Proteins

Proteins

Proteins consist of one or more chains of amino acids folded into a unique three-dimentional shape. The shape is determined by by up to four levels of structure(each level of structure determines the next):

• Primary structure: a proteins primary structure is the sequence of amino acids that make up its polypeptide chains.In order for a protein to carry out its specific function, it must contain the correct amino acids arranges in a precise order.
  
• Secondary structure: Is the coil into an alpha-helix or beta-pleated sheet by hydrogen bonding.
• Tertiary structure: Refers to the overall three-dimensional shape of a polypeptide chain.they are classified into two main groups depending on the basis of their tertiary structure:

Fibrous proteins consist of parallel polypeptide chains cross-linked at intervals of from long fibres or sheets. In globular proteins the polypeptide chains are tightly folded to form a spherical shape. Breaking down the tertiaty structure:denatiration. if the bons holding the proteins chape are broken, a proces called denaturation occurs. the polypeptide chains unravel and lose their specific shape,as a result they lose their specific function.Denaturation is nearly irreversible. It can be cause by:

1. changes in ph
2. salt concentration
3. temperature

• Quaternary structure: the association of polypeptide chains.Many proteins consist of more than one polypeptide chain bonded to each other. It refers to the way these polypeptide chains are arranged.