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Biochemical molecules An introduction How does this fit into the scheme? • F212 – June paper – Module 1 (of 3) – Biological molecules • 2.1.1 Biological molecules • 2.1.2 DNA • 2.1.3 Enzymes We will actually teach this in the order; molecules, enzymes then DNA You will see that in your exam question booklet they are in this order Time to start thinking……. • What are you made of ? • (sugar and spice is not an acceptable answer) Four types to look at • • • • Water Carbohydrates Lipids Proteins Revise anything you know about all of these from GCSE! Elements involved • The big three – C, H and O • Others that turn up frequently – N, P and S • There are small amounts of others too e.g. minerals – Ca, K, Na, Cl, Mg • Can you name any instances we have met already where these elements are involved? Colouring in!! Bush Right to left • O – red • C – black • H – white • N – blue • P - purple Rabbit Right to left • O – red • C – black • H – white • N – blue • Ca – silver • P - purple Why does the bunny have so much more calcium than the Plant that there is enough to make a stripe on the diagram? Components of a human (1968) Take one 156lb human • 100lbs oxygen • 28lbs carbon • 15lbs hydrogen • 4.6lb nitrogen • 2.3lb calcium • 1.6lb phosphorous • 8.5oz potassium • 6oz sulphur • 3.7oz sodium • 3.7oz chlorine • • • • • • • • • 1.25oz magnesium 0.15oz iron 1.9g zinc 0.2g copper 0.02g manganese 0.015g molybdenum some cobalt some selenium and traces of others • Worth about 5 shillings Carbon based life • Where is carbon on the periodic table? • How many electrons does it have in its outer shell? • How many covalent bonds can it form? • Being able to form 4 covalent bonds carbon can be the basis of complex molecules – long chains, rings and these can include single, double or triple bonds. This molecular complexity is vital to life. Turning the deceased into diamonds Hydrogen atom Water It’s kinda weird – but very useful Intro to water and its properties The weirdness of water H2O, CH4, NH3 • All small, covalently bonded molecules but methane and ammonia are gases – water is a liquid! . Hydrogen bonding in water Explanatory animation • The polar nature of the covalent bonds that hold water together, and the hydrogen bonds between the water molecules, explain the properties of water – that make it so useful to life. John Kyrk water – extension only Water – a polar molecule Hydrogen bonding Properties of water • Liquid at biological temperatures – high latent heat • Good solvent • Good thermal buffer - high specific heat capacity • High surface tension • Most dense at 4°C – ice floats • These properties can all be explained due to the polar nature of water and the H bonds • Also, in reactions it can be used e.g. as a source of hydrogen Entire website about water Liquid at room temperatures • Organisms can interact with it, live in and on it, use it as a solvent etc. which they couldn’t if it were a gas. • As a liquid it is incompressible • Therefore it can be used for support – e.g. turgor pressure in plants High Latent Heat • It takes a lot of energy to change the physical state of water, therefore it is unlikely to change, so it is a stable environment for organisms to live in – it is less likely to evaporate or freeze than other liquids • This also means that the evaporation of water can be used as an effective cooling mechanism e.g. panting and sweating Good solvent Explanatory animation • As a solvent of polar molecules water can dissolve most biological molecules – except lipids • Therefore reactions can easily take place within water • Organisms can therefore use water as the basis of their cytoplasm • In multicellular organisms it can also be used as a transport medium e.g. it is the basis of plasma and sap High specific heat capacity • It takes a lot of energy to change the temperature of water • Therefore it is a stable environment to live in • Also internal body temperatures are less likely to change High surface tension • Allows organisms to live on the surface of water e.g. pond skaters • Is also important in capillary action e.g. in the xylem (cohesion) Most dense at 4°C • Ice (solid water) floats on liquid water • This insulates the lower levels of a pond so the entire pond doesn’t freeze • It provides a habitat for penguins. • It sets up currents in the water which, particularly in the sea, circulates nutrients Reactant • Is used in hydrolysis reactions to split macromolecules into smaller units by adding water. • And the reverse - joining monomers to form polymers by the removal of water – condensation polymerisation. • Is a source of hydrogen for the reactions of photosynthesis. Has it stuck? Quiz on properties of water • P147 Question no. 4 (just write down the missing words) • Answers page 252 Homework • Revise all GCSE knowledge of carbohydrates, proteins and lipids, including the biochemical tests for sugars, starchs, proteins and lipids