Download Biochemical molecules

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
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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
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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