Enzymes MCQs / Quizzes and SQs

Enzymes MCQs / Quizzes and SQs (School)

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MCQs / Quiz

1. Which is TRUE about enzymes?

1. They make biochemical reactions to proceed spontaneously
2. They lower the activation energy of a reaction
3. They are not very specific in their choice of substrates
4. They are needed in large quantities

2. To what category of molecules do enzymes belong? / Chemically enzymes are:

1. Carbohydrates
2. Lipids
3. Nucleic acid
4. Proteins

3. What is true about cofactors?

1. Break hydrogen bonds in protein
2. Help facilitate enzyme activity
3. Increase activation energy
4. Are composed of proteins

4. Prosthetic groups are:

1. Required by all enzymes
2. Loosely attached with enzymes
3. Proteins in nature
4. Tightly bound to enzyme

5. Medium in which enzyme trypsin works:

1. Alkaline
2. Acidic
3. Neutral
4. Strong acidic

6. Structurally enzymes are made of:

1. Minerals
2. Amino acids
3. Vitamins
4. Fats

7. The substance on which an enzyme acts is called:

1. Cofactor
2. Inhibitor
3. Coenzyme
4. Substrate

8. Non-protein part of enzyme are:

1. Inhibitors
2. Substrate
3. Cofactors
4. Coenzymes

9. Optimum temperature for enzymes of human body is:

1. 86^oC
2. 37^oC
3. 38^oC
4. 39^oC

10. Activation energy is required to:

1. Activate enzyme
2. Start a reaction
3. Speed up a reaction
4. Facilitate enzyme activity

11. Lock and key model was proposed by:

1. Emil Fischer
2. Meischer
3. Koshland
4. Saugeo

12. Induced fit model was proposed by:

1. Emil Fisher
2. Koshland
3. Meischer
4. Schleiden

13. Enzyme which breaks the peptide bonds:

1. Amylase
2. Protease
3. Lipase
4. Pepsin

14. Which enzyme converts lipids into fatty acid and glycerol?

1. Lipase
2. Amylase
3. Pepsin
4. Trypsin

15. Number of discovered enzymes are more than:

1. 200
2. 2000 ANS
3. 3000
4. 3500

16. Starch is broken down by enzyme called:

1. Lipase
2. Pepsin
3. Amylase
4. Protease

17. The active site of an enzyme:

1. Never changes
2. Forms no chemical bond with substrate
3. Determines by its structure the specificity of the enzyme
4. Looks like a lump projecting from the surface of an enzyme

18. Enzymes have all the characters EXCEPT:

1. They consist of proteins with or without a non-protein part
2. They change the rate of catalyzed reaction
3. They are sensitive to heat
4. They are non-specific in their action

19. The covalently bonded co-factors are:

1. Activators
2. Prosthetic group
3. Co-enzyme
4. Prosthetic group and coenzyme

20. Trypsin enzyme works in:

1. Stomach
2. Large intestine
3. Small intestine
4. Heart

21. Active site is:

1. the small catalytic region of enzyme molecule
2. non-charge bearing site
3. non-catalytic region of enzyme molecule
4. not a part of an enzyme

22. Enzyme always react with a specific substrate because of:

1. Specific shape of their active sites
2. Specific prosthetic group
3. Capability to form specific bonds
4. Specific coenzyme

23. Emil Fischer proposed the Lock and Key model in:

1. 1890
2. 1800
3. 1894 ANS
4. 1900

24. The concept of metabolism was first of all given by:

1. Jabir bin Hayan
2. Ibn e Nafees
3. Bu Ali Sina
4. Aristotle

25. All of the following are vitamins EXCEPT:

1. Riboflavin
2. Thiamine
3. Folic Acid
4. Heme

26. It helps in the transport of chemical groups from one enzyme to another?

1. Cofactors
2. Coenzymes
3. Enzymes
4. Prosthetic group

27. Enzyme activity can also be regulated by:

1. Inhibitors
2. Activators
3. Inhibitors and activators
4. Temperature above 37^oC

28. Cofactors are:

1. Protein molecules
2. Lipid molecules
3. Non-protein molecules
4. Starch molecules

29. Enzymes are used in:

1. Food industry
2. Brewing industry
3. Paper industry
4. All of the above

30. More acceptable model for enzyme is:

1. Induced Fit model
2. Lock and Key model
3. Induced Fit model and Lock and Key model
4. Enzyme substrate model

31. The biochemical reactions in which larger molecules are broken down are called:

1. Metabolism
2. Catabolism
3. Anabolism
4. Mutualism

32. Which of the following are not changed during the biochemical reactions?

1. Substrates
2. Products
3. Enzymes
4. ES complex

33. Pepsin is active in:

1. Acid
2. Base
3. Alkali
4. Neutral medium

34. Set of biochemical reactions that occur in living organisms in order to maintain life is called:

1. Catabolism
2. Anabolism
3. Metabolism
4. Mutualism

35. The biochemical reactions in which larger molecules are synthesized are called:

1. Anabolism
2. Metabolism
3. Catabolism
4. Digestive reactions

36. Lipase enzyme acts only on lipids and digests them into:

1. Fatty acids and glycerol
2. Glycerol
3. Fatty acids
4. Amino acids

37. When ES complex breaks, it releases:

1. Enzyme
2. Product
3. Substrate
4. Enzyme and product

38. Enzyme attaches with substrate to form:

1. Product
2. Reactant
3. ES complex
4. Active site

39. All enzymes work at their maximum rate at a narrow range of pH, called:

1. Optimum temperature
2. Optimum pH
3. Denaturation of enzyme
4. Saturation of active sites

40. When the active sites of all enzymes are occupied, any more substrate molecules do not find free active sites. This state is called:

1. Denaturation of enzyme
2. Saturation of active sites
3. Optimum pH
4. Optimum temperature

41. Example of globular proteins is:

1. Hormones
2. Enzymes
3. Cofactors
4. Prosthetic group

42. All biochemical catalysts are:

1. Lipids
2. Proteins
3. Carbohydrates
4. Fats

43. Enzymes are usually very specific for the:

1. Type of reaction
2. For the nature of their substrate
3. For the type of reaction and for the nature of their substrates
4. Rate of reaction

44. Only a small portion of enzyme molecule is directly involved in catalysis. This catalytic region is known is:

1. Inactive site
2. Active site
3. Non-reactive site
4. Active and inactive site

45. Nature of flavin as a cofactor is:

1. Inorganic
2. Metal ions
3. Organic
4. Metalloids

46. Nature of metal ion as a cofactor is:

1. Inorganic
2. Organic
3. Organic and inorganic
4. Metalloids

47. Which of the following are not vitamins?

1. Riboflavin
2. Thiamine
3. Folic acid
4. Flavin and heme

48. In paper making, starch is broken by enzyme to lower its:

1. Density
2. Viscosity
3. Mass
4. Weight

49. Enzymes are very __ to the environment in which they work:

1. Sensitive
2. Not sensitive
3. Sensitive and insensitive
4. Crucial

50. Ionization of amino acids at the active site is affected by:

1. Change in temperature
2. Change in substrate concentration
3. Change in pH
4. Change in temperature and substrate concentration

51. "The body and its parts parts are always undergoing change" it is stated by:

1. Winhelm Kuhne
2. Daniel Koshland
3. Emil Fischer
4. Ibn e Nafees

52. Term which is derived from a Greek word meaning change:

1. Anabolism
2. Catabolism
3. Metabolism
4. Enzymes

Short Questions

Q1. Define Activation energy. Write its role in enzyme action.

Ans. The minimum energy required to start a reaction. All chemical reactions require activation energy. The need for activation energy acts as barrier to the beginning of reaction.

Q2. What is meant by active site of an enzyme?

Ans. Only a small portion of enzyme molecule is directly involved in catalysis. This catalytic region is known as active site. It recognizes and binds substrate and then carries out reaction.

Q3. On what substrate does Amylase act?

Ans. Amylase is an enzyme which acts on starch and converts it into maltose.

Q4. Define Anabolism.

Ans. Anabolism is the total series of chemical reaction involved in the synthesis of compounds e.g. photosynthesis and assimilation.

Q5. Define Bio-catalysts.

Ans. Enzymes are known as bio-catalyst because they speed up and regulate the metabolic pathway in living organisms.

Q6. Define Catabolism.

Ans. Catabolism is the series of chemical reactions in which complex or large molecules are broken down e.g. respiration and digestion.

Q7. Define co-enzymes. Write their function.

Ans. If organic co-factors are loosely attached with enzyme they are called co-enzymes. Some important vitamins e.g. riboflavin, thiamin and folic acid act as coenzymes.

Q8. Define Co-factors.

Ans. Some enzymes require non-protein molecules or ions to work, these molecules or ions are called cofactors. Cofactors can be either inorganic e.g. metal ions or can be organic e.g. flavin.

Q9. What is denaturation of an enzyme.

Ans. When temperature is raised well above the optimum temperature, the heat energy increases the vibrations of atoms of enzyme molecules and the globular structure of enzyme is lost. This is known as denaturation of enzyme.

Q10. What is optimum pH of enzyme?

Ans. All enzymes work at their maximum rate at a narrow range of pH, called as the optimum pH e.g. pepsin is active in acidic medium (low pH).

Q11. What is optimum temperature of enzyme?

Ans. Every enzyme works at its maximum rate at a specific temperature called as the optimum temperature for that enzyme e.g. optimum temperature for the maximum working speed of human enzymes is 37^oC.

Q12. Define enzymes.

Ans. Enzymes are proteins that catalyzes (i.e. speed up) biochemical reaction and are not changed during the reaction.

Q13. What is enzyme substrate complex?

Ans. When enzyme attaches with the substrate, a temporary enzyme substrate complex (ES) is formed. The enzyme catalyzes the reaction, substrate is transformed into product, the (ES) complex breaks and enzyme and product are released.

Q14. Give function of lipase.

Ans. Lipase is the enzyme which acts on lipids and digest them into fatty acids and glycerol.

Q15. Describe Lock and Key Model.

Ans. In order to explain the mechanism of enzyme action, a German Chemist Emil Fischer, in 1894 proposed the Lock and Key model. According to his model, both the enzyme and the substrate possess specific shapes, that fit exactly into one another. This model explains enzyme specificity.

Q16. Define Metabolism. Who gave the concept of metabolism.

Ans. Metabolism is the set of biochemical reactions that occur in living organism in order to maintain life. It is of two types: anabolism and catabolism. The concept of metabolism was given by Ibn-e-Nafees.

Q17. What do you mean by saturation of active sites?

Ans. When all the active sites of the enzymes are occupied (at high substrate concentration) any more substrate molecule do not find free active sites, this state is called saturation of active sites and the reactions rate does not increase.

Q18. What are substrates?

Ans. In enzymatic reactions, the molecules at which enzyme act are called substrate.

Q19. What is Prosthetic Group?

Ans. If organic cofactors are tightly bound to enzyme, they are called prosthetic group.

Q20. Describe induced fit model.

Ans. The induced fit model is more acceptable than lock and key model. In 1958, an American biologist Daniel Koshland suggested a modification to the lock and key model and proposed the induced fit model. According to this model the active sites are not rigid structures rather are molded into the required shape to perform its function.

Q21. What is optimum temperature for human enzymes?

Ans. The optimum temperature for the maximum working speed of human enzymes is 37^oC.

Q22. How do enzymes lower the activation energy?

Ans. Enzymes lower the activation energy in several ways. They do so by:

1. Altering the shape of the substrates and reducing the amount of energy required to complete the transition.
2. Disrupting the charge distribution on substrates.
3. Bringing substrates in the correct orientation to react.

Q23. Define protease. Ans. Proteases is an enzyme which breaks peptide bonds in protein.

Q24. What is the main use of enzymes in paper industry?

Ans. Enzymes break starch to lower its viscosity that aids in making paper.

Q25. Differentiate between intra-cellular and extra-cellular enzymes.

Ans. Enzymes can be categorized on the basis of the site where they work i.e. they may be:

1. Intra-cellular enzymes: Enzymes of glycolysis in the cytoplasm.
2. Extra-cellular enzymes: Enzymes working in the stomach.

Q26.Describe the use of enzymes in paper and food industry.

Ans.

1. Enzymes are used in food industry. Enzymes that break starch into simple sugars are used in production of white bread, buns etc.
2. Enzymes are used in paper industry. Enzymes break starch to lower its viscosity that aids in making paper.

Q27. Are all biochemical catalysts proteins?

Ans. All biochemical catalysts are not proteins, for examples some RNA molecules also catalyze reactions.

Q28. Who first used the term enzyme?

Ans. In 1878, German physiologist Winhelm Kuhne first used the term enzyme.

Q29. Name only factors affecting the rate of enzyme action.

Ans. 1: Temperature  2: Substrate concentration  3: pH

Q30. How does temperature affect the rate of enzyme action?

Ans. Every enzyme works at its maximum rate at a specific temperature called as optimum temperature for that enzyme. When temperature rises to a certain limit, heat adds in activation energy and provides kinetic energy and so reactions are accelerated.

Q31. Explain metabolism.

Ans. The term metabolism is derived from Greek word meaning "Change". The concept of metabolism was first of all given by Ibn-e-Nafees who stated that "the body and its parts are always undergoing change.

Q32.Write down the characteristics of enzymes.

Ans. Characteristics of enzymes:

1. Almost all enzymes are proteins
2. Enzymes speed up the reactions
3. Enzymes are not consumed by the reactions
4. Enzymes are usually very specific for the type of reactions and for the nature of their substrate

Q33. What is the effect of pH on the rate of enzyme action?

Ans. All enzymes work at their maximum rate at a narrow range of pH, called as the optimum pH. A slight change in this pH causes retardation in enzyme activity or blocks it completely. Change in pH can affect the ionization of the amino acids at the active sites. e.g. pepsin (working in stomach) is active in acidic medium (low pH).

Q34. Write down name of two enzymes.

Ans. i. Pepsin ii. Amylase

Q35. What do you mean by specificity of enzymes?

Ans. Enzymes are usually very specific for the type of reaction and for the nature of their substrates. The enzyme protease (which breaks peptide bonds in proteins) will not work on starch (which is broken down by an enzyme amylase). Similarly lipase enzyme acts only on lipids and digests them into fatty acids and glycerol.