viewiop.blogg.se - Do alpha helices have a lot of hydrophobic amino acids

It is found in many diverse organisms and organs:

Collagen - found in bone, cartilage, tendons and ligaments for tensile strengthĬollagen is the most abundant protein in the animal kingdom.

These chains are linked by disulphide cross bridges – making the proteins very stable and strongįibrous proteins have Structural functions: Polypeptides form long chains running parallel to each other The 3D-shape of globular proteins is critical to their function – slight changes can have radical effects – eg in sickle cell anaemia one amino acid change causes a shape change in the molecule that in turns reduces the ability of haemoglobin to bind to oxygen and changes the shape of the whole red blood cell from a biconcave disk to a sickle shape. When haemoglobin is bound to oxygen it is called oxyhaemoglobin and the colour changes from purplish red to bright red Human haemoglobin has four polypeptide chains and four haem groups and can therefore carry 4 x O 2 molecules The Hydrophilic R-groups are arranged around the outside of the molecule which allows Haemoglobin to mix with the watery medium inside red blood cellsĪttached to each polypeptide chain is a prosthetic HAEM group with an Fe2+ ionĮach Fe2+ ion can combine with one O 2 molecule The precise 3D-shape of the Haemoglobin molecule is absolutely critical to it's Oxygen-carrying function Haemoglobin has a quaternary structure made up of 4 separate polypeptide chains:Ģ identical alpha -chains with 141 amino acids eachĢ identical beta -chains with 146 amino acids eachĮach polypeptide chain is folded/coiled into a compact shape due to hydrophobic interactions between the (hydrophobic) R groupsĪll 4 polypeptide chains are linked to form a roughly spherical haemoglobin molecule

Haemoglobin - binds to oxygen to transport it around body.

Globular proteins have roles in metabolic reactions:

Only hydrophilic groups are exposed outside the molecule so globular proteins are soluble Hydrophobic groups point into centre of molecule away from water