1.4.2: Enzymes

Question 1

What is a biological catalyst

Answer 1

Catalyst produced by living tissue, speeds up rate of reaction and is not altered by reaction

Question 2

what is the term given to enzymes that ‘break down’

Answer 2

catabolic enzymes

Question 3

what is the term given to enzymes that ‘build up’

Answer 3

anabolic enzymes

Question 4

what are catabolic enzymes

Answer 4

enzymes that ‘break down’

Question 5

what are anabolic enzymes

Answer 5

enzymes that ‘build up’

Question 6

describe the structure of an enzymes and how it is specific

Answer 6

enzymes are complementary in shape to their substrates, the enzyme’s active site is specific to the substrate

Question 7

what are the locations of enzyme action

Answer 7

intracellular - found in the cell (lysosomes, organelles, cytoplasm)
extracellular - found in digestion system (alimentary canal)

Question 8

How do enzymes act as a catalyst

Answer 8

they lower the activation energy of a reaction

Question 9

what is the name given to a reaction that releases energy

Answer 9

exergonic reaction

Question 10

what is the name given to a reaction that requires energy

Answer 10

endergonic reaction

Question 11

what is an endergonic reaction

Answer 11

a reaction that requires energy

Question 12

what is an exergonic reaction

Answer 12

a reaction that releases energy

Question 13

describe the lock and key mechanism

Answer 13

active site of enzyme is complementary in shape to substrate, forming an enzyme-substrate complex. Once reaction is complete, products are made and enzymes remains unchanged

Question 14

Describe and explain the induced fit theory for an enzyme substrate complex

Answer 14

1 - enzyme’s active site is not initially completely complementary to substrate
2 - forces cause the enzyme to slightly altar (distort its shape) for substrate to fit similar to hand and glove
3 - enzyme substrate complex forms

Question 15

what is a limiting factor in an enzyme controlled reaction

Answer 15

the number of available enzyme active sites

Question 16

how can you calculate the rate of reaction when the dependent variable is time taken and what are the units

Answer 16

1 / time taken for reaction to occur (seconds)
x 1000
units = s^-1 x 10^-3

Question 17

how can you calculate the rate of reaction when the dependent variable is mass or volume and what are the units

Answer 17

volume or mass /time (seconds)
units = cm^3s^-1

Question 18

list 4 factors that affect enzyme action

Answer 18

temperature
pH
substrate concentration
enzyme concentration

Question 19

describe the graph of the rate of reaction against temperature of an enzyme controlled reaction

Answer 19

initially as temp increases, rate of reaction increases, maximum rate of reaction at optimum temperature for enzyme, as temp increases beyond optimum, rate of reatcion decreases

Question 20

why does the rate of reaction initially increase as temperature increases of an enzyme controlled reaction

Answer 20

because there is an increase in kinetic energy of enzymes and substrates and so more successful collisions -> more enzyme substrate complexes form -> more product formed per unit of time

Question 21

why does the rate of reaction decreases as temperature increases beyond the enzyme’s optimum temperature of an enzyme controlled reaction

Answer 21

because further increase in kinetic energy causes enzyme to vibrate which breaks hydrogen bonds between r groups in tertiary structure -> change in tertiary structure -> change in shape of active site and so enzyme is denatured -> active site is no longer complementary in shape to substrate -> fewer ESC form -> less product formed per unit of time

Question 22

describe a pH graph of rate of reaction in an enzyme controlled reaction

Answer 22

when pH is very low, enzymes are denatured (tertiary ionic bonds broken) so rate of reaction is very slow
as pH increases and reaches optimum pH of enzyme, rate of reaction is highest, as pH increases further beyond optimum, rate of reaction decreases, further increase of pH leads to enzymes denaturing (tertiary ionic bonds broken)

Question 23

how do you maintain the pH of a reaction

Answer 23

use a pH buffer

Question 24

How would you set up an enzyme control experiment

Answer 24

boil the enzyme then cool it

Question 25

describe and explain the graph of substrate concentration against rate of reaction of an enzyme controlled reaction

Answer 25

initially as substrate concentration increases, rate of reaction increases because here substrate concentration is the limiting factor
after a certain substrate concentration, further increase in substrate conc results in the rate of reaction to become constant because here enzyme concentration is the limiting factor

Question 26

describe and explain the graph of enzyme concentration against rate of reaction of an enzyme controlled reaction

Answer 26

initially as enzyme concentration increases, rate of reaction increases because here enzyme concentration is the limiting factor
after a certain enzyme concentration, further increase in enzyme conc results in the rate of reaction to become constant because here substrate concentration is the limiting factor

Question 27

what is an enzyme inhibitor

Answer 27

a molecule that can interfere/slow down enzyme activity

Question 28

how does a competitive enzyme inhibitor function and how does it affect enzyme action

Answer 28

inhibitor has a similar shape to the substrate and so is complementary in shape to the active site, inhibitor can bind to active site blocking substrate from doing so -> fewer enzyme substrate complexes are formed and so less product formed per unit of time

Question 29

can you achieve maximum rate of reaction if there is a competitive enzyme inhibitor and if so then how

Answer 29

yes it can be, by increasing substrate concentration and can out compete the inhibitor

Question 30

how does a non-competitive enzyme inhibitor function and how does it affect enzyme action

Answer 30

inhibitor has a different shape to substrate, binds to enzyme at a point other than the active site (known as the allosteric site). This changes the tertiary structure of enzyme -> changes active site -> enzyme denatures -> substrate no longer complementary in shape to active site -> fewer ESC formed and so less product formed per unit time

Question 31

can you achieve maximum rate of reaction if there is a non-competitive enzyme inhibitor and if so then how

Answer 31

no as the enzyme has denatured

Question 32

describe the process of end product enzyme inhibition and what a metabolic pathway is and when does this happen

Answer 32

the final product of a metabolic pathway (series of stages for a reaction) can inhibit one of the earlier enzyme in the pathway and so stop production of the product - this happens when there is excess product