Protein Structure Flashcards
What is definition of proteins?
Fundamental functional molecules of cell
What do proteins provide?
Carrier functions Metabolic functions Form parts of cellular machinery Make up structural scaffold Sensing molecules
Describe the structure of amino acid?
Tetrahedral arrangement of atoms with alpha carbon at its centre
Carboxyl + amine group attached to central carbon
Variable side chain= R group
Hydrogen
What happens to amino acid at low pH?
NH2 group accepts H+ to become NH3+
H+ AA acts as base
What happens to amino acid at high pH?
The COOH group loses a proton to form COO-
OH- behaves as acid with loss of H+
What are 2 isomers of amino acid called?
How are they different?
L amino acid => found in naturally occurring proteins of living organism
D amino acid => found in cell walls of some bacteria
When viewed along axis of hydrogen C-alpha bond, L would read CORN clockwise, D would read CORN in anti-clockwise direction
What is a residue?
Each repeating unit of a polypeptide chain
Describe the structure of beta sheets ( secondary structure)?
H bonds are formed between beta sheets to stabilise sheet
2 different arrangements where sheet is parallel or antiparallel=> they are formed H bonding between adjacent beta strands connected by loops either in antiparallel or parallel arrangement
Describe the structure of alpha helix?
Right handed helix
Stabilised by H bonds between 2 amino acids, 4 residues apart
Describe the tertiary structure?
Formed from folding of secondary structure into more densely packed generally globular structure
Give an example of proteins that require cofactors?
Haem of haemoglobin
NAD
FAD
Zn2+ , Mg2+ or Other ions
Note that organic cofactors= coenzymes