Ch.3 The Chemistry of Life

Elements found in living organisms: The most frequently occurring elements in living things are: Carbon (19%) Oxygen (65%) Hydrogen (10%) Nitrogen (3%)

Foundation of organic molecules Elements Some Functions Carbon Foundation of organic molecules Hydrogen Ions used in photosynthesis, cell respiration, active transport Oxygen Aerobic respiration, oxidation reactions for ATP ADP Nitrogen Found in amino acids  proteins, forms of nitrogen include ammonium and nitrates

Water Molecule The two hydrogen atoms bond covalently with the oxygen atom; this creates polarity Hydrogen side is slightly positively charged while oxygen side is slightly negatively charged

Properties of Water Because of water’s polarity, water molecules interact with each other in interesting ways Some properties of water include Thermal properties Cohesive properties Solvent properties

Thermal Properties High Specific Heat – water can absorb or give off a great deal of heat without big temperature change This is important for living organisms b/c blood (which is mainly water and therefore stable in temperature) can carry heat to our extremities when cold

Thermal Properties High Heat of Vaporization – water absorbs a lot of heat when it evaporates This is important for living organisms b/c they can use it as a cooling mechanism when internal heat results in perspiration, then perspiration evaporates by using your body’s heat which cools you down

Cohesive Properties Water is cohesive meaning the molecules stick to each other This is important for living organisms b/c it allows plants to pull water up from their roots against gravity and for animals it allows some insects to ‘walk on water’

Solvent Properties Water is the Universal Solvent b/c it is polar and therefore other polar molecules like carbs, proteins, and DNA can dissolve in it This is important for living organisms b/c water is the medium for metabolic reactions Aqueous Solution Location Common Reactions Cytoplasm Fluid insides cells but outside organelles Glycolysis, protein synthesis Nucleoplasm Fluid inside nuclear membrane DNA replication, transcription Stroma Fluid inside chloroplast organelle in plants Light dependent rxns of photosynthesis Blood Fluid in arteries, veins, capillaries Exchange of gases (O2 and CO2), clotting

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