Task means that they are water soluble.

Task 2 – P3

and Function of Haemoglobin

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This is haemoglobin at the simplest level, it is made up of
chains of amino acids, in which peptide bonds separating each amino acid. It
contains four polypeptide chains, two alpha (?) and two beta (?)s.


The two types of secondary structure found in proteins are
the alpha-helix (?) or the
Beta-pleated (?)
sheet. The structures mentioned both include polypeptide chains, however,
in this instance they are able to construct different shapes, these are secured
by weak intermolecular forces which are called hydrogen bonds. Hydrogen bonds
can be found between the N-H and C=O groups, giving it a more stable structure.


This is the main bonding which is involved in upholding the
structure in each haemoglobin chain. The haem molecule is involved in the
bending of the haemoglobin, creating the 3D structure of the chain. Haemoglobin
is a globular protein, this means that ball-like structures are formed, where
the hydrophobic part is towards the centre and the hydrophilic part is towards
the edges, this means that they are water soluble.

Quaternary Structure:

These are proteins that numerous polypeptide chains and these
are held together by hydrogen, ionic and disulfide bonds. Haemoglobin has four
polypeptide chains, and all of these contain a haem group. Also, there is an
iron ion (Fe²?)
this is where the oxygen binds due to iron’s high affinity for oxygen.
Haemoglobin it located in the red blood cells in the circulatory system.

How The Protein is Able to Maintain
its Structure:

Hydrophobic Interaction – These weak bonds are
found inside of the 3D structure of haemoglobin, and they form between R
groups, and these groups only contain hydrogen and carbon. These interactions
are hydrophobic, meaning they repel water. These amino acids are not charged
due to the fact that they contain non-polar side chains.

Hydrophilic Interaction – These are found on the
outside of the 3D structure of haemoglobin. They are hydrophilic, this means that
they attract water. These amino acids  are charged due to the fact that they contain
polar side chains.

Overall, this means that haemoglobin is soluble in water.

Disulfide Bridges – These are formed between two
sulfur atoms found on two opposite cysteine amino acids, when this happens,
each one loses a H?.
These are exceptionally strong bonds and can only be broken by reducing agents,
not by things like pH temperature.   

Hydrogen Bonds – These can form between an oxygen
or a nitrogen atom and a hydrogen atom which are found on different amino
acids. For this to occur, the oxygen or nitrogen needs to have a lone pair of
electrons in order to form a hydrogen bond. Then, the pair of electrons will be
shared by the nitrogen or the oxygen atom on one amino acid and the hydrogen
atom on the amino acid.

Ionic Bonds – These are formed between
oppositely charged variable (R) groups which contain a carboxylic acid (-COOH)
and an amine (-NH?) group. These
bonds are stonger than hydrogen bonds, however, they can be broken by a change
in temperature or pH. 

Function of

Haemoglobin is located in the red blood cells, where it
carried oxygen through the respiratory system and around the rest of the body.
It is a globular protein which shows a quaternary structure, and it also
contains other structures such as haem groups and iron ions. This allows oxygen
to bind to it, and this is possible because the iron ion give haemoglobin a
high affinity for oxygen.

References: https://image.slidesharecdn.com/06-hbbyasif-161017032416/95/hemoglobin-structure-15-638.jpg?cb=1476674684  Date Accessed: 16/01/18

http://www.biotopics.co.uk/as/haemoglobinproteinstructure.html  Date Accessed: 16/01/18

https://alevelnotes.com/Protein-Structure/61  Date Accessed: 16/01/18