factors effecting enzyme activity 4.2 Flashcards
How does changing temperature effect the activity of enzymes
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
what is the temperature coefficient (Q10) of a reaction
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
what happens to the structure of proteins at higher temperatures
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
what happens to the active site of an enzyme that is denatured
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
what is meant by the optimum temperature
the optimum temperature is the temperature at which the enzyme has the highest rate of activity.
what is the most common optimum temperature for enzymes working in the human body
Many enzymes in the human body has optimum temperatures of around 40°C
what are some enzymes with more extreme optimum temperatures
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
how is the rate of reaction effected by the denaturing of enzymes
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
does the temperature coefficient relate to denatured enzymes
At this point in an enzyme-controlled reaction the temperature coefficient, Q10 does not apply any more as the enzymes denatured
whats the effect on rate of reaction if the temperature drops below the optimum temperature
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
how do the enzymes evolved for cold temperature extremes differ structural from ‘normal’ enzymes
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
how do the enzymes evolved for hot temperature extremes differ structural from ‘normal’ enzymes
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
what type of bonds hold proteins in their tertiary structure
hydrogen bonds and ionic bonds between amino acid R-group hold proteins in their precise 3D shape
what does a change of Ph actually mean
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
what would happen to the active site If there is a change in PH from the optimum
changes from the optimum the structure of the enzyme, and therefore the active site, is altered.
what is renaturisation
if the PH returns to the optimum then the protein will resume its normal shape and catalyse the reaction again
Are changes to enzymes from PH always reversible
- drastic changes in pH can irreversible alter structure
^activate site no longer complementary to substrates - ^The enzyme is now said to be denatured.
how does a change in PH change the structure of the enzymes
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
what does a change in hydrogen ion concentration do to bonds within proteins
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
what are some optimum PHs for some enzymes within the human body
what would occur to the rate of reaction if the concentration of substrate is increased
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
what is meant by Vmax
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
what are the only ways to increase the rate of reaction above Vmax
The only way to increase the rate of reaction would be to add more enzymes or increase the temperature
