Task up of chains of amino acids, with

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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, with peptide bonds separating each amino acid. It
consists of four polypeptide chains, two alpha (?) chains and two beta (?) chains.


The two types of secondary structure found in proteins are
the alpha-helix (?) or the
Beta-pleated (?)
sheet. These structures both involve polypeptide chains, however, in this
instance they form different shapes, these are held together by weak
intermolecular forces 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 stabilising the
structure in each haemoglobin chain. The haem molecule is involved in the
bending of the haemoglobin, creating the 3D structure of the chain. As
haemoglobin is a globular protein, this means that ball-like structures tend to
be 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 contain more than one polypeptide
chain which can be held together by hydrogen, ionic and disulfide bonds. Haemoglobin
contains four polypeptide chains, and each of these contain a haem group
(prosthetic group). Also, there is an iron ion (Fe²?) which is where the oxygen binds
due to iron’s high affinity for oxygen. Haemoglobin can be found in the red
blood cells in the circulatory system.

How The Protein is Able to Maintain
its Structure:

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

Hydrophilic Interaction – These are found on the
outside of the 3D structure of haemoglobin, and they are hydrophilic, meaning
that they attract water. These amino acids contain polar side chains, meaning
they are charged.

Overall, this means that haemoglobin is water soluble.

Disulfide Bridges – These are formed between two
sulfur atoms found on two opposite cysteine amino acids, when this happens,
each cysteine 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 found on different amino acids. For this
to occur, the oxygen or nitrogen must have a lone pair of electrons in order to
form a hydrogen bond. Then, the lone pair of electrons will be shared by the
oxygen or nitrogen atom on one amino acid and the hydrogen atom on the the
amino acid.

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

Function of

Haemoglobin is found in the red blood cells, where it carried
oxygen through the repiratory 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

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

Date Accessed: 16/01/18

Date Accessed: 16/01/18





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