Task amino acids contain non-polar side chains, meaning they’re

Task 2 – P3
M2

Structure
and Function of Haemoglobin

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Primary
Structure:

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
consists of four polypeptide chains, two alpha (?) chains and two beta (?) chains.

Secondary
Structure:

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.

Tertiary
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. 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 contain more than one polypeptide
chain which 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 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 are
found 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’re not charged.

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 contain polar side chains, meaning they are
charged.

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 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, pair of electrons will be shared by the nitrogen or
the oxygen 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 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:

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
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

 

 

 

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