proteins and enzymes

Question 1

how are proteins made

Answer 1

amino acid monomers joining in a condensation reaction

Question 2

draw the general structure of an amino acid

Answer 2

see page 8 in revision guide it better match

Question 3

what group is H2N

Answer 3

AMINE GOUP

Question 4

what group is COOH

Answer 4

Carboxyl group

Question 5

what is the variable group

Answer 5

R group has 20 versions

Question 6

what bond forms when two amino acids bond in a condensation reaction?

Answer 6

a peptide bond

Question 7

what are dipeptides

Answer 7

two amino acids bonded in a condensation reaction

Question 8

what is a polypeptide

Answer 8

when more than two amino acids bond in a condensation reaction

Question 9

describe the primary structure of the protein

Answer 9

.the sequence of amino acids in a polypeptide chain
. the sequence is determined by DNA
.it determines the ultimate shape and function

Question 10

describe the secondary structure of the protein

Answer 10

.bonds between amino acids cause hydrogen bonds to form
.alpha coiled helix or b pleated sheets

Question 11

describe the tertiary structure

Answer 11

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

Question 12

describe the quaternary structure

Answer 12

several polypeptide chains held together by bonds

Question 13

describe the test for proteins

Answer 13

. add biuret
. positive result : purple . negative, blue

Question 14

what does an enzyme do

Answer 14

.a biological protein catalyst that speeds up reactions by lowering activation energy

Question 15

describe enzyme structure

Answer 15

a protein
specific 3D shape
active site
tertiary structure

Question 16

explain lock and key theory

Answer 16

that the enzymes active site is very specific and only binds to one substrate, an old theory

Question 17

explain induced fit model

Answer 17

enzyme and substrate collide making active site to change shape slightly, this is because the active site isn’t exactly complementary to the substrate

Question 18

how is the primary structure( sequence of amino acids) determined?

Answer 18

. by a gene
. in the case of a mutation, tertiary structure may be different

Question 19

what factors affect enzyme activity?

Answer 19

.pH
.temperature
.enzyme concentration
.substrate concentration
.competitive inhibition
. non-competitive inhibition

Question 20

what causes a pH change?

Answer 20

an increase or decrease in Hydrogen ions

Question 21

how does pH effect the rate of enzyme action?

Answer 21

.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

Question 22

what causes a temperature change?

Answer 22

an increase in kinetic energy

Question 23

what usually happens when temperature exceeds 60 or is beyond optimum (37)

Answer 23

.bonds holding amino acids will break
.active site shape will change
.no more enzyme-substrate complexes
.denture

Question 24

how does enzyme concentration affect enzyme action?

Answer 24

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

Question 25

how can enzyme activity be inhibited?

Answer 25

. competitive inhibition
. non-competitive inhibition

Question 26

describe competitive inhibition?

Answer 26

.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

Question 27

describe non-competitive inhibition

Answer 27

. 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

Question 27

state control variables in an enzyme activity experiment

Answer 27

.pH
.temperature
.enzyme concentration
.substrate concentration

Question 27

how to use a tangent to calculate the initial rate of reaction

Answer 27

.draw a tangent to the curve at time=0
.find gradient which is change in y over change in x