biological molecules OCR notes

notes on chapter 7 biological molecules with diagrams

HideShow resource information
Preview of biological molecules OCR notes

First 477 words of the document:

Biological Molecules:
Hydrogen bonds occur between the slightly positive (+) hydrogen of one molecule and the slightly
negative (-) oxygen of another molecule, this type of bonding is weaker than covalent bonds, but a
lot of them can make a molecule very strong.
Latent heat of evaporation:
A lot of energy is needed to change water from a liquid to a gas. When sweat lies on your skin, the
water in the sweat absorbs heat energy from the body as it evaporates, the heat needed to do this
is called the latent heat of evaporation it's the major cooling mechanism. It also helps to cool plant
leaves in hot climates as water evaporates from the surface of the Mesophyll cells inside them.
Specific heat capacity:
Water has a high heat capacity because when you heat water more of the energy is used to break
the hydrogen bonds between molecules and there is less energy available to raise the temperature
by very much. Because we are mostly water we use this property well and your body does not
change temperature quickly, large changes in external temperature do not affect us by much. For
marine organisms this makes their external environment very stable, and it takes a lot of energy to
change the temperature in a pond or in the sea.
Good solvent:
Water is a good solvent because it is slightly charge, this attracts other charged molecules or ions to
it, the molecules and ions spread between the water molecules. Water is also polar substance,
meaning that only polar molecule can dissolve into it. Most metabolic reactions will only take place in
Water molecules in its liquid state are pulled close together by hydrogen bonds, and this makes it
very dense as the molecules are closer together. Water in its solid form is less dense because the
hydrogen bonds push the molecules apart; this makes ice float on water. This is also good because in
winter in a pond or lake not all the water will freeze and the water that does will rise to the top
leaving everything underneath all right and not all the water will freeze. Most living organism which
contains water have a density close to water, this makes it easier for them to swim.
Surface tension:
Water molecule stick together (cohesion), in water each molecule is attracted to all the other
molecules around it, but on the surface the uppermost molecules only have the other molecules
below not above, so they are pulled down, this creates a strong layer on the surface of the water
and small animals are able to walk on without difficulty.

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

Proteins are substances whose molecules are made up of amino acids, linked together in long chains.
All amino acids are made up of a central Carbon atom, which can have up to four bonds, its bonded
with a hydrogen (-H), bonded with a ­Carboxyl (-COOH) group, and an ­amino (-NH) group, and an
R group, which can be a whole range of different groups and is shown with the letter R.…read more

Page 3

Preview of page 3

Here's a taster:

Proteins are made up of lots of amino acids bonded together with peptide bonds and can therefore
be called polypeptides.
Primary Structure:
The primary structure of a protein is the amino
acid sequence of the polypeptide chain, it is
held together by covalent or peptide bonds and
disulphide bonds. The primary structure of a
protein is determined by the gene
corresponding to the protein, a specific
sequence of nucleotides in DNA s transcribed
into mRNA, which is read by the ribosome in
translation.…read more

Page 4

Preview of page 4

Here's a taster:

In haemoglobin, one of the beta polypeptide chains wind sit self around a little group of atoms with
with an iron ion (Fe²+) at the centre. In haemoglobin the structure is curled up into a ball forming a
globular protein. Enzymes are also globular proteins.In some proteins like collagen its shape is long
and thin. This makes Collagen a fibrous protein.…read more

Page 5

Preview of page 5

Page 6

Preview of page 6

Here's a taster:

Quaternary structure:
A haemoglobin molecule is made p of 4 polypeptide chains
these four chains fit together to make the complete
haemoglobin molecule. It is a globular protein. The shape they
produce is the quaternary structure of the protein. This shape
is held together by the same kind of bonds in tertiary structure.
The name quaternary doesn't refer to the four polypeptide
chains but it refers to the fourth level of structure.…read more

Page 7

Preview of page 7

Here's a taster:

Comparison of globular and fibrous proteins:
Globular proteins: enzymes, haemoglobin, antibodies, transporters in cell membranes, some
hormones e.g. insulin.
Fibrous Proteins: Keratin, Collagen, Elastin.
Primary structure:
Globular proteins: very precise, usually made up of a non-repeating sequence of amino acids
forming a chain that is always the same length.
Fibrous Proteins: often made up of a repeating sequence of amino acids and the chain can be of
varying length.
Globular proteins: often soluble though some e.g.…read more

Page 8

Preview of page 8

Here's a taster:

Are substances made up of only Carbon Hydrogen and Oxygen, the general formula of
carbohydrates is CnH2nOn, carbohydrates include sugars, starches and cellulose. Sugars are
Always soluble in water, and they taste sweet. Starches and cellulose, which are both examples of
polysaccharides, are insoluble in water and
do not taste sweet.
Are made up of only one sugar glucose,
fructose and Galactose are examples of
Glucose is a hexose sugar which means that it has six carbons.…read more

Page 9

Preview of page 9

Here's a taster:

If you link thousands of glucose molecules with glycosidic bonds forms the carbohydrate Amylose
which is found in starch. Starch is insoluble and metabolically inactive which means that it won't
interfere with the reactions going on around it and it doesn't affect water potential. In amylase the
molecules coil in a long spiral, this makes them very compact and lots of starch can be stored in a
small space.…read more

Page 10

Preview of page 10

Here's a taster:

Monosaccharide from which it is formed:
Amylose: -Glucose
Cellulose: - glucose
Glycogen: -Glucose
Type(s) of glycosidic bond:
Amylose: - 1-4
Cellulose: - 1-4
Glycogen: -1-4 with 1-6 at the branches
Overall shape of the molecule:
Amylose: helix
Cellulose: straight chain
Glycogen: branched and slightly coiled
Hydrogen bonding within or between molecules?
Amylose: hydrogen bonds between sugar units in the chain
Cellulose: hydrogen bonds between sugar units in different chains
Glycogen: some hydrogen bonds between sugar units in the chain
Solubility in water:
Amylose: insoluble
Cellulose:…read more


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all resources »