Factors Affecting Enzyme Activity Flashcards
How can you measure the rate of reaction?
- How fast the product is made.
* How fast the substrate is broken down.
What is different between the beginning of a reaction and the end of a reaction?
There are different molecules present at the end of a chemical reaction than there are at the beginning.
How can you measure the rate of reaction by how fast the product is made?
By measuring the amount of end product preset at different times during the experiment.
How can you produce the end products in a chemical reaction?
Substrate molecules have to be used up.
How can you measure the rate of a reaction by how fast the substrate is broken down?
By measuring the amount of substrate molecules left at different times during the experiment.
What affects the rate of an enzyme-controlled reaction?
- Temperature
- pH
- Substrate concentration
- Enzyme concentration
How does temperature affect the rate of an enzyme-controlled reaction?
•When it is increased the rate of the reaction increases •When it is decreased so does the reaction rate.
Why does a higher temperature increase the rate of an enzyme-controlled reaction?
- The substrate molecules are more likely to collide with the enzyme’s active site.
- The collisions are more likely to result in an enzyme-substrate complex.
Why are the substrate molecules more likely to collide with enzymes at higher temperatures?
Because more heat means more kinetic energy, so molecules move faster.
Why are the enzyme-substrate collisions more likely to result in a complex at higher temperatures?
Because the energy of these collisions increases, so they collide with more force.
What happens when the temperature of a reaction gets too high?
The enzymes are denatured and the reaction stops.
How do high temperatures denature enzymes?
- The enzyme’s molecules vibrate more.
* The vibrations break some of the hydrogen bonds that hold the enzymes tertiary structure together.
What does enzymes being denatured cause the reaction to stop?
It can’t catalyse the reaction anymore.
Why can’t denatured enzymes catalyse their reaction anymore?
Because when the enzyme’s tertiary structure is changed, the active site changes shape and is no longer complementary to the substrate.
What does the effect of temperature on enzymes look like?
Image
Why are low temperatures not optimum for enzyme activity?
Because even tho the enzyme and substrate molecules are complementary, they do not have enough energy to collide.
What is the common optimum temperature for enzymes?
Those in humans at 37c
What does a graph showing the effect of temperature on the rate of an enzyme-controlled reaction look like?
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What do all enzymes have concerning pH
An optimum pH value.
What is the optimum pH value of humans?
7 (neutral)
What are some optimum pH value exceptions?
Pepsin works best at pH2 (acidic).
Why does pepsin work best at pH2?
Because its function takes place in the stomach.
What do enzyme optimum pH values always match?
Their function.
Why cant enzymes be in areas of pH values that are different to their optimum pH?
The enzyme becomes denatured, and the active site changes shape.
Why do enzymes become denatured at the wrong pH?
Because the H+ and OH- ions found in acids and alkalis can disrupt the ionic and hydrogen bonds that hold the enzyme’s tertiary structure in place.
What does a graph showing the effect of pH on the rate of an enzyme-controlled reaction look like?
image
How does substrate concentration affect enzyme activity?
- The higher the substrate concentration, the faster the reaction.
- The lower the substrate concentration, the slower the reaction.
Why does a higher substrate concentration increase the rate of reaction?
Because more substrate molecules means more enzyme-substrate collisions as more active sites will be occupied.
When does increasing substrate concentration stop increasing the rate of an enzyme-controlled reaction?
Until the saturation point.
What is the saturation point?
When all enzyme active sites are full, and adding more substrate does not affect the rate of reaction.
What does the affect of changing the substrate concentration on the rate of reaction look like?
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What does a graph showing the effect of substrate concentration on the rate of an enzyme-controlled reaction?
image
What does changing the enzyme concentration do the rate of reaction?
It increases it (sometimes up to the saturation point like substrate concentration).
How does adding more enzyme increase the rate of reaction?
The molecules are more likely to collide and form enzyme-substrate complexes.
What happens when you increase the enzyme concentration when the substrate concentration is limited?
There comes a point where all the substrate molecules are in an active site, so adding more enzymes has no further effect.
What does a graph showing the effect of enzyme concentration on the rate of an enzyme-controlled reaction look like?
image
How can enzyme activity be prevented?
By enzyme inhibitors.
What can inhibition be?
- Competitive
* Non-competitive
How do competitive inhibitors stop a reaction taking place?
They compete with the substrate molecules to bind to the enzymes active site and block it.
How can competitive inhibitors block the enzyme’s active site?
They have a similar shape to the substrate and thus are complementary to the enzyme’s active site.
How do competitive inhibitors prevent enzyme activity?
They block the active site so no substrate molecule can fit in, so no reaction takes place.
What does competitive inhibition depend on?
The relative concentrations of the substrate and the inhibitor.
What happens if substrate concentration is higher than competitive inhibitor concentration?
The substrate’s chances of getting to an active site before an inhibitor increases.
What happens if there is a higher concentration of competitive inhibitor than substrate?
The inhibitor will take up nearly all of the active sites and hardly any substrate will react.
What does competitive inhibition look like?
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What does a graph showing the effect on a competitive inhibitor on the rate of an enzyme-controlled reaction look like?
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How do non-competitive inhibitors prevent enzyme activity?
They cause the enzyme’s active site to change permanently so substrates can no longer bind.
How do non-competitive inhibitors permanently change the enzyme’s active site?
- They bind to the enzyme at the allosteric site (away from the enzyme’s active site).
- This changes the tertiary structure of the active site.
What happens when substrate concentration is higher than non-competitive inhibitor concentration?
This has no effect as non-competitive inhibitors don’t compete with substrate molecules to bind to the enzyme’s active site as they are a different shape.
Which inhibitor is best at its job?
Non-competitive inhibitors because their inhibition is permanent.
What does non-competitive inhibition look like?
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What does a graph showing the effect of a non-competitive inhibitor on the rate of an enzyme-controlled reaction look like?
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