IGCSE Biology Paper-2: Specimen Questions with Answers 186 - 187 of 203
Question 186
Question
MCQ▾The diagram shows an animal whose scientific name is Falco peregrinus.
To which class does it belong?
Choices
| Choice (4) | |
|---|---|
a. | Aves |
b. | Reptiles |
c. | Amphibians |
d. | Mammals |
Answer
a.Explanation
Question 187
Question
MCQ▾Many enzymes do not work at temperatures above .
Which statement gives best explanation of this?
Choices
| Choice (4) | |
|---|---|
a. | Product molecules are not made because the active site has changed shape. |
b. | Substrate molecules lost their structure. |
c. | Product molecules change shape so they do not fit the active site. |
d. | Substrate molecules are not available at high temperature. |
Answer
a.Explanation
Temperature
- Enzyme functions optimally at certain temperature. As the temperature increases the kinetic energy also increases, molecules move faster and it increases the chance of substrate colliding the enzyme՚s active site and binding followed by reaction.
- However, if the temperature is too high, the enzyme protein denatures (cools) , thereby destroying the shape of active binding site (cannot bind to the substrate anymore) and decreasing the enzyme reaction rate.
