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Monday, 2 March 2015

FSc Notes Biology Part 1 Chapter 3 Enzymes

             FSc Notes Biology Part 1 Chapter 3 Enzymes

Q 1. What is catalyst?
Ans. A substrate which in minute amounts promotes chemical change without itself being used up in the reaction.

Q 2. Where are the enzymes important in photosynthesis found in the green cells? 
Ans. These enzymes are found in chloroplasts.

Q 3. Do all the enzymes need a co-factor for their proper function?
Ans. No, some enzymes require a co-factor for their proper functioning.

Q 4. What is the inactive state of the enzyme pepsin known as ?
Ans. It is known as pepsinogen.

Q 5. How many types of inhibitor?
Ans. There are two types of inhibitors:
  • Irreversible
  • Reversible
Q 6. What is the optimum temperature for human enzyme?
Ans. It is 37C

Q 7. Define enzyme.
Ans. The enzyme us a proteinaceous compound that catalyses biochemical reactions.

Q 8. Write important characteristics of enzymes.
Ans. Enzymes have the following characteristics:
  • Globular proteins
  • Increase reaction rate
  • No effect on end product
  • Required in small amount
  • Specific in action
  • Sensitivity
  • Require a co-factor
  • Lower the activation energy
  • Inhibition
  • Pure form
  • May be damaging

Q 9. How do extreme changes in pH effect the enzyme activity?
Ans. Extreme changes in pH cause the bonds in the enzyme to break, resulting in the enzyme denaturation.

Q 10. How can the effect of reversible inhibitors be naturalized?
Ans. Their effect can be neutralized completely or partly by an increase in the concentration of the substrate.

Q 11. Name the scientist who proposed lock and key model in 1890 to account for substrate-enzyme interaction?
Ans. The name of the scientist is Emil Fischer.

Q 12. What is substrate?
Ans. Substrate is a substance on which enzyme acts.

Q 13. Name the definite regions of the active site of an enzyme?
Ans. The definite regions are the binding site and the catalytic state.

Q 14. Quote few examples of inhibitors of enzyme.
Ans. These are cyanides, antibodies, anti-metabolism and some drugs.

Q 15. What is co-enzyme?
Ans. It is an organic compound which combines with an enzyme and plays an important part in its catalytic reaction, without being consumed in the process.

Q 16. Write down the optimum pHs for th enzyme pepsin, enterokinase, salivary amylase, catalase and orginase.
Ans. The optimum pHs for these are 2, 5.5, 6.8, 7.6 and 9.7 respectively.

Q 17. How dose heat accelerate chemical reactions at high temperature.
Ans. Heat provides activation energy which serves to accelerate chemical reactions at high temperature.

Q 18. List two conditions that destroy enzymatic activity by disrupting bonds between the atoms in an enzyme?
Ans. These conditions may be extreme increase in temperature and extreme changes in pH.

Q 19. Define prosthetic group.
Ans.  Prosthetic group is the non-protein part of an enzyme which is covalently bonded to the protein.

Q 20. How do irreversible inhibitors check the reaction rate? 
Ans. The irreversible inhibitors check the reaction rate by occupying the active sites of the enzyme or by destroying their globular structure.

Q 21. How do the irreversible inhibitors occupy the active sites if the enzyme?
Ans. They occupy the active sites either by forming covalent bonds or by blocking the active sites physically.

Q 22. How do low and high temperatures respectively affect the enzyme activity?
Ans. Low temperature decreases while the high temperature increases the enzyme activity but within certain limits.

Q 23. What are inhibitors?
Ans.  An inhibitor is a chemical substance that can react with the enzyme but it is not transformed into products and thus blocks the active site temporarily or permanently.

Q 24. Who and when proposed induce Fit Model regarding substrate and enzyme interaction?
Ans. Koshland in 1959 proposed induce fit model regarding substrate and enzyme interaction.

Q 25. What sort of medium is required by an enzyme, for its activity?
Ans. Aqueous medium is required by an  enzyme, for its activity.

Q 26. Where are the enzymes involved in cellular respiration found in the living cells?
Ans. These enzymes are found in the mitochondria.

Q 27. What is the active site of an enzyme?
Ans. Active sites is the small portion of the enzyme to which is its catalytic activity restricted.

Q 28. Define co-factor?
Ans. Any non-protein molecule or ion that is required for the proper functioning of an enzyme is called co-factor. Co-factor can be permanently bound to the active site or ma bind loosely with the substrate during catalysis.

Q 29. Differentiate between apoenzyme and holoenzyme.
Ans. An enzyme whose co-factor has been removed, rendering i.e., catalytically machine is known as an apoenzyme. When apoenzyme is combined with is co-enzyme, it forms a holoenzyme.

Q 30. Would bio-chemical reaction not operate, if the lining body were without enzymes?
Ans. The bio-chemical reaction would operate but at such a slow speed that life would be impossible.

Q 31. List two conditions that destroy enzymatic activity by disrupting bonds between the atoms in an enzyme.
Ans. High temperature and high pH
Q 32. How do low and high temperature, respectively effect an enzyme activity?
Ans. Temperature and Enzyme Activity:  The rate of enzyme controlled reaction may increase with increase in temperature but up to certain limit. All enzymes can work at their specific temperature called as optimum temperature. For enzymes of human body 37C is the optimum temperature. Heat provides activation energy and therefore chemical reactions are accelerated at high temperature. Heat also supplies kinetic energy to the reacting molecules, causing them to move rapidly. Thus the reactants move more quickly and chances of their collision with each other are increased.However, further increase in heat energy also increases the vibrations of atoms which make up the enzyme molecule. If the vibrations become too violent, globular structure essential for enzyme activity is lost and the enzyme is said to be denatured.
Low Temperature: At low temperature kinetic energy become very low due to which enzyme activity cease.


Written By: Asad Hussain