Task 2 – P3M2Structureand Function of HaemoglobinPrimaryStructure: This is haemoglobin at the simplest level, it is made up ofchains of amino acids, in which peptide bonds separating each amino acid.
Itconsists of four polypeptide chains, two alpha (?) chains and two beta (?) chains.SecondaryStructure: The two types of secondary structure found in proteins arethe alpha-helix (?) or theBeta-pleated (?)sheet. These structures both involve polypeptide chains, however, in thisinstance they form different shapes, these are held together by weakintermolecular forces called hydrogen bonds. Hydrogen bonds can be foundbetween the N-H and C=O groups, giving it a more stable structure.
TertiaryStructure: This is the main bonding which is involved in stabilising thestructure in each haemoglobin chain. The haem molecule is involved in thebending of the haemoglobin, creating the 3D structure of the chain. Haemoglobinis a globular protein, this means that ball-like structures are formed, wherethe hydrophobic part is towards the centre and the hydrophilic part is towardsthe edges, this means that they are water soluble. Quaternary Structure: These are proteins that contain more than one polypeptidechain which are held together by hydrogen, ionic and disulfide bonds. Haemoglobinhas four polypeptide chains, and all of these contain a haem group.
Also, thereis 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 Maintainits Structure:Hydrophobic Interaction – These weak bonds arefound inside of the 3D structure of haemoglobin, and they form between Rgroups, which only contain hydrogen and carbon. These interactions arehydrophobic, meaning they repel water. These amino acids contain non-polar sidechains, meaning they’re not charged.
Hydrophilic Interaction – These are found on theoutside of the 3D structure of haemoglobin. They are hydrophilic, this means thatthey attract water. These amino acids contain polar side chains, meaning they arecharged.Overall, this means that haemoglobin is soluble in water.
Disulfide Bridges – These are formed between twosulfur 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 oxygenor a nitrogen atom and a hydrogen atom found on different amino acids. For thisto occur, the oxygen or nitrogen must have a lone pair of electrons in order toform a hydrogen bond. Then, pair of electrons will be shared by the nitrogen orthe oxygen atom on one amino acid and the hydrogen atom on the the amino acid.Ionic Bonds – These are formed betweenoppositely charged variable (R) groups which contain a carboxylic acid (-COOH)and an amine (-NH?) group.
Thesebonds are stonger than hydrogen bonds, however, they can be broken by a changein temperature or pH. Function ofHaemoglobin:Haemoglobin is found in the red blood cells, where it carriedoxygen through the repiratory system and around the rest of the body. It is aglobular protein which shows a quaternary structure, and it also contains otherstructures 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 foroxygen.