3.1.4 Proteins

Protein monomers- how many are there?

20 Amino acids

Protein monomer general structure

Peptide bond formed by

A condensation reaction between an amino acids amine group and another amino acid’s carboxyl group

Dipeptide

molecule made from two amino acids joined by a condensation

reaction

polypeptide

Molecules made from many amino acids joined together by

condensation reactions

T or F all polypeptides are proteins

F: protein is a polypeptide chain that has been folded up and modified to do a job

A polypeptide chain by itself is not functional

How many protein structure levels are there

4; primary, secondary, tertiary, quaternary

Define protein structure lvl 1

Order of amino acids in a polypeptide chain

Importance of protein structure lvl 1

If 1 amino acid is in different location, ionic/ disulphide/ hydrogen bonds form in different locations SO protein has different 3D shape SO enzymes have different shaped active sites and carrier proteins have different shaped binding sites

Define protein structure lvl 2

Where amino acid sequences either

a) bends into an alpha helix

b) folds into beta pleated sheets

What is protein structure lvl 2 held by and where are they located

Hydrogen bonds between the C=O group of one amino acid and the H group of another amino acid

Cause of change in amino acids sequence

Genetic mutation codes for different amino acid

Define protein structure lvl 3

Further folding of secondary structure into a 3D shape

What are the protein structure lvl 3 unique bonds other than secondary structure and explain each 3

Ionic bonds -

Formed between any carboxyl group and amine groups on R groups

Easily broken by pH changes

hydrogen bonds

Formed between O^б- and H^б- of different R groups

Many of these but easily broken

disulphide bonds (strong covalent bonds)

all are located in r group of different amino acids and disulphide bridges form between amino acids with sulphur atoms ONLY

Define protein structure lvl 4 and provide an example

A protein formed from more than 1 polypeptide chain like haemoglobin

Protein definition

A polymer made up of small repeating units of amino acids