enzymes - the effect of temperature on enzyme activity

Question 1

define Q10

Answer 1

temperature coefficient
–> calculated by dividing the rate of reaction at (T + 10) degrees celsius by the rate of reaction at T degrees celsius

Question 2

what do all molecules have ?

Answer 2

kinetic energy

Question 3

what do molecules do to one another ?

Answer 3

collide into each other

Question 4

what happens if a substance is heated ? (3 marks)

Answer 4

–> the extra energy in the form of heat causes the molecules to move faster
–> this increases the rate of collisions between molecules
–> it also increases the force with which they collide , as they’re moving faster

Question 5

what happens if the reactant mixture containing enzyme and substrate molecules is heated ?

Answer 5

–> both types of molecule will gain kinetic energy and move faster
–> this will increase the rate of successful collisions
–> therefore the rate of formation of ES complexes increases, and the rate of reaction increases, increasing the number of EP complexes per second up to a point

Question 6

the enzyme’s optimum temperature

Answer 6

the rate of reaction at its maximum

Question 7

what does increasing the temperature do to molecules ?

Answer 7

make them vibrate

Question 8

what may heat do to weak bonds ?

Answer 8

break them

Question 9

give example of bonds that may break and what’s the importance of them in an enzyme ? (2 marks )

Answer 9

• hydrogen and ionic bonds
  –> they hold the tertiary structure of the enzyme’s active site

Question 10

what happens of the active site’s shape begins to change ?

Answer 10

–> the substrate molecules won’t fit so well
–> the rate of reaction begins to decrease

Question 11

what happens when more heat is applied ?

Answer 11

the shape of the enzyme’s active site completely and irreversibly changes
–> so no longer complementary to the shape of the substrate molecules

Question 12

what would the enzyme be referred as in the description above ?

Answer 12

denatured

Question 13

what does heat NOT break + therefore ?

Answer 13

peptide bonds between amino acids
–> therefore the enzyme’s primary structure is not altered

Question 14

what is optimum temperature ?

Answer 14

this is the temperature at which the enzyme works best

Question 15

where do some enzymes work best at ?

Answer 15

cool temperatures

Question 16

what is an example of organisms that are adapted to living in cold conditions ?

Answer 16

psychrophillic bacteria
–> live in very cold conditions
–> enzymes can work at really low temperatures

Question 17

what is an example of organisms that are adapted to living in high temperatures ?

Answer 17

thermophillic bacteria
–> live at very high temperatures

Question 18

what are the enzymes in hot conditions and how ?

Answer 18

heat stable
–> they have more disulfide bonds that do not break with heat
- - > they keep the shape of the protein molecules stable
–> their enzymes will have high optimum temperatures

Question 19

what is the formula for rate of reaction ?

Answer 19

1 / time taken to reach end point

Question 20

what is the units for rate of reaction ?

Answer 20

s-1

Question 21

draw and label the rate of reaction graph with temperature

Answer 21

find in textbook :)

Question 22

describe what is happening in the graph above

Answer 22

A- between A and B increasing temperature increases the rate of reaction due to increased kinetic energy
B - increasing temperature beyond the optimum (B) temperature reduces the rate of reaction due to the breaking of bonds holding the enzyme’s tertiary structure in place
C - there is no reaction because the enzyme is denatured

Question 23

what does this graph have an optimum temperature of ?

Answer 23

50-60’c

Question 24

what is the Q10 approxiamtely for chemical reactions ?

Answer 24

2 - which means that for every 10 degrees celsius rise in temperature the rate of reaction is doubled

Question 25

between the temperatures 0-40 in metabolic reactions catalysed by enzymes the reactions are … and why ?

Answer 25

doubled for every 10 degrees celisus rise in temperature
–> this is because the increases in temperature provides more kinetic energy, so enzyme and substrate molecules move faster and collide more often

Question 26

what happens to enzymes at temperature above their optimum temperatures ?

Answer 26

• the value of the temperature coeffiecent Q10 drops
  –> this is because the higher temperatures alter the structure of active sites of the enzyme molecules
• • > so they are no longer complementary to the shape of substrate molecules

Question 27

what enzyme could on use to investigate the effect of temperature change ?

Answer 27

phosphatase enzyme

Question 28

what does the enzyme above do/function ?

Answer 28

the enzyme breaks down organic phosphates in cells in order to maintain the pool of phosphate ions for use by cells to make chemicals such as ATP , ribulose biphosphate and NADP

Question 29

when conducting the effect of temperature on phosphate enzyme one must wear ?

Answer 29

eye protection

Question 30

what chemical is used in this investigation ?

Answer 30

a chemical substrate phenolpthalein phosphate (PPP)

Question 31

what does phosphate enzyme break down and leads too.. ?

Answer 31

the chemical
releasing phenolphthalein

Question 32

what is sodium carbonate and what is it added to ?

Answer 32

alkaline + excess

Question 33

what does the phenolpthalein produce ?

Answer 33

a deep-pink colour

Question 34

what is the intensity of the colour proportional to ?

Answer 34

the concentration of free phenolpthalein

Question 35

how can the intensity be measured ?

Answer 35

using a colorimeter with a green filter

Question 36

if each reaction tube has been given the same length of time …

Answer 36

the intensity of the colour gives an indication of the rate of reaction

Question 37

the darker the pink ….

Answer 37

the more molecules of PPP were hydrolysed by the enzyme in the set period of time

Question 38

explain why the rate of enzyme controlled reactio is lower at 10 degrees celisus than it is at 30 degrees celisus

Question 39

explain why an enzyme solution kept in the fridge for a week will catalyse a reaction at 40’c , whereas an enzyme solution that has been boiled doesn’t catalyse a reaction at 40 degrees celisus

Question 40

explain why the rate of an enzyme catalysed reaction does not keep on increasing as the temperature is increased above 40 degrees celisus or 50 degrees celisus

Question 41

explain why using living tissue, such as bean sprouts , as a source of enzyme may lead to difficulties in controlling enzyme concentration

Question 42

explain the difference between IV and DV

Question 43

explain why tubes of reactants and separate tubes of enzyme solutions are placed in water bath for 5- 10 mins before they are mixed and the reaction allowed to proceed

Question 44

explain why , in an investigation about enzyme activity the enzyme solution is always added last