Q.1 Cellular respiration is an exothermic reaction and photosynthesis is an endothermic reaction. How does the required activation energy compare for these two reactions?

1. Cellular respiration needs a smaller amount of energy to activate the reaction because the products are at a lower energy state than the reactants.
2. Photosynthesis needs a higher amount of energy to activate the reaction because the products are at a lower energy state than the reactants.
3. Photosynthesis needs a smaller amount of energy to activate the reaction because the products are at a lower energy state than the reactants.
4. Cellular respiration needs a higher amount of energy to activate the reaction because the products are at a lower energy state than the reactants.

Q.2 How do enzymes affect chemical reactions?
1.They lower activation energy.
2.They provide activation energy.
3.They increase activation energy.
4.They eliminate activation energy.

Q.3 Which lists the correct order of steps involved in the formation of an enzyme-substrate complex?
1.enzyme-substrate complex forms > enzyme binds to substrate at active site > chemical reaction takes place > products are released
2.enzyme binds to substrate at active site > enzyme-substrate complex forms > chemical reaction takes
3.chemical reaction takes place > products are released > enzyme binds to substrate at active site > enzyme-substrate complex forms
4.enzyme binds to substrate at active site > chemical reaction takes place > products are released > enzyme-substrate complex forms