- Created by: Fredcatley
- Created on: 29-11-18 11:32
- Building block of a protein=amino acids
- Amino acids are monomers that are joined in a sequence to form a protein
- The sequence of the amino acids determines the protein+its function
- Structure of an amino acid: amino group, carboxyl group, residual group
- Each of the 20 different amino acids have a different residual group
Forming peptide bonds
- A protein is a polymer of amino acids
- Two amino acids are joined together by a condesation reaction to form a peptide bond
- The bond can be broken by hydrolysis, which involves adding water.
- When a larger chain of amino acids is formed=polypeptide
Levels of protein structure: primary+secondary
- Primary structure: seqeunce, type+number of amino acids in the chain. The structure+amino acids present determine the protein's function.
- Secondary structure:
- Chain takes a particular shape by folding or coiling as a result of the bonds formed between amino acids. Order of amino acids determines where bonds are formed=what shape occurs.
- Two forms of secondary folding: alpha helix and the beta pleated sheet. Alpha helix=held in place by H bonds between amino acids from different parts of the chain. Beta pleated sheet=folds in a concertina like way, H bonds connect to adjacent pleated sheet.
Levels of protein structure: tertiary- gobular+fib
- Tertiary structure: 3D shape of protein molecule=further coiled or twisted into a more complex shape. Two types of tertiary structure: globular and fibrous
- Globular: when protein folds to form 3D shape=important in metabolic processes=enzymes=have specific active site for subsrate to bind too
- Fibrous: protein twists into a long thin structure, has important structural roles: keratin-hair, collagen in skin.
Levels of protein structure: tertiary,types of bon
- Globular and fibrous proteins have a no.of different type of bonds to stabilise the molecule:H bonds, Ionic bonds, hydrophobic interations and disuphide bonds.
- H bond: attraction between slight + charge of a group and slight - charge of another
- Ionic bond: attraction between + charged R group of an amino acid and - charged R group of another.
- Hydrophobic interaction: association between hydrophobic R groups of amino acids (where H2O is excluded).
- Disulphide bond: Covalent bond between sulfur atoms of two R groups.
Levels of protein structure: quaternary
- Some proteins=made of more than 1 polypeptide chain
- Two or more chains are held together+function as a whole
- Protein will not function unless all subunits are together
- Haemoglobin: quaternary structure+haem prothestic group (inorganic ion)
- Conjugated protein: globular protein with a prosthetic group
Comparison between Haemoglobin and Collagen
Feature Haemoglobin Collagen
Type of protein stucture globular fibrous
No.of polypeptides 4 3
3D structure folded into ball twisted into long fibres
Helical structure right-handed alpha left-hand
Solubility in water soluble insoluble
Types of amino acids Most of the 20 Just 3 amino acids
Prosthetic group haem none
Role transport of 02 provides strength in many areas of the body: cartilage, bone, elasticity of skin