Proteins Flashcards
What are proteins?
Organic molecules with carbon, hydrogen, oxygen and nitrogen. Made of amino acid monomers in chains called polypeptides, the shape of proteins are decided by sequence of amino acids.
How many amino acids are used to make proteins?
About 20
Structure of amino acid:
Diagram on notes:
Amino group NH2
Carboxyl group COOH
Hydrogen atom
R group
Why can an amino acid be a Zwitterion
If amine group gains H to become + and carboxyl group loses a H to become -
How do peptide bonds form?
In a condensation reaction between the amine group of 1 AA and carboxyl group of another. Water is eliminated, creating a dipeptide
Diagram on notes
What is primary structure of proteins?
Sequence of amino acids in polypeptide chains held together by peptide bonds
What is secondary structure of proteins?
Where polypeptide chains spiral to form alpha helices and fold to form beta pleated sheets due to weak hydrogen bonds forming
What is tertiary structure of proteins?
Where alpha helices and beta pleated sheets fold around each other to form a 3D structure held by ionic bonds disulphide bonds, hydrogen bonds and hydrophobic interactions. E.g. lysozyme
What is quaternary structure of proteins
2 or more polypeptide chains in tertiary structure bonded to form 1 large protein structure e.g. haemoglobin with 4 chains, at centre of each is haem group containing iron
What are globular proteins:
Shape: spherical
Strength: not strong
Solubility: soluble in water
Function: biochemical e.g. haemoglobin transports oxygen in blood, 4 chains each with haem group
What are fibrous proteins?
Shape: long fibres/sheets
Strength: very strong
Solubility: insoluble in water
Function: structural e.g. collagen underneath skin, tendons, ligaments, keratin (hair and nails)
