in homeostasis.
• Deoxyribose is a monosaccharide.
• α-glucose is a monosaccharide.
• β-glucose is a monosaccharide.
• Examples of monosaccharides include Glyceraldehyde, Ribose, Deoxyribose, α- and β- glucose, Fructose, Galactose.
• PO 4 3- is used to produce ADP and ATP in living organisms.
• Ca 2+ is used to strengthen tissues such as bones and teeth in animals and cell walls in plants.
• Water is a polar molecule because O is more electronegative than H, attracting the electron density in the covalent bond more strongly, forming δ- O and δ+ H.
• Weak intermolecular forces of attraction form between a lone pair on a δ- O and a δ+ H on an adjacent molecule.
• A metabolite is a molecule formed or used in metabolic reactions.
• Water is a reactant in photosynthesis and hydrolysis reactions and a product in aerobic respiration and condensation reactions.
• Water acts as a temperature buffer, enabling endotherms to resist fluctuations in core temperature and to maintain optimum enzyme activity.
• The Biuret test involves adding an equal volume of the sample to be tested and NaOH, a few drops of dilute copper (II) sulfate solution, and observing the colour of the resulting solution.
• Globular proteins are long polypeptide chains, folded in parallel, with little tertiary/quaternary structure aside from cross-linkages for strength, making them insoluble and good for structural roles.
• The Benedict’s test for non-reducing sugars involves hydrolysing non-reducing sugars with an equal volume of dilute HCl, heating in a boiling water bath for 5 minutes, adding NaHCO 3 to neutralise the acid, and re-testing the resulting solution with Benedict’s reagent, observing the colour of the precipitate formed.
• The positive result for reducing sugars involves a colour change from green to yellow to orange to brown to a brick red depending on the quantity of reducing sugar present.
• Globular proteins are spherical, compact, highly folded with complex tertiary/quaternary structures, are water-soluble, and have hydrophilic R groups facing outwards and hydrophobic R groups facing inwards, making them metabolic roles, such as enzymes.
• The Benedict’s test for reducing sugars involves adding an equal volume of the sample being tested and Benedict’s reagent, heating the mixture in an electric water bath at 100°C for 5 minutes, and observing the colour of the precipitate formed.
• A reducing sugar has a free aldehyde or ketone functional group so can act as a reducing agent, while a non-reducing sugar does not have a free aldehyde or ketone functional group so it cannot act as a reducing agent.
• The positive result for non-reducing sugars involves a colour change from green to yellow to orange to brown to brick red depending on the quantity of non-reducing sugar present.
• Phospholipids form a phospholipid bilayer in water, are components of cell membranes, and their tails splay outwards for waterproofing, as seen in the skin.
• Saturated fats have no C=C bonds, are solid at room temperature due to strong intermolecular forces, and are used for energy storage.
• Chitin consists of many β-glucose molecules (with amino acid side chains) joined by β-1,4-glycosidic bonds.
• Linear polysaccharide found in the exoskeletons of insects and crustaceans as well as fungal cell walls is called chitin.
• A phospholipid is a type of lipid formed by the condensation of one molecule of glycerol, two molecules of fatty acid and a phosphate group.
• Triglycerides have a high energy-to-mass ratio, are insoluble in water, are slow conductors of heat, and are less dense than water, making them useful for energy storage, thermal insulation, and buoyancy.
• Unsaturated fats have one or more C=C bonds, are liquid at room temperature due to weak intermolecular forces, and are used for energy storage.
• Monounsaturated fats have one C=C bond, are liquid at room temperature, and are used for energy storage.
• The structure of phospholipids consists of a glycerol backbone attached to two hydrophobic fatty acid tails and one hydrophilic polar phosphate head.