Proteins Flashcards
Proteins
> a diverse group of large and complex polymer molecules, made up of long chains of amino acids
Biological roles: (4)
> structural - (body tissues)
catalytic - (enzymes)
signalling - (hormones, receptors)
immunological - (antibodies)
R groups
> represents a side chin from the central ‘alpha’ carbon atom
only difference between each amino acid
(can be a simple hydrogen atom or a complex ring structure)
Protein synthesis:
> amino acids form proteins or polypeptide chains in condensation reactions (peptide bonds form between amino acids)
Polypeptides:
> when more amino acids are added to a dipeptide, a polypeptide chain forms
a protein consists of one or more polypeptide chain folded into a highly specific 3D shape
Primary structure:
> the order (sequence) of amino acids in a polypeptide chain
(polymer)
Secondary structure:
> the sequence of amino acids causes parts of a protein to bend into a shape
a-helix or b-pleated sheet
hydrogen bonds form between C=O of one amino acid, and H (of amine group) of another amino acid
Tertiary structure:
> the secondary structure is bent and folded into a precise 3D shape held together by:
hydrophilic and phobic interactions
hydrogen bonds
ionic bonds between R groups
disulphide bonds (strong covalent bonds - only between R groups containing sulphur)
Quaternary structure:
> a protein made up of more than one polypeptide chain
Globular proteins:
> protein is folded into its tertiary structure
hydrophobic R groups are on the inside
hydrophilic R groups are on the outside
Globular proteins: Properties
> compact
usually spherical
soluble in water
functions - chemical reactions, immunity, muscle contractions
Conjugated proteins:
> globular proteins that contain a non-protein ‘prosthetic goup’
Prosthetic groups:
> co-factors (used when necessary for the function of the protein)
lipids = lipoproteins
carbohydrates = glycoproteins
metal ions, vitamin molecules, etc
Fibrous proteins:
> formed from long insoluble molecules
repetitive amino acid sequence in primary structure
organised, strong structure
