proteins Flashcards
(34 cards)
what are the four levels of protein structure?
primary, secondary, tertiary and quaternary
what does primary structure play a role in?
determines its secondary, tertiary and quaternary structures
describe primary structure
Linear sequence of amino acids in the polypeptide chain.
determines the proteins higher level structures.
described by the sequence of amino acids and peptide bonds.
describe secondary protein structure
is the conformation of amino acids in localised regions of a protein. two types alpha- helix and beta-pleated sheet. both due to hydrogen bonding.
alpha helix
common secondary structure.
formed when polypeptide chain twists into a helical conformation.
rod like structure
example of alpha helix
myoglobin
beta pleated sheet
polypeptide chain almost fully extended.
2 or more polypeptide chain segments line up side by side each referred to as a beta strand. folded over a lot.
what is tertiary protein structure?
overall folding pattern or three dimensional conformation of a polypeptide chain.
what interactions stabilise tertiary structures?
hydrophobic interactions
ionic interactions
hydrogen bonds
covalent bond
describe hydrophobic interactions
hydrophobic R groups brought into close proximity. Buried in the protein interior away from water
describe ionic interactions
opposite charged amino acid side chains can form ionic bonds
describe hydrogen bonds between
between polar side chains or with water
describe covalent bonds between
disulfide linkages between cysteine residues
what is quaternary protein structure
is the overall protein structure that results from the aggregation of two or more polypeptide chains
in quaternary protein structure do subunits have to be identical
no, they may be identical or different
what is an example of quaternary protein structure?
hemoglobin
describe globular proteins
Round/ spherical
functional role
soluble in H2O
contain several types of secondary structure
eg enzymes, antibodies
describe fibrous proteins
long
narrow
structural roles
eg collagen keratin
what is osteogenesis imperfecta caused by ?
replacement of glycine by tryptophan which gives defective collagen molecules.
it is abnormal bone formation
sickle cell anemia
inherited blood disorder, results from a single amino acid substitution in the beta- globin chains in the protein hemoglobin.
phenylketonuria PKU
caused by a deficiency in the enzyme phenylalanine hydroxy
Amino acids not stored
amino acids exceeds bodys needs
concentration of phenylalanine in the body can build up to toxic levels
what is the 3D structure of a protein determined by ?
its amino acid sequence
what are the most important forces stabilising protein structure
are non-covalent interactions
what does the function of the protein depend on?
its structure
