intro
MCQs 1:
What temperature does most enzymes function optimally at?
Topic: Enzyme Activity and Temperature
Correct Answer: B) Optimum
- Enzymes, being biological catalysts, perform best at an 'optimum' temperature.
- At 'maximum' or 'minimum' temperatures, enzyme activity may be hindered due to denaturation or inactivity, respectively.
- 'Same at all' is incorrect as temperature significantly affects enzyme activity.
- Therefore, the correct answer is B, "Optimum".
MCQs 2:
Considering an equal amount of enzyme and substrate, what will be the effect on the rate of reaction if additional enzymes are introduced?
Topic: Enzyme-Substrate Interaction
Correct Answer: C) No effect
- The rate of reaction in a system with an equal quantity of enzyme and substrate remains unchanged if more enzymes are added.
- The reaction rate only increases when there's a surplus of substrate for the additional enzymes.
- If the substrate quantity is greater than the enzyme quantity, the reaction rate increases with enzyme addition.
- Hence, the correct response is C, "No effect".
MCQs 3:
Which type of inhibitor has the potential to completely destroy the active site of an enzyme?
Topic: Enzyme Inhibitors
Correct Answer: A) Competitive
- A competitive inhibitor binds to the enzyme's active site, altering its structure and function.
- Non-competitive inhibitors do not destroy the active site; they bind to other parts of the enzyme, changing its shape and reducing its effectiveness.
- The correct answer is A, "Competitive".
MCQs 4:
Which part of the enzyme can accommodate both the substrate and the inhibitor?
Topic: Enzyme Binding Sites
Correct Answer: A) Active site
- The active site of an enzyme is where the substrate and competitive inhibitor can both bind.
- The allosteric site is another part of the enzyme where only a non-competitive inhibitor can bind, not the substrate.
- Thus, the correct answer is A, "Active site".
MCQs 5:
Emil Fischer, in 1890, proposed that the structure of an enzyme's active site is...?
Topic: Structure of Enzyme Active Sites
Correct Answer: B) Rigid
- Emil Fischer presented the Lock & Key Model, suggesting the enzyme's structure, particularly the active site, as rigid.
- In contrast, Kosh Land's Induced Fit Model proposes the enzyme as slightly flexible.
- Therefore, the accurate response is B, "Rigid".
MCQs 6:
What is the optimal pH range for most enzyme activity?
Topic: pH and Enzyme Activity
Correct Answer: C) 7 to 8
- Enzymes typically function best at a slightly alkaline pH range, specifically from 7 to 8.
- Outside this range, enzyme activity may decrease due to changes in their structure.
- Consequently, the appropriate answer is C, "7 to 8".
MCQs 7:
How is the rate of an enzymatic reaction affected if the temperature is increased within a certain limit?
Topic: Temperature and Enzyme Activity
Correct Answer: A) Increases
- Within a specific limit, a rise in temperature boosts the kinetic energy and the collision frequency between the enzyme and substrate, thus increasing the reaction rate.
- However, if the temperature increases beyond this limit, the enzyme may denature, decreasing the reaction rate.
- Hence, the correct answer is A, "Increases".
Question 8:
What part of the enzyme is predominantly affected by pH?
Topic: pH and Enzyme Function
Correct Answer: A) Active site charge
- pH influences the ionization of the active site, which is crucial for enzyme-substrate interaction.
- While pH may have some impact on the allosteric site and substrate, the primary effect is on the active site charge.
- Therefore, the correct answer is A, "Active site charge".
Question 9:
Where does the substrate attach during an enzymatic reaction?
Topic: Enzyme-Substrate Binding
Correct Answer: A) Active site
- The substrate binds to the active site of an enzyme during a reaction, where catalysis occurs.
- The allosteric site is another region on the enzyme, but the substrate does not bind there.
- Thus, the correct answer is A, "Active site".
Question 10:
What happens to enzymatic reaction rate if the temperature of a human body cell increases from 35 degrees to 45 degrees Celsius?
Topic: Temperature and Enzyme Activity
Correct Answer: D) Enzyme denatures
- The rate of an enzymatic reaction increases with temperature, but only up to a certain point.
- For human body cells, the enzymes function optimally up to about 40°C. Beyond this, an increase in temperature denatures the enzymes, consequently decreasing the reaction rate.
- Hence, the correct answer is D, "Enzyme denatures".
Question 11:
Why does the rate of a reaction generally increase with rising temperature?
Topic: Temperature and Reaction Rate
Correct Answer: C) Both enzyme and substrate exhibit increased kinetic energy
- Increasing the temperature generally boosts the kinetic energy of both the enzyme and the substrate.
- The heightened kinetic energy leads to more frequent collisions between the enzyme and the substrate.
- Consequently, the rate of reaction generally increases with rising temperature. The correct answer is thus C, "Both enzyme and substrate exhibit increased kinetic energy".
Question 12:
Assume the temperature rises by 10 degrees, what will likely happen to the rate of the reaction?
Topic: Temperature and Reaction Rate
Correct Answer: C) The rate will be doubled
- Generally, for every 10-degree Celsius increase in temperature, the rate of the reaction doubles.
- This rule applies within certain limits, beyond which the rate may decrease due to enzyme denaturation.
- Hence, the correct answer is C, "The rate will be doubled".
Question 13:
Which of the following statements accurately describes the active site of an enzyme?
Topic: Enzyme Active Site
Correct Answer: D) All of the above are correct
- The active site of an enzyme is composed of amino acids and includes two main parts: the binding site and the catalytic site.
- The binding site is where the enzyme holds the substrate, while the catalytic site is where the reaction occurs.
- Therefore, all statements are true, making the correct response D, "All of the above are correct".
Question 14:
Where do competitive inhibitors primarily bind on an enzyme?
Topic: Competitive Inhibitors
Correct Answer: A) Active site
- Competitive inhibitors are molecules with a shape similar to the substrate, enabling them to compete for the enzyme's active site.
- Upon binding, these inhibitors prevent the substrate from attaching to the active site, thus inhibiting the reaction.
- The correct answer is therefore A, "Active site".
Question 15:
Which factor is the most specific in affecting the reaction rate?
Topic: Factors Affecting Reaction Rate
Correct Answer: A) pH level
- Although all the factors listed can influence the rate of reaction, the pH level is the most specific.
- Changes in pH can alter the charge of the amino acids at the enzyme's active site, significantly affecting the rate of reaction.
- Therefore, the correct answer is A, "pH level".
Question 16:
During feedback inhibition, where does the inhibitor primarily bind?
Topic: Feedback Inhibition
Correct Answer: B) Allosteric site
- Feedback inhibition involves an inhibitor binding to a site on the enzyme other than the active site, known as the allosteric site.
- This binding causes a shape change in the enzyme, preventing substrate binding at the active site.
- Hence, the correct answer is B, "Allosteric site".
Question 17:
What happens to the reaction rate if the substrate concentration increases and sufficient enzymes are available?
Topic: Substrate Concentration and Reaction Rate
Correct Answer: A) It increases
- When more substrate is present and there are enough enzymes to facilitate the reaction, the reaction rate tends to increase.
- This is because there are more substrate molecules available for enzymes to bind to and convert into the product.
- Consequently, the correct response is A, "It increases".
Question 18:
Assuming a fixed enzyme concentration, what is the effect of increasing the substrate concentration on the reaction rate once maximum capacity is reached?
Topic: Enzyme Saturation
Correct Answer: C) It remains the same
- When all enzymes are bound with substrates (enzyme saturation), increasing the substrate concentration further will not affect the reaction rate.
- This is because there are no free enzymes left to process the additional substrate.
- Therefore, the correct choice is C, "It remains the same".
Question 19:
If the concentration of the enzyme is doubled while the substrate concentration remains constant, what would be the effect on the reaction rate?
Topic: Enzyme Concentration and Reaction Rate
Correct Answer: A) It increases
- Higher enzyme concentration means more active sites are available to bind with the substrate.
- Consequently, the reaction rate increases because there are more opportunities for the enzyme-substrate interaction.
- As a result, the correct choice is A, "It increases".