Proteins are all made from chains of amino acids

Key words about proteins polymer monomer amino acidcondensation amino group hydrolysis carboxyl groupprimary R groupsecondary peptide bondtertiary polypeptidequaternary Biuret testessential

Building a protein from amino acids

Collagen – a fibrous protein

Haemoglobin – a globular protein with a quaternary structure

Primary, secondary, tertiary or quaternary structure? sequence of amino acids in a protein haemoglobin has 4 polypeptide chains polypeptide forms a alpha helix held by many weak hydrogen bonds held by a variety of bonds e.g.disulphide, hydrogen and ionic held by peptide bonds

Haemoglobin and collagen – two proteins elements C, H, O and N monomer = amino acids joined by strong peptide bonds polypeptide chain made at ribosomes by condensation reactions have a primary structure determined by DNA in the chromosomes have a secondary structure held by many weak hydrogen bonds

collagen a regular sequence of amino acids with glycine every 3 rd one 3 polypeptide chains held by hydrogen bonds = fibrous protein insoluble has great tensile strength found in connective tissue e.g. tendons, ligaments, under skin

haemoglobin an irregular sequence of amino acids in the primary structure 4 polypeptides folded into a precise 3D shape + 4 haem groups = globular protein tertiary and quaternary structure held by ionic, disulphide, hydrogen and hydrophobic bonds soluble with hydrophilic parts outside molecule each molecule carries 4 molecules of oxygen attached to haem group (contains iron) found inside red blood cells mutation in DNA changes one amino acid and produces sickle cell haemoglobin – doesn’t carry oxygen as efficiently because shape of molecule has changed but gives resistance to malaria

Proteins :- if these are the answers, what are the questions? 1)peptide 2)amino acid 3)carboxyl 4)nitrogen 5)polypeptide 6)twenty 7)ionic, hydrogen, disulphide, hydrophobic 8)hydrogen 9)haemoglobin 10)collagen

Haemoglobin and collagen – two proteins with different functions Read in textbooks, research other sources and use the phrases to explain why these molecules are both proteins but have different functions. 20 marks Remember to record your information sources.