Topic 1---A: Biological molecules- 7. Factors affecting enzyme activity Flashcards
1
Q
How do you measure enzyme activity?
A
- How fast the product is made
- How fast the substrate is broken down
2
Q
How fast the product is made (measure of enzyme activity)
A
- There are different molecules present at the end of a chemical reaction than there is at the beginning.
- By measuring the amount of end product present at different times during the experiment the reaction rate can be calculated.
3
Q
How fast the substrate is broken down (measure of enzyme activity)
A
- To produce the end products in a reaction, substrate molecules have to be used up.
- By measuring the amount of substrate molecules left at different times of the experiment the reaction rate can be calculated.
4
Q
Factos affecting enzyme activity?
A
- Temperature
- pH
- Substrate concentration
- Enzyme concentration
- Competitive inhibitors
- Non-competitive inhibitors
5
Q
Temperature
A
- Rate of an enzyme-controlled reaction increases when the temperature increases
- As there is more kinetic energy so molecules move faster
- Makes the substrate molecules more likely to collide with the enzymes active site.
6
Q
What happens if the temperature gets too high?
A
- The reaction stops
- As a rise in temperature makes makes the enzymes molecules to vibrate more
- And if the temperature goes above a cerrtain level the vibration breaks some of the bonds that hold the enzyme in shape
- So the active site changes shape and the enzyme and substrate no longer fit together
- Enzyme denatures so no lunger functions as a catalyst
7
Q
What do enzymes have that are different and what does it mean?
A
- Different enzymes can have different optimum temperatures
- This means they can denature at different times
8
Q
pH
A
- All enzymes have an optimum pH value
- Above and below the optimum pH, the H + AND OH- ions found in acids and alkalis can disrupt the ionic and hydrogen bonds that hold the enzymes tertiary structure in place.
- The enzyme becomes denatured and the active site changes shape.
9
Q
Substrate concentration
A
- Increasing the concentration of substrate increases the rate of reaction.
- There are more substrates meaning a collision between substrate and enzyme is more likely so more active sites will be occupied ( greater chance of enzyme-substrates being formed)
- This is a steady increase.
- Only true up until a ‘saturation’ point
- After that, there are so many substrate molecules compared to the enzymes molecules as all their active sites are occupied.
- So there are no free enzymes to form an enzyme- substrate complex.
- Slows down
10
Q
Enzyme concentration
A
- Increasing the concentration of enzyme increases the rate of reaction.
- As if there are more enzymes it means it’s more likely a substrate molecule is to collide with one and form an enzyme- substrate complex.
- This is a steady increase as more active sites (on the enzyme) are available.
- But if there are more enzymes compared to substrate molecules it means that some active sites will be unoccupied so enzyme- substrate complexes won’t be formed
- Substrate reaction is a limiting factor so rate of reaction levels off.
11
Q
What can enzyme activity be prevented by?
A
Enzyme inhibitors
12
Q
What are enzyme inhibitors?
A
- They are molecules that bind to the enzyme they inhibit.
- They slow down or stop enzyme-catalysed reactions.
- Enzyme inhibitors can either be competitive or non-competitive.
13
Q
Competitive inhibitor
A
- They have a similar shape to that of substrate molecules.
- They compete with the substrate to bind to the active site
- They block the active site so no substrate molecules can fit in (no enzyme- substrate complexes can be formed)
14
Q
What happens if there is a high concentration of the competitive inhibitor?
A
- They will take up nearly all the active sites so hardly any of the substrates will get to the enzyme.
- So effect on inhibition is greater.
15
Q
What happens if there is a high concentration of substrates compared to competitive inhibitors?
A
- The substrates chances of getting to the active site before the inhibitor increases so the more substrate molecules the rate of reaction will increase.
- So effect of inhibition is reduced
16
Q
Non-competitive inhibitors
A
- They bind to the enzyme away from it’s active site.
- This causes the active site of the enzyme to change shape by breaking some hydrogen bonds and forming incorrect ones in the tertiary structure.
- Substrate molecules can no longer bind to the active site (no enzyme- substrate complexes can be formed)
17
Q
Why won’t increasing the concentration of substrates not have an effect on the non-competitive inhibitor?
A
- As the non-competitive inhibitors bind to the enzyme and they don’t compete with the substrate molecules to bind to the active sites because there are different shapes.
- So enzyme activity will still be inhibited.
18
Q
What happens to an enzymes shape and function when it is denatured?
A
- The bonds that hold the enzyme in place are broken which alters the shape of the active site meaning it is no longer a complementary shape to the substrate.
- So the enzyme can’t catalyse a reaction.
19
Q
What does saturation point mean?
A
It’s the point by which all active sites are occupied by the substrate molecules.
