factors effecting enzyme activity 4.2

Question 1

How does changing temperature effect the activity of enzymes

Answer 1

increasing the temperature of a reaction environment increases the kinetic energy of the particles.
As temperature increases, the particles move faster and collide more frequently.
In an enzyme-controlled reaction an increase in temperature will result in more frequent successful collisions between substrate and enzyme resulting in an increased rate of reaction

Question 2

what is the temperature coefficient (Q10) of a reaction

Answer 2

is a measure of how much the rate of a reaction increases with a 10°C rise in temperature. For enzyme-controlled reactions this is usually taken as 2, which mean that the rate of reaction doubles with a 10°C temperature increase

Question 3

what happens to the structure of proteins at higher temperatures

Answer 3

At higher temperature the bonds holding the protein together vibrate more,
As the temperature increases the vibrations increase until the bonds strain and then break.
The breaking of these bonds results in a change in the precise tertiary structure of the protein.
The enzyme has changed shape and is said to have been denatured

Question 4

what happens to the active site of an enzyme that is denatured

Answer 4

when an enzyme is denatured the active site changes shape and is no longer complementary to the substrate. The substrate no longer fits the active site and the enzyme is no longer function as a catalyst

Question 5

what is meant by the optimum temperature

Answer 5

the optimum temperature is the temperature at which the enzyme has the highest rate of activity.

Question 6

what is the most common optimum temperature for enzymes working in the human body

Answer 6

Many enzymes in the human body has optimum temperatures of around 40°C

Question 7

what are some enzymes with more extreme optimum temperatures

Answer 7

thermophilic bacteria (found in hot springs) have enzymes with optimum temperatures of 70°C. Psychrophilic organisms (live in areas of cold such as artic regions) have enzymes with optimum temperatues below 5°C

Question 8

how is the rate of reaction effected by the denaturing of enzymes

Answer 8

once the enzymes have denatured above the optimum temperature, the decrease in rate of reaction is rapid.

There only needs to be a slight change in shape of an active site for it to no longer be complementary to its substrate this happens to all of the enzymes molecules at about the same temperature so the loss of activity is relatively abrupt

Question 9

does the temperature coefficient relate to denatured enzymes

Answer 9

At this point in an enzyme-controlled reaction the temperature coefficient, Q10 does not apply any more as the enzymes denatured

Question 10

whats the effect on rate of reaction if the temperature drops below the optimum temperature

Answer 10

The decrease in the rate of reaction below the optimum temperature is less rapid. This is because the enzymes have not denatured, they are just less active

Question 11

how do the enzymes evolved for cold temperature extremes differ structural from ‘normal’ enzymes

Answer 11

enzymes adapted the cold tend to have more flexible structures, particularly at the active site, making them less stable than enzymes that work at higher temperatures.
smaller temperatures changes will denature them

Question 12

how do the enzymes evolved for hot temperature extremes differ structural from ‘normal’ enzymes

Answer 12

The enzymes present in these organisms are more stable than other enzymes due to the increased number of bonds, particularly hydrogen bonds and sulfur bridges, in their tertiary structure.
The shape of these enzymes and their active site are more resistant to change as the temperature rises

Question 13

what type of bonds hold proteins in their tertiary structure

Answer 13

hydrogen bonds and ionic bonds between amino acid R-group hold proteins in their precise 3D shape

Question 14

what does a change of Ph actually mean

Answer 14

A change in Ph refers to a change in hydrogen ion concentration.

More hydrogen ions are present in low PH (acid) environments and fewer hydrogen ions are present in high PH (alkaline) environments

Question 15

what would happen to the active site If there is a change in PH from the optimum

Answer 15

changes from the optimum the structure of the enzyme, and therefore the active site, is altered.

Question 16

what is renaturisation

Answer 16

if the PH returns to the optimum then the protein will resume its normal shape and catalyse the reaction again

Question 17

Are changes to enzymes from PH always reversible

Answer 17

• drastic changes in pH can irreversible alter structure
  ^activate site no longer complementary to substrates
• ^The enzyme is now said to be denatured.

Question 18

how does a change in PH change the structure of the enzymes

Answer 18

Hydrogen ions interact with polar and charge R-groups. Changing the concentration of hydrogen ions therefore changes the degree of this interaction.
The interaction of R-group with hydrogen ions also affects the interaction of R-groups with eachother

Question 19

what does a change in hydrogen ion concentration do to bonds within proteins

Answer 19

The more hydrogen ions present (low Ph), the less the R-groups are able to interact with each other.
This leads to bonds breaking and the shape of the enzyme changing.
The reverse is true when fewer hydrogen ions (high PH) are present

Question 20

what are some optimum PHs for some enzymes within the human body

Answer 20

Question 21

what would occur to the rate of reaction if the concentration of substrate is increased

Answer 21

The increased number of substrate particles leads to a higher collision rate with the active sites of enzymes and the formation of more enzyme-substrate complexes.
The rate of reaction therefore increases

The same can be said if the concentration of enzymes is increased

Question 22

what is meant by Vmax

Answer 22

the rate of reaction increases up to its maximum (Vmax).
At this point all of the active sites are occupied by substrate particles and no more enzyme-substrate complexes can be formed until products are released from active site

Question 23

what are the only ways to increase the rate of reaction above Vmax

Answer 23

The only way to increase the rate of reaction would be to add more enzymes or increase the temperature