enzymes - the effect of temperature on enzyme activity Flashcards
define Q10
temperature coefficient
–> calculated by dividing the rate of reaction at (T + 10) degrees celsius by the rate of reaction at T degrees celsius
what do all molecules have ?
kinetic energy
what do molecules do to one another ?
collide into each other
what happens if a substance is heated ? (3 marks)
–> 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
what happens if the reactant mixture containing enzyme and substrate molecules is heated ?
–> 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
the enzyme’s optimum temperature
the rate of reaction at its maximum
what does increasing the temperature do to molecules ?
make them vibrate
what may heat do to weak bonds ?
break them
give example of bonds that may break and what’s the importance of them in an enzyme ? (2 marks )
- hydrogen and ionic bonds
–> they hold the tertiary structure of the enzyme’s active site
what happens of the active site’s shape begins to change ?
–> the substrate molecules won’t fit so well
–> the rate of reaction begins to decrease
what happens when more heat is applied ?
the shape of the enzyme’s active site completely and irreversibly changes
–> so no longer complementary to the shape of the substrate molecules
what would the enzyme be referred as in the description above ?
denatured
what does heat NOT break + therefore ?
peptide bonds between amino acids
–> therefore the enzyme’s primary structure is not altered
what is optimum temperature ?
this is the temperature at which the enzyme works best
where do some enzymes work best at ?
cool temperatures
what is an example of organisms that are adapted to living in cold conditions ?
psychrophillic bacteria
–> live in very cold conditions
–> enzymes can work at really low temperatures
what is an example of organisms that are adapted to living in high temperatures ?
thermophillic bacteria
–> live at very high temperatures
what are the enzymes in hot conditions and how ?
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
what is the formula for rate of reaction ?
1 / time taken to reach end point
what is the units for rate of reaction ?
s-1
draw and label the rate of reaction graph with temperature
find in textbook :)
describe what is happening in the graph above
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
what does this graph have an optimum temperature of ?
50-60’c
what is the Q10 approxiamtely for chemical reactions ?
2 - which means that for every 10 degrees celsius rise in temperature the rate of reaction is doubled
between the temperatures 0-40 in metabolic reactions catalysed by enzymes the reactions are … and why ?
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
what happens to enzymes at temperature above their optimum temperatures ?
- 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
what enzyme could on use to investigate the effect of temperature change ?
phosphatase enzyme
what does the enzyme above do/function ?
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
when conducting the effect of temperature on phosphate enzyme one must wear ?
eye protection
what chemical is used in this investigation ?
a chemical substrate phenolpthalein phosphate (PPP)
what does phosphate enzyme break down and leads too.. ?
the chemical
releasing phenolphthalein
what is sodium carbonate and what is it added to ?
alkaline + excess
what does the phenolpthalein produce ?
a deep-pink colour
what is the intensity of the colour proportional to ?
the concentration of free phenolpthalein
how can the intensity be measured ?
using a colorimeter with a green filter
if each reaction tube has been given the same length of time …
the intensity of the colour gives an indication of the rate of reaction
the darker the pink ….
the more molecules of PPP were hydrolysed by the enzyme in the set period of time
explain why the rate of enzyme controlled reactio is lower at 10 degrees celisus than it is at 30 degrees celisus
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
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
explain why using living tissue, such as bean sprouts , as a source of enzyme may lead to difficulties in controlling enzyme concentration
explain the difference between IV and DV
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
explain why , in an investigation about enzyme activity the enzyme solution is always added last
