enzymes🦴

Question 1

explain the induced fit model through the breakdown of a substrate

Answer 1

• substrate binds to active site
• active site shape changes shape to fit to substrate more closely
• more bonds form between active site and substrate
• forms ESC
• change in shape of active site weakens bonds in substrate
• activation energy reduced

Question 2

describe how an enzyme breaks down a substrate

Answer 2

• active site shape complementary to substrate
• active site binds to substrate
• induced fit
• forms esc
• puts strain on bonds in substrate
• forms enzyme product complex
• products leave active site

Question 3

how to increase validity of an experiment testing ph effect on enzyme

Answer 3

• equal volume in each tube

- add buffer

Question 4

how does repeating an experiment improve it

Answer 4

• improves reliability
• assess spread of results
• allows calculation of mean

Question 5

if a molecule is a competitive inhibitor what can you conclude about its structure

Answer 5

• similar shape/ tertiary structure to substrate

- complementary to active site of enzyme

Question 6

why are different enzymes involved at different stages of the breakdown of a large molecule

Answer 6

• enzymes are specific
• substrates are different shapes
• active site and substrate are complementary
• to form esc

Question 7

why would enzyme activity fall to zero at ph 7

Answer 7

• ph much higher than optimum
• change in charge of active site
• hydrogen/ionic bonds break
• 3D shape altered
• ESC does not form

Question 8

describe how to measure concentration of reducing sugar with colorimeter

Answer 8

• use known concentrations
• heat with benedicts solution
• use same volumes of solutions each time
• remove precipitate
• calibrate colorimeter using water
• less absorbance= more sugar
• plot absorbance against sugar concentration to get calibration curve
• use reading of unknown sugar solution and read off graph to find concentration

Question 9

what is extracellular enzyme

Answer 9

works outside cells

Question 10

how does substrate concentration affect enzyme rate

Answer 10

• rate increases
• more successful collisions with active site
• more ESC
• more product formation in given time
• levels off
• all active sites occupied
• enzyme working at max rate
• further increase in substrate concentration has no effect
• enzyme concentration becomes limiting factor

Question 11

why does ph need to be kept constant when testing temperature effect on enzyme

Answer 11

• so charges in active site do not change
• so hydrogen/ionic bonds are not affected
• so active site unaltered
• so enzyme does not denature
• so substrate fits active site
• so results are valid as only one variable changed

Question 12

why is there low enzyme activity below its optimum temperature

Answer 12

• low kinetic energy
• fewer collisions so less chance of ESC formation
• activation energy higher to reach

Question 13

in competitive inhibition how does increasing substrate help

Answer 13

-substrate more likely to collide with active site than inhibitor

Question 14

how would a more flexible structure allow enzyme to work at a low temperature

Answer 14

-easier for active site to change shape as part of induced fit

Question 15

if 2 organisms have the same enzyme with a different structure how might their dna differ

Answer 15

• different base sequence
• different proportion of bases
• different gene would code for polypeptide

Question 16

explain biological catalyst

Answer 16

speed up metabolic reactions

Question 17

describe how hydrogen bond forms

Answer 17

• between oxygen and hydrogen

- hydrogen slightly positive oxygen slightly negative charge

Question 18

how do chloride ions increase rate of reaction of amylase

Answer 18

• cofactors for amylase
• binds to active site
• esc forms more easily

Question 19

explain competitive inhibitor effect on reaction rate

Answer 19

• inhibitor competes with substrate for active site
• occupies active site reversibly
• fewer active sites available for substrate
• increasing substrate reduces chance of inhibitor getting in

Question 20

explain difference in enzyme rate at 37 degrees and 60 degrees

Answer 20

• at 60 more KE therefore more ESC
• initial rate is faster than 37
• however enzyme denatures and less product forms