What are the two main forms of protein
1) precisely shaped 3D globular proteins which are functional
2) long fibrous, cross linked structural proteins
What do precisely shaped 3D globular proteins do
They ‘do things’ regulate processes - enzymes, immunity, muscle contraction
I.e insulin binds with specific receptor on cell surface membranes
What do precisely shaped 3D globular proteins have
They have a specifically shaped region for recognition purposes e.g. enzymes, antibodies and antigens, hormones and haemaglobin
What are long fibrous cross linked structural proteins
They are long strong insoluble molecules not folded into precise 3D shapes I.e. collagen in skin, keratin in hair and nails, elastin in the walls of blood vessels
What are proteins
They are polymers made from monomers called amino acids that have been polymerised to n condensation reactions
What do all amino acids contain
Carbon, hydrogen, oxygen and nitrogen (CHON)
What does one amino acids, cysteine also contain
Sulfur (S) in its variable R group
General formula of amino acid is
NH2CHRCOOH
What happens in an acid solution
A H+ is accepted by the -NH2 group to reduce acidity
What happens in an alkaline solution
The -COOH groups releases H+ so reducing alkalinity
What is a peptide bond?
All 4 atoms - carbon, hydrogen, nitrogen and oxygen
Why are amino acids important (buffers)
They are important buffers; they keep the blood pH of etching certain narrow limits
amphoteric def
Can be acid or alkali
What gives the primary protein structure
The sequence of amino acids in a polypeptide chain
Most common forms of secondary protein structure
Alpha helix
Beta pleated sheet
How is the secondary structure maintained?
By R groups on the amino acid residues
What does tertiary structure produce
The precise 3D shape which is important in cellular recognition, enzymes etc
What is tertiary structure maintained by
H bonds and ionic bonds between R groups of various amino acids
Hydrophilic side chains s orientating themselves to the inside whilst hydrophobic groups orient themselves to the outside
Disulphide bridges are very strong covalent bonds formed between sulphur atoms in the R groups orient themselves of cysteines
Quaternary structure
Proteins made of more than 1 polypeptide chain
An example of quaternary structure
Haemoglobin - made of 4 polypeptide chains
Why is insulin a different quaternary structure
Because unlike other hormones it is made of 2 DIFFERENT polypeptide chains
How are proteins denatured by heat
Extreme temp denatures proteins by energy breaking the H bonds that maintain specific shape, and the precise 3D shape of the protein changes
Example of temperature denaturing proteins and changing the precise 3D shape
Enzyme active site is no longer the complementary shape to its target molecule
How are proteins denatured by heat
If higher (H+) than usual H+ joins to COO to produce COOH
If lower H+ is released from NH3 to produce NH2
This breaks the ionic bonds changing the precise 3D shapes, denaturing the protein
