10 questions🇬🇧English
🔑 Enzymes & Inhibition – A-level
Biology · A-level — practise the induced-fit model, factors affecting rate, denaturation and types of enzyme inhibition.
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Questions
Which level of protein structure gives an enzyme's active site its specific three-dimensional shape?
Primary structure
Quaternary structure
Tertiary structure
Secondary structure
20s
How do enzymes increase the rate of a reaction?
They increase the energy released overall
They lower the activation energy
They raise the temperature of the mixture
They raise the kinetic energy of substrates
20s
Which statement best describes the induced-fit model of enzyme action?
The active site changes shape slightly as substrate binds
The enzyme permanently changes shape after reacting
The substrate changes shape to fit a fixed active site
The active site is rigid and exactly fits the substrate
20s
Why does the rate of an enzyme-controlled reaction fall sharply above the optimum temperature?
Substrates move too fast to enter the active site
Enzyme molecules have less kinetic energy
Peptide bonds in the enzyme are hydrolysed
Bonds holding the tertiary structure break
30s
How does a pH far from the optimum denature an enzyme?
It directly raises the activation energy needed
It lowers the kinetic energy of the molecules
It alters charges on R groups, breaking ionic and H bonds
It hydrolyses the peptide bonds in the enzyme
30s
With a fixed amount of enzyme, why does the rate level off at high substrate concentration?
Excess substrate denatures the enzyme
Substrate molecules collide less often
The product has used up all the enzyme
All active sites are occupied at any one time
30s
A competitive inhibitor is added. What happens to the rate at a very high substrate concentration?
It falls to zero however much substrate is added
It reaches the same Vmax as without inhibitor
It reaches a lower Vmax than without inhibitor
It reaches a higher Vmax than without inhibitor
30s
With an inhibitor present, the maximum rate stays lower even at very high substrate concentration. What is the best explanation?
An activator binds at an allosteric site
A competitive inhibitor binds to the active site
Excess substrate is denaturing the enzyme
A non-competitive inhibitor binds at an allosteric site
30s
In end-product inhibition of a metabolic pathway, the final product usually:
Inhibits an enzyme early in the pathway
Inhibits only the last enzyme in the pathway
Permanently denatures enzymes in the pathway
Activates the first enzyme in the pathway
30s
An enzyme's rate is 0.8 units at 25 °C and 1.8 units at 35 °C. What is the temperature coefficient (Q₁₀)?
1.00
2.25
1.80
0.44
60s