1. What is the definition of metabolism?
All the chemical reactions that happens in the organism.
2 What are the two types of metabolism?
(1) catabolism (usually energy is released)
(2) anabolism (usually require energy)
3. To start a chemical reaction, what is the first criteria?
The reactants must absorb enough energy, called ‘activation energy’.
4. What are the roles of enzymes in metabolism?
It acts as a catalyst to lower the activation energy.
5. What are the characteristics of enzymes?
(1) It is a biological catalyst, It can lower the activation energy.
(this is in fact the function and not a characteristic)
(2) It is protein
- therefore it is affected by temperature and pH
(3) It is specific, its active site will only fit compatible substrate.
(4) It will not change after a reaction
- therefore it is reusable and
- only a small amount is enough
6. What is the name of the structure on the enzyme that the substrate fits on?
Active site. If this site is damage, we say the enzyme has lost its ability (denatured).
7. How can enzyme exert it effects (the mechanism of how enzyme works)?
(1) the active site of the enzyme binds to the substrate molecule(s)
(2) to form an enzyme substrate complex
(3) the product is formed, the enzyme is released.
Note: Product may be produced from the enzyme substrate complex, but the reaction may be reversed, forming the substrates.
8. What are the features of the ‘lock and key’ hypothesis?
Specificity
9. What is the name of the rate of enzymatic reaction?
enzyme activity
10. What are the factors that affect the rate of enzymatic reaction?
(1) temperature (has optimum temperature)
(2) pH value (has optimum pH)
(3) inhibitor (lowers the enzyme activity)
11. How does temperature affect the activity of enzymes (mechanism)?
(1) at low temperature, when the temperature increases, there are more kinetic energy in the enzyme molecules and the substrate molecules.
(2) the chance of collision between the enzyme and the substrate increase.
(3) the enzyme activity will become higher.
(4) until the optimum temperature is reached.
(5) above the optimum temperature, if the temperature continue to rise, the active site of certain enzyme will be damaged (denatured)
(6) enzyme activity will decrease
(7) until at a certain high temperature, all active sites are damaged
(8) by then, there will be no more enzyme activity.
12. At both low and high temperature, the enzyme activity will decrease. What is the difference?
At low temperature, the enzyme is not active, by as temperature increases, the activity will increase.
At high temperature, since all enzymes have denatured, and denaturation is irreversible, so even though the temperature is lowered, the enzyme activity will not increase.
13. How does pH value affect the activity of enzymes?
At optimum pH value, enzyme activity is highest. In other unsuitable pH, the enzyme will denature.
Note: An enzyme is a 3D protein structure, hold together by certain chemical bondings, which is affected by charged. Different pH has different charges, so different enzyme will be affected by different pH.
14. What is the industrial use of enzymes?
(1) biological washing powder
(2) stonewashed jeans
(3) contact lens cleaners
(4) meat tenderisers
(5) cheese
(6) fruit juice
15. What are the advantages of using enzymes in industries?
(1) shorten the production time (since the reaction of enzymes can be sped up)
(2) reduce the production of unwanted products (since enzymes are specific in action)
(3) lowers the cost of production (since enzymes are reusable)
(4) Can reduce the cost required for providing extreme conditions (since most enzymes can work at moderate conditions)
16. What are the limitation of application of enzymes in industries?
(1) enzymes are sensitive to pH and temperature
(2) they are easily affected by inhibitors.
17. What are the two types of inhibitors?
(1) competitive inhibitors
(2) non-competitive inhibitors
Note: Either one will affect the active site and lower the enzyme activity.
18. What is the competitive inhibitor competing with the enzyme for?
The active site. So that the enzyme cannot bind to the substrate. But if the substrate increase to a certain level, the enzyme activity will resume to its original level.
19. How does non-competitive inhibitors affect enzyme activity?
Non-competitive inhibitors combines with the enzymes at other sites, causing the active site to change shape so that the substrate cannot combine with the active site. In this case, an increase in inhibitor concentration have no effect in increasing enzyme activity.
20. How can we differentiate biological catalysts and chemical catalysts?
For biological catalysts, there is an optimum temperature. If the optimum temperature is exceeded, the reaction will be lowered.
For chemical catalysts, there is no optimum temperature. The higher the temperature, the faster the reaction.