Question
Lactose can be removed from milk by passing the milk through a column of alginate beads to which immobilized lactase is bound. What is an advantage of immobilizing the enzyme?
A. It creates more active sites.
B. The alginate beads act as a coenzyme.
C. It lowers the activation energy of the reaction.
D. It allows the product to be separated easily from the enzyme.
▶️Answer/Explanation
Answer: D. It allows the product to be separated easily from the enzyme.
Explanation:
Immobilizing an enzyme means attaching it to a solid support, like alginate beads. This keeps the enzyme in one place so the milk can flow over it, and lactose is broken down to simpler sugars.
Option Evaluation:
A. Incorrect – Immobilizing doesn’t increase the number of active sites; it just keeps the enzyme fixed in one spot.
B. Incorrect – Alginate beads are just a support matrix; they do not act as a coenzyme.
C. Incorrect – Lowering activation energy is the role of the enzyme itself, not affected by immobilization.
D. Correct – Immobilizing lactase makes it easy to separate the enzyme from the milk after the reaction, allowing reuse and preventing enzyme contamination in the product.
Question
What is the advantage of using lactase in an immobilized state in the food manufacturing industry?
A. It functions within cells.
B. It dissolves in multiple solvents.
C. It converts cellulose into glucose.
D. It is less likely to become denatured.
▶️Answer/Explanation
Answer: D. It is less likely to become denatured.
Explanation:
Immobilizing lactase means attaching the enzyme to a solid support, which helps keep its shape stable. This reduces the chance of the enzyme losing its structure (denaturation) due to changes in temperature, pH, or other conditions during food processing. A more stable enzyme can be reused many times, making the process more efficient and cost-effective.
Options Evaluation:
A. Incorrect – Lactase used in industry is usually outside cells (extracellular) and immobilized to improve stability, not functioning inside cells.
B. Incorrect – Lactase does not dissolve in multiple solvents; it works best in aqueous environments.
C. Incorrect – Lactase breaks down lactose into glucose and galactose, not cellulose. Cellulose is broken down by cellulase.
D. Correct – Immobilizing lactase helps it resist denaturation, keeping it active longer during manufacturing.
Question
What effect do changes in pH have on enzymes?
A. All enzymes increase in activity as pH increases.
B. The activity of all enzymes is reduced by a pH below or above 7.
C. Low pH causes reversible denaturation in all enzymes.
D. Extreme pH can alter the active site of all enzymes.
▶️Answer/Explanation
Answer: D. Extreme pH can alter the active site of all enzymes.
Explanation:
Enzymes have an optimal pH at which they work best. When the pH is too high or too low (extreme pH), it can change the shape of the enzyme, especially the active site where the substrate binds. This change can stop the enzyme from working properly. This process is often called denaturation, and it can be reversible or irreversible depending on the enzyme and conditions.
Options Evaluation:
A. Incorrect – Not all enzymes increase activity as pH increases; many have specific optimal pH values, often different from neutral 7.
B. Incorrect – Enzymes have different optimal pH values; some work best below or above 7, so activity is not always reduced outside pH 7.
C. Incorrect – Low pH may cause denaturation in some enzymes, but not all, and denaturation is not always reversible.
D. Correct – Extreme pH levels can change the shape of the active site in all enzymes, reducing or stopping their activity.
Question
What is a common feature of enzymes?
A. They all react with substrates.
B. They all decrease the rate of reaction.
C. They are all secreted from cells in vesicles.
D. They all bind to the active site of their substrate.
▶️Answer/Explanation
Answer: A. They all react with substrates.
Explanation:
Enzymes are biological catalysts that speed up chemical reactions by reacting specifically with substrates—the molecules they act upon. Each enzyme has an active site where the substrate binds, allowing the enzyme to carry out its function efficiently. However, enzymes do not bind to the active site of their substrate (the substrate fits into the enzyme’s active site, not the other way around).
Options Evaluation:
A. Correct – Enzymes always react with substrates, which are the molecules they catalyze.
B. Incorrect – Enzymes increase the rate of reactions; they do not decrease it.
C. Incorrect – Not all enzymes are secreted from cells or packaged in vesicles; many function inside cells.
D. Incorrect – Enzymes have an active site where substrates bind, but enzymes do not bind to a substrate’s active site.
Question
The graph shows the activity of an enzyme at different temperatures.
What does the dashed line in the graph represent?
A. Increasing temperature increases substrate concentration.
B. Increasing temperature affects the active site.
C. Increasing temperature increases the rate of reaction.
D. Increasing temperature decreases the movement of particles.
▶️Answer/Explanation
Answer: B. Increasing temperature affects the active site.
Explanation:
- The dashed line shows a steady increase in rate with temperature — this is the expected trend if temperature only affected particle movement (i.e., without enzyme denaturation).
- However, the solid curve peaks and then falls. This shows that:
- Initially, the enzyme activity increases with temperature.
- After a certain point, the rate drops sharply. This indicates the enzyme becomes denatured — its active site changes shape and can no longer bind the substrate effectively.
- So, the dashed line is a reference curve, and the difference between it and the real curve (solid line) is because temperature affects the enzyme’s active site at higher temperatures.
Key point:
High temperatures denature enzymes, meaning the active site is altered, which reduces or stops enzyme activity.
Question
In which processes are macromolecules broken down into monomers?
A. Anabolism and catabolism
B. Catabolism and hydrolysis
C. Hydrolysis and reduction
D. Reduction and anabolism
▶️Answer/Explanation
Answer: B. Catabolism and hydrolysis
Explanation:
Macromolecules (like proteins, carbohydrates, and nucleic acids) are large molecules made of smaller building blocks called monomers. Breaking them down into monomers happens during catabolic processes and specifically through hydrolysis reactions.
- Catabolism is the general term for all breakdown reactions in the body.
- Hydrolysis is the specific chemical process where water is used to break bonds between monomers.
Options Evaluation:
A. Incorrect – Anabolism builds macromolecules; it’s the opposite of breaking down.
B. Correct – Catabolism (general breakdown) and hydrolysis (specific method) both describe breaking macromolecules into monomers.
C. Incorrect – Reduction refers to gain of electrons and has nothing to do with breaking down macromolecules.
D. Incorrect – Both reduction and anabolism are not related to breaking molecules down; anabolism builds them up.
Question
Which process is an example of catabolism?
A. Translation of mRNA
B. Replication of DNA
C. Hydrolysis of protein
D. Synthesis of a disaccharide
▶️Answer/Explanation
Answer: C. Hydrolysis of protein
Explanation:
Catabolism refers to the breakdown of large molecules into smaller ones. These reactions release energy and often involve hydrolysis, where water is used to break chemical bonds.
In this case:
Breaking down a protein into amino acids by adding water is a clear example of catabolism and hydrolysis.
Options Evaluation:
A. Incorrect – Translation of mRNA is an anabolic process where amino acids are joined to form proteins.
B. Incorrect – Replication of DNA builds a copy of DNA, so it’s anabolic (building up).
C. Correct – Hydrolysis of protein breaks it down into amino acids, which is a catabolic process.
D. Incorrect – Synthesis of a disaccharide (like joining glucose units) is an anabolic reaction (building molecules).
Question
The graph shows the activity of an enzyme at various temperatures. The pH of the experiment was kept constant at pH 8.
Based on the data, what would the result be if the experiment was repeated at pH 9?
A. The enzyme activity would be higher.
B. The results of the enzyme activity would be almost the same.
C. The enzyme activity would be lower.
D. There is not enough information to make a reliable prediction.
▶️Answer/Explanation
Answer: C. The enzyme activity would be lower.
Explanation:
Enzymes work best at a specific optimal pH, where their active site has the perfect shape and charge to bind the substrate. In the given experiment, pH 8 appears to be this optimum.
If the experiment is repeated at pH 9, the environment becomes more alkaline, moving away from the optimum. This shift can:
- Change the charge on amino acids in the active site
- Slightly alter the shape of the enzyme
- Reduce substrate binding and lower catalytic efficiency
Even a small change in pH can significantly affect enzyme function because enzyme structure is sensitive to pH levels.
Options Evaluation:
A. Incorrect – The enzyme already shows high activity at pH 8. Increasing to pH 9 likely moves away from the optimal, not toward it.
B. Incorrect – Enzymes are very sensitive to pH changes. Even a one-unit change can noticeably reduce activity.
C. Correct – Moving from pH 8 to pH 9 would likely lower enzyme activity due to slight denaturation or reduced substrate binding.
D. Incorrect – The enzyme’s peak at pH 8 provides enough data to predict the effect of changing to pH 9.
Question
The graph shows the results of an investigation into the activity of turnip peroxidase. The accumulation of the product of the reaction catalysed by the enzyme is shown at different pH values.
Based on the data in the graph, what is most probably the optimum pH for turnip peroxidase?
A. Between 3 and 5
B. Between 10 and 11
C. Between 7 and 8
D. Between 9 and 10
▶️Answer/Explanation
Answer: C. Between 7 and 8
Explanation:
The graph shows the concentration of product over time at different pH values for the enzyme turnip peroxidase. The steeper the line, the faster the rate of reaction and thus higher enzyme activity.
- The steepest line is at pH 7, indicating the highest rate of product formation.
- Enzyme activity decreases at both lower and higher pH values compared to pH 7.
- This suggests that pH 7 is the optimum pH, and the enzyme likely maintains high activity just slightly beyond pH 7 as well (hence the range 7–8).
Options Evaluation:
A. Incorrect – pH 3–5 shows very low enzyme activity.
B. Incorrect – Activity at pH 10 and above is lower than at pH 7.
C. Correct – The graph shows maximum product formation at pH 7, making 7–8 the most probable optimum pH range.
D. Incorrect – While pH 9 shows decent activity, it’s not the peak.