1. Biochemical molecules
An introduction

2. 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

3. Time to start thinking…….
What are you made of ?
(sugar and spice is not an acceptable answer)

4. Four types to look at Water Carbohydrates Lipids Proteins
Revise anything you know about all of these from GCSE!

5. 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?

6. 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?

7. 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

8. 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

9. Hydrogen atom

10. It’s kinda weird – but very useful
Water
It’s kinda weird – but very useful
Intro to water
and its properties

11. The weirdness of water H2O, CH4, NH3
All small, covalently bonded molecules but methane and ammonia are gases – water is a liquid! .

12. 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

13. Water – a polar molecule

14. Hydrogen bonding

15. 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

17. 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

18. 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

19. 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

20. 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

21. 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)

22. 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

23. 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.

24. 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

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