TOPIC 3.1 Chemical Elements and Water

3.1.1 Most Frequently Occurring Elements Oxygen - 65% Carbon - 19% Hydrogen - 10% Nitrogen - 3% Carbohydrates and lipids composed of C, H and O Proteins composed of C, H, O, N and some amino acids contain S (cysteine)

Bonds Between Atoms Element = pure substances that cannot be broken down further Compound = two or more elements which are chemically combined Covalent bonds = atoms share electrons ex. H 2 O Ionic bonds = atoms gain or lose electrons ex. NaCl (the atoms become + or – ions) Hydrogen bonds = weak polar bonds ex. Between the bases in DNA Peptide bonds = bonds between amino acids to form polypeptides

3.1.2 Other Elements Needed by Living Organisms Sulfur (sulphur) Calcium Phosphorus Sodium Iron

3.1.3 One Role for Each Element in ElementRole in ProkaryotesRole in PlantsRole in Animals SulfurChemosynthesis- using sulfur as their source of energy Produce amino acids which are part of some enzymes and proteins PhosphorusPart of ATP and DNA CalciumNeeded to maintain cell structure and movement Co-factor in some enzymes Component of cell walls and cell membranes Co-factor in some enzymes Makes our bones hard and strong Needed in release of neurotransmitters to transmit nerve impulses Co-factor in some enzymes IronIn cytochromes Needed for the formation of chlorophyll Component of hemoglobin in red blood cells- needed to transport oxygen SodiumIndirectly helps move flagellum In some plants helps bind CO 2 for photosynthesis Involved in action potential in neurons- Na/K pump Co-transport of glucose

3.1.4 Draw and Label Diagram of Water Molecules Hydrogen bonds are weak polar bonds

3.1.5 Thermal, Cohesive and Solvent Properties of H 2 O Cohesive Properties = the attraction forces between molecules of the same kind – Used for transport in plants (capillary action) Thermal properties = high specific heat and high heat of vaporization – High specific heat = H 2 O requires a lot of E to warm up and gives off a lot of E when cooled down (blood can carry heat to colder places in our body; your nose gets red when you are cold) – High heat of vaporization = H 2 O requires a lot of E to change from a liquid to a gas (sweating- evaporation has a cooling effect)

Solvent properties = water is polar and will dissolve many polar solutes – Important for transport In plants water transports minerals and sugars In animals blood transports oxygen, carbon dioxide, glucose, amino acids, fibrinogen (important protein involved in blood clotting) – Important medium for metabolic reactions In plants – fluid inside chloroplast for light-independent reactions of photosynthesis In animals – fluid inside nuclear membrane where DNA replication and transcription take place