proteins and enzymes Flashcards
how are proteins made
amino acid monomers joining in a condensation reaction
draw the general structure of an amino acid
see page 8 in revision guide it better match
what group is H2N
AMINE GOUP
what group is COOH
Carboxyl group
what is the variable group
R group has 20 versions
what bond forms when two amino acids bond in a condensation reaction?
a peptide bond
what are dipeptides
two amino acids bonded in a condensation reaction
what is a polypeptide
when more than two amino acids bond in a condensation reaction
describe the primary structure of the protein
.the sequence of amino acids in a polypeptide chain
. the sequence is determined by DNA
.it determines the ultimate shape and function
describe the secondary structure of the protein
.bonds between amino acids cause hydrogen bonds to form
.alpha coiled helix or b pleated sheets
describe the tertiary structure
the a helixes can be twisted even more to more complex and specific shape.
this 3d shape ii maintained by:
where the bonds occur depend on the primary structure
1) strong disulphide bridges
2) ionic bonds( can be broken by ph. fluctuations , weak)
3) easily broken hydrogen bonds
describe the quaternary structure
several polypeptide chains held together by bonds
describe the test for proteins
. add biuret
. positive result : purple . negative, blue
what does an enzyme do
.a biological protein catalyst that speeds up reactions by lowering activation energy
describe enzyme structure
a protein
specific 3D shape
active site
tertiary structure
explain lock and key theory
that the enzymes active site is very specific and only binds to one substrate, an old theory
explain induced fit model
enzyme and substrate collide making active site to change shape slightly, this is because the active site isn’t exactly complementary to the substrate
how is the primary structure( sequence of amino acids) determined?
. by a gene
. in the case of a mutation, tertiary structure may be different
what factors affect enzyme activity?
.pH
.temperature
.enzyme concentration
.substrate concentration
.competitive inhibition
. non-competitive inhibition
what causes a pH change?
an increase or decrease in Hydrogen ions
how does pH effect the rate of enzyme action?
.a change in pH alters charges (ionic and hydrogen bonds) holding the amino acids in the active site.
. changes tertiary unique structure of enzyme
. no longer complementary to substrate
. enzyme denature
what causes a temperature change?
an increase in kinetic energy
what usually happens when temperature exceeds 60 or is beyond optimum (37)
.bonds holding amino acids will break
.active site shape will change
.no more enzyme-substrate complexes
.denture
how does enzyme concentration affect enzyme action?
the more enzyme molecules there are, the more likely a substrate is to collide and form E-S complexes
. after some ti me the substrate becomes the limiting factor
how can enzyme activity be inhibited?
. competitive inhibition
. non-competitive inhibition
describe competitive inhibition?
.competitive inhibitors have a similar shape to substrate( it competes for the actives site)
. they bind to active site
. if there’s more inhibitor,less substrate will bond
. if there’s more substrate more e-s complexes will form
. the concentration of inhibitors does matter
describe non-competitive inhibition
. inhibitor binds to allosteric/ away/ opposite active site
. it changes the tertiary structure of enzyme, changing the complementary shape of the active site( does not compete)
.increasing concentration will not increase rate of enzyme action
. concentration does not matter
state control variables in an enzyme activity experiment
.pH
.temperature
.enzyme concentration
.substrate concentration
how to use a tangent to calculate the initial rate of reaction
.draw a tangent to the curve at time=0
.find gradient which is change in y over change in x
