Proteins Flashcards
What are proteins?
Polymers made of monomers called amino acids
How many amino acids are in proteins?
20 - each determined by their different R groups
What are 4 elements bonded to a carbon atom in the structure of Amino acids?
Carboxylic group
Hydrogen atom
Amino group
R group
What is an R group?
A variety of different chemical groups. Each AA has a different R group. These 20 naturally occurring AA differ only in their R group
How are Amino acids joined?
Condensation
Water is made by combining an OH from the carbonyl group of one AA, with a H from the amino group of another AA. They link to make a peptide bond between the carbon atom of one AA, and Nitrogen of the other AA
How can a peptide bond of a dipeptide be broken down?
Hydrolysis
What is a dipeptide?
Contains 2 amino acids
What is a polypeptide?
Contains 3 or more amino acids
Describe the Primary structure
Polymer
The order (sequence) and number of amino acids in a proteins polypeptide chain
Contains initial sequence of amino acids and will therefore determine the proteins function in the end
Describe the Secondary structure
The shape the chain of AA makes - either alpha helix or beta pleated sheets
The H in -NH has a slight + charge whilst O in -C=O has a slightly - charge. As a result weak H bonds can form leading to alphas helices of beta pleated sheets
Describe the Tertiary structure
The 3D shape of the protein and is formed from further twisting and folding. A number of different bonds maintain the structure:
- Disulphide bridges - interactions between sulfur in R group of AA cysteine these are strong and not easily broken
- Ionic bonds - forms between carboxylate and amino groups not involved in the peptide bond - easily broken by pH and are weaker that disulphide bridges
- H bonds - numberous and easily broken
What is the test for proteins?
Biuret test
Describe the Quaternary structure
A protein made up of more than one polypeptide chain
