Proteins (J) Flashcards
List the 5 elements that make up amino acids
Carbon Hydrogen Oxygen Nitrogen Sulphur
What are proteins made up of
Amino acids
Central carbon atom has 4 different chemical groups attached to it what are they?
A hydrogen atom
A basic amino group
An acidic carboxyl group
A variable “R” group ( or side chain)
How many different amino acids are there?
20 all have similar chemical structures but behave very differently because they have different side groups
Amino acids supplied through are diet are known as
Essential amino acids
ie leucine, lysine, valine, methionine
Amino acids made by the body are known as a process known as
Transamination which occurs in the liver
Proteins form which reaction
Condensation reaction which links amino acids together
What happens in the condensation reaction
A molecule of water is produced from a linkage between the -COOH of one amino acid and the NH2 of the next this is known as a Peptide Bond
The linked amino acid always has a free acid group at their end so other AA canbe added by the same reaction this is known as
Polypeptide
What is polypeptide
When many amino acids are joined together by peptide bonds
The breaking of a peptide bond using a water molecule is known as
Hydrolysis - reverse of condensation reactions
A reaction where 2 molecules joined by a condensation reaction are split apart again
Hydro- water required
Lysis- that a molecule is split apart
Primary Structure
Sequence of amino acids on the polypeptide chain, it determines the rest of the protein structure
Secondary Structure
Basic level of protein folding
Held together by hydrogen bonds between the carboxyl groups and the amino groups in the polypeptide backbone
a - helix. Alpha
B - sheet. Beta
a -helix. Alpha
The poly chain is wound round to form a helix held together by hydrogen bonds running parrallel with the long helical axis
A very stable and string structure due to is many hydrogen bonds
B - sheet. Beta
Zigzags back and forward forming a sheet.
Held together by hydrogen bonds.
Protein structure has 4 levels
Primary structure
Secondary structure
Tertiary structure
Quaternary structure
Tertiary structure
3 dimensional structure formed by the folding of a whole polypeptide chain. Held tog by bonds between the R groups of AA in the protein.
3 types of bonds involved
Hydrogen bonds
Ionic bonds
Sulphur bridges
Every protein has a tertiary structure responsible for its properties and functions
Quaternary structure
Describes the spatial organisation of the chains
Only exists if they is more than 1 polypeptide chain present in a complex protein.
Fibrous proteins
Made up of long molecules arranged to firm fibres (keratin). Several helices maybe wound each other to form very strong fibres
Collagen
Fibrous protein stronger than steel
Consists of 3 polypeptides chains coiled round each other in a triple helix
Humans are largely held tog by collagen found in are bones, cartilage, tendons and ligaments.
Summary
Primary protein structure - a sequence of a chain of amino acids
Secondary protein structure - occurs when the sequence of amino acids are linked by hydrogen bonds. alpha helix & beta sheets
Tertiary protein structure - occurs when certain attractions are present between alpha helices and beta sheets
Quaternary protein structure - is a protein consisting if more than 1 amino acid chain
A
