Enzymes. Flashcards
What is a catalyst (1 mark)?
A catalyst is a substance that increases the rate of a chemical reaction and is not changed by the reaction.
What is an enzyme (1 mark).
An enzyme is a protein that functions as a biological catalyst.
Why are enzymes important (1 mark)?
Enzymes are necessary to all living organisms as they maintain reaction speeds of all metabolic reactions at a rate that can sustain life.
Describe enzyme action with reference to
the complementary shape of an enzyme and
its substrate and the formation of a product (3 marks).
Enzymes are specific to one particular substrate as the enzyme is a complementary shape to the substrate. The enzyme changes the substrate into new molecules called products.
Describe the effect on enzyme activity when the temperature is up to the enzyme’s optimum (4 mark).
As temperature increases to the optimum, the kinetic energy of the enzyme and substrate increases, causing more collisions between the enzyme and substrate. This causes the formation of more enzyme-substrate complexes, leading to an increase in enzyme activity.
Describe the effect on enzyme activity when the temperature is above the optimum (3 marks).
At very high temperatures above the optimum, the enzymes become denatured and the active site changes shape. This decreases the rate of reaction as enzyme-substrate complexes cannot form.
Describe the effect on enzyme activity when the temperature is below the optimum (3 mark).
At low temperatures, enzyme activity is low because the enzyme and substrate molecules have less kinetic energy so there are fewer collisions between them.
Describe the effect on enzyme activity when deviating from the optimum pH (4 marks).
Deviating from the optimum pH (too high or too low) causes the enzyme’s active site to become denatured. Hence, it can no longer form enzyme-substrate complexes, leading to a decrease in enzyme activity.
Explain the specificity of enzymes in terms of the
complementary shape and fit of the active site
with the substrate (3 marks).
Enzymes are specific because different enzymes have different shaped active sites. The shape of an enzyme’s active site is complementary to the shape of its specific substrate or substrates. This means they can fit together.
Explain enzyme action with reference to the
active site, enzyme-substrate complex, substrate
and product (5 marks).
A substrate enters the active site of the enzyme. This forms the enzyme-substrate complex. The reaction then occurs, converting the substrate into products and forming an enzyme products complex. The products then leave the active site of the enzyme.
