Factors affecting Enzyme Action Flashcards
Explain why a mutation in the gene that codes for an enzyme could potentially result in the formation of a non-functional enzyme.
The sequence of bases determines the primary structure of a protein
If the sequence of bases in a gene changes, the sequence of amino acids of a protein could also change
If the primary structure changes then the tertiary structure could change.
Any change in the tertiary structure could change the shape of the active site
Meaning the substrate is no longer complementary in shape to the active site Meaning no enzyme -substrate complexes can be formed.
Explain why an increase in temperature can increase the rate of an enzyme-catalysed reaction.
An increase in temperature increases the kinetic energy of the enzyme and substrate molecules, meaning the molecules are moving faster. This means that the chance of a successful collision between the substrate molecule and the enzymes active site is higher, resulting in more enzyme-substrate complexes being formed = a faster rate of reaction.
Explain why an increase in temperature can decrease the rate of an enzyme-catalysed reaction.
Above optimum temperature enzyme vibrates more
vibrations break the hydrogen bonds and ionic bonds in the tertiary structure of the enzyme
active site changes shape
substrate is no longer complementary in shape to the active site, meaning no enzyme -substrate complexes can be formed. The enzyme is denatured.
Explain the effects of any deviation away from the optimum pH on the rate of an enzyme-controlled reaction.
Deviation above or below an enzymes optimum pH reduces rate of reaction
H+ ions and OH- ions in acids and alkalis break hydrogen bonds and the ionic bonds in the tertiary structure of the enzyme
Active site changes shape
Substrate no longer complementary to the active site, meaning no enzyme -substrate complexes can be formed. The enzyme is denatured.
Describe and explain the effect of increasing substrate concentration on the rate of an enzyme-catalysed reaction.
Initially as concentration of substrate increases rate of reaction increases
Increasing the number of substrate molecules increases the chance of a successful collision with enzyme, resulting in the formation of an enzyme-substrate complex.
Above a given substrate concentration rate of reaction plateau’s
All of the active sites are full with substrate molecules, and so adding more substrate molecules makes no difference. At this point enzyme concentration is the limiting factor.
Describe and explain the effect of increasing enzyme concentration on the rate of an enzyme-catalysed reaction.
Initially as enzyme concentration increases rate of reaction increases.
Increasing the number of enzyme molecules increases the chance of a successful collision with a substrate, resulting in the formation of an enzyme-substrate complex.
Above a given concentration of enzyme rate of reaction plateau’s, this is because the concentration of substrate is the limiting factor.
Explain how a competitive inhibitor works.
Competitive inhibitor molecules have a similar shape to the substrate molecule.
They compete with the substrate for the active site, and will temporarily bind to the active site stopping the substrate from binding, reducing the rate of reaction.
Increasing the concentration of the substrate will increase of the rate of reaction.
Explain how a non-competitive inhibitor works.
Non-competitive inhibitor molecules bind to the enzyme away from the active site (at the allosteric site)
Active site changes shape, meaning the shape of the substrate is no longer complementary to the active site and so can not bind and form an enzyme-substrate complex.
Increasing the concentration of the substrate will no impact of the rate of reaction.
Describe two ways in which you can measure the rate of an enzyme-catalysed reaction.
You can measure the rate of a reaction by measuring how quickly the substrate is broken down OR how quickly the product is made.
Describe how you can calculate the initial rate of a reaction from a graph.
Draw a tangent on the curve using a ruler at time = 0. Then calculate the gradient of the tangent = change in y/change in x
If you are testing the effect of temperature on an enzyme-catalysed reaction, what other variables would you keep the same?
pH (use a buffer), substrate concentration and enzyme concentration.
