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!! Why does the bunny have so much more calcium than the 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

Turning the deceased into diamonds 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

It’s kinda weird – but very useful 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 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. Explanatory animation John Kyrk water – extension only

Water – a polar molecule

Hydrogen bonding

Entire website about water 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

Explanatory animation Good solvent 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 Explanatory animation

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.

Quiz on properties of water Has it stuck? P147 Question no. 4 (just write down the missing words) Answers page 252 Quiz on properties of water

Homework Revise all GCSE knowledge of carbohydrates, proteins and lipids, including the biochemical tests for sugars, starchs, proteins and lipids