Biochemical molecules intro plus water.ppt

biological molecules AS level

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!!
Rabbit
Right to left
•O – red
•C – black
•H – white
•N – blue
•Ca – silver
•P - purple
Bush
Right to left
•O – red
•C – black
•H – white
•N – blue
•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. 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. Water
It’s kinda weird – but very useful
Intro to water
and its properties

11. The weirdness of water
H
2O, CH
4, NH
3
•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. 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. 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. 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