Biochemistry: Protein Structure and Function Flashcards
primary structure of protein
polypeptide chain of amino acid residues
secondary structure of protein
localised conformation of polypeptide backbone
tertiary structure of protein
3-D conformation of polypeptide including side chain
quaternary structure of protein
spatial arrangement of polypeptide chains in a protein with multiple subunits
at what angles can proteins rotate around
the alpha carbon and the amino acid group
the alpha carbon and the carboxyl group
3 types of secondary structures
- alpha-helices
- beta-sheets
- collagen triple helix
describe alpha-helices
- 1 chain, mostly R handed
- the carboxyl group binds with the amine group 4 residues away
why does proline break down alpha helices
causes a kink in the chain
describe beta-sheets
- can invole 1+ chains
- not folded, turns between strands
- C=O and N-H of neighbouring peptides form hydrogen bonds
what are beta-pleated sheets
repeated zig zag patterns
what is collagen a component of
bone and connective tissue
is collagen water in/soluble
insoluble
describe the structure of collagen
3 L-handed helical chains twist around each other to form a R-handed super helix - tropocollagen
what bonding occurs in tropocollagen
- inter-chain H bonds
- intra- and inter-molecular bonds
what happens as a result of weakened collagen
- bleeding gums - Scurvy
what is covalent crosslinking and what does it increase with
- covalent bonding of 2+ molecules, can alter properties
- age
2 types of tertiaty structures
- fibrous
- globular
describe the general structure of tertiary proteins
local regions with distinct secondary structures
describe fibrous proteins
- polypeptides arranged along 1 axis
- water insoluble and dilute salt solutions
- made of long fibres/large sheets
- mechanically strong
- structural roles
describe globular proteins
- folded into roughly spherical shape
- soluble in water and salt solutions
- polar chains on outside and non-polar on inside
- interact with aq environment bu H bonding and dipole-dipole interactions
- big helix and sheet sections
what forces stabilise tertiary structures
- covelant disulphide bonds
- electrostatic interaction (salt bridges)
- hydrophobic interactins
- H bonds
- complex with metal ions
how are disulphide bonds formed
via oxidation (often redox centres), 1 side reduced, other oxidised
what happens as a result of disulphide bonds
reversible changein shape and function
describe electrostatic interactions
- -ve attracts +ve
- charged side groups located on the outside of proteins and they react with water
- salt bridges
describe hydrophobic interactions
- strong organising influence
- hydrophobic side chains tend to cluster in the middle
what level of structure contain all the information needed for folding
primary
what specialised proteins aid folding of proteins
chaperons
when can proteins begin folding
- after translation
- before translation is finished
what can cause proteins to denature and why
- heat, increases vibrations within a protein
- pH, electrostatic interactions disrupted
- detergents, urea, guanidine, hydrochloride, disrupts hydrophobic interactions
- thiol and reducing agents, reduce and disrupt disulphide bonds
describe myoglobin’s structure and functions
- globular with a haem prosthetic group
- 1 haem group binds 1 oxygen molecules
- stored O2 in muscle
describe haemoglobins structure and function
- 2 alpha and 2 beta subunits, each containing a haem group - each binds 1 O2
- exhibits co-operativity
- transports O2 in blood
