Description: Practice Class 11 Biology Chapter 3 Enzymes MCQs according to the FBISE HSSC-I assessment framework. Questions cover enzyme action, active sites, enzyme-substrate complexes, activation energy, temperature, pH, substrate concentration, inhibition, cofactors and industrial applications.
1. Enzymes are biological catalysts that generally:
A) Slow down all reactionsB) Increase the rate of biochemical reactionsC) Are consumed permanently in reactionsD) Replace DNA
2. Most enzymes are:
A) ProteinsB) LipidsC) CarbohydratesD) Nucleic acids
3. The region of an enzyme where the substrate binds is called the:
A) Active siteB) Cell wallC) NucleoidD) Phospholipid layer
4. The molecule upon which an enzyme acts is called the:
A) ProductB) SubstrateC) CofactorD) Inhibitor
5. The substances formed at the end of an enzyme-catalysed reaction are called:
A) SubstratesB) ProductsC) CofactorsD) Buffers
6. The enzyme-substrate complex forms when:
A) An enzyme binds its substrateB) An enzyme is destroyedC) A product binds to DNAD) ATP is removed from the cell
7. The induced-fit model proposes that:
A) The active site can change shape slightly when the substrate bindsB) Enzymes have no specific substratesC) Substrates permanently change into enzymesD) Enzymes are made only of lipids
8. The lock-and-key model emphasizes the:
A) Complementary shape of enzyme active site and substrateB) Random movement of enzymesC) Breakdown of DNAD) Formation of cell walls
9. Enzyme specificity is mainly related to the:
A) Shape and chemical properties of the active siteB) Colour of the enzymeC) Size of the cellD) Number of chromosomes
10. An enzyme lowers the:
A) Activation energy of a reactionB) Temperature of the environmentC) Number of products formedD) Amount of substrate permanently
11. Activation energy is the minimum energy required to:
A) Start a chemical reactionB) Stop diffusionC) Form a chromosomeD) Destroy every enzyme
12. Enzymes speed reactions without being:
A) Permanently consumedB) ProteinsC) SpecificD) Reusable
13. The rate of an enzyme-catalysed reaction usually increases with substrate concentration until:
A) The enzymes become saturatedB) All substrate disappears instantlyC) Temperature becomes zeroD) pH becomes neutral
14. At enzyme saturation, most active sites are:
A) Occupied by substrateB) DestroyedC) Filled with water onlyD) Converted into products
15. If enzyme concentration is increased while substrate is abundant, reaction rate generally:
A) IncreasesB) Always becomes zeroC) Remains unchanged in every situationD) Decreases to zero
16. The optimum temperature is the temperature at which an enzyme:
A) Shows maximum activity under stated conditionsB) Is always denaturedC) Stops binding substrateD) Is converted into lipid
17. At very high temperatures, many enzymes lose activity because they:
A) Become denaturedB) Gain more active sitesC) Turn into carbohydratesD) Increase their amino acid sequence
18. Denaturation commonly changes an enzyme’s:
A) Three-dimensional structureB) Atomic number of carbonC) Genetic code of the organismD) Number of chromosomes
19. At low temperatures, enzyme activity usually decreases because molecules:
A) Have less kinetic energy and collide less frequentlyB) Are always denaturedC) Become radioactiveD) Lose all hydrogen atoms
20. The optimum pH is the pH at which an enzyme:
A) Has its maximum activity under specified conditionsB) Is always denaturedC) Cannot bind substrateD) Is converted to DNA
21. A change in pH can affect an enzyme by altering:
A) Ionic interactions and the shape of its active siteB) The number of cells in the organismC) The mass of every atomD) The sequence of chromosomes only
22. Pepsin functions most effectively in a:
A) Strongly acidic environmentB) Strongly alkaline environmentC) Completely dry environmentD) Neutral salt crystal
23. Amylase catalyses the digestion of:
A) StarchB) LipidsC) ProteinsD) DNA only
24. Protease enzymes catalyse the breakdown of:
A) ProteinsB) StarchC) Lipids onlyD) Water
25. Lipase catalyses the breakdown of:
A) LipidsB) ProteinsC) Cellulose onlyD) DNA
26. Catalase catalyses the breakdown of:
A) Hydrogen peroxideB) Glucose into starchC) DNA into lipidsD) Cellulose into protein
27. The products of catalase activity include:
A) Water and oxygenB) Glucose and starchC) Amino acids and DNAD) Carbon dioxide and nitrogen
28. A cofactor is a:
A) Non-protein component required by some enzymes for activityB) Product of every reactionC) Type of carbohydrateD) Type of cell membrane
29. A coenzyme is generally an:
A) Organic non-protein helper moleculeB) Inorganic salt onlyC) Enzyme substrate onlyD) Structural carbohydrate
30. Many vitamins are important because they can serve as precursors of:
A) CoenzymesB) Cellulose fibresC) Phospholipid tailsD) DNA chromosomes
31. An apoenzyme is the:
A) Protein part of an enzyme lacking its required cofactorB) Complete active enzyme with every componentC) Substrate of an enzymeD) Product of hydrolysis
32. A holoenzyme is:
A) The complete active enzyme including its required non-protein componentB) An inactive protein onlyC) A substrate moleculeD) A polysaccharide
33. Competitive inhibition occurs when an inhibitor:
A) Competes with substrate for the active siteB) Permanently increases enzyme activityC) Binds only to DNAD) Converts substrate into enzyme
34. A competitive inhibitor can often be overcome by:
A) Increasing substrate concentrationB) Removing all substrateC) Lowering enzyme concentration to zeroD) Destroying the active site
35. Non-competitive inhibition generally involves an inhibitor binding:
A) At a site other than the active siteB) Only to the substrateC) Only to waterD) To a ribosome
36. An allosteric site is a site on an enzyme:
A) Distinct from the active site where a regulator may bindB) Where DNA is replicatedC) Where glucose is storedD) Found only in cell walls
37. Feedback inhibition occurs when:
A) A final product inhibits an earlier enzyme in a metabolic pathwayB) A substrate always destroys an enzymeC) Water inhibits all reactionsD) Oxygen stops every pathway
38. Enzyme inhibitors are useful in cells because they can:
A) Regulate metabolic pathwaysB) Prevent all metabolism permanentlyC) Replace all enzymesD) Produce chromosomes
39. Irreversible inhibitors generally:
A) Permanently inactivate an enzymeB) Always increase enzyme activityC) Act only as substratesD) Are always removed by dilution
40. Reversible inhibitors usually bind to enzymes through:
A) Interactions that can be disrupted under suitable conditionsB) Permanent destruction of every peptide bondC) Formation of a new chromosomeD) Conversion into glucose
41. Enzyme activity can be measured by determining the:
A) Rate of product formation or substrate disappearanceB) Number of chromosomesC) Colour of the organismD) Size of the nucleus only
42. If product is formed rapidly during an enzyme assay, the enzyme has a:
A) High reaction rate under those conditionsB) Zero activityC) Low substrate concentration by definitionD) Permanently denatured structure
43. Immobilized enzymes are enzymes that are:
A) Attached to or trapped within an insoluble materialB) Always denaturedC) Present only inside nucleiD) Converted into DNA
44. An advantage of immobilized enzymes in industry is that they can often be:
A) Recovered and reusedB) Destroyed after one reactionC) Used without substrateD) Converted into vitamins
45. Immobilized enzymes can make industrial processing easier because they:
A) Can be separated from the reaction mixtureB) Eliminate all productsC) Never require suitable conditionsD) Cannot catalyse reactions
46. Lactase is used industrially to hydrolyse:
A) LactoseB) StarchC) CelluloseD) Protein
47. The hydrolysis of lactose by lactase produces:
A) Glucose and galactoseB) Glucose and fructoseC) Amino acidsD) Fatty acids
48. Pectinase is used in food processing to help clarify:
A) Fruit juicesB) Blood plasmaC) DNA samplesD) Mineral ores
49. Enzymes are useful in biological washing powders because they can break down:
A) Protein, lipid and carbohydrate stainsB) DNA chromosomes onlyC) Cell membranes of all cellsD) Metals
50. The use of enzymes in biotechnology is based mainly on their ability to:
A) Catalyse specific biochemical reactionsB) Produce energy without substratesC) Function independently of all conditionsD) Replace every cellular organelle
Syllabus: This chapter covers the key concepts and topics prescribed by the FBISE Grade 11 Biology syllabus, including enzyme action, active sites, enzyme-substrate complexes, activation energy, factors affecting enzyme activity, inhibition, cofactors, and industrial applications.
SLO Alignment: These MCQs are designed to assess the relevant FBISE Student Learning Outcomes (SLOs) through knowledge, understanding, and application of the concepts covered in this chapter.