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
Q.1 The correct answer is: 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.
To understand why cellular respiration requires less activation energy compared to photosynthesis, it's helpful to first understand the energy changes involved in these processes.
Cellular respiration is a metabolic process that takes place in the cells of organisms to produce energy in the form of ATP (adenosine triphosphate). It involves the breakdown of glucose and other organic molecules in the presence of oxygen. The chemical reaction releases energy, and the products (carbon dioxide and water) are at a lower energy state than the reactants (glucose and oxygen).
On the other hand, photosynthesis is the process by which plants, algae, and some bacteria convert sunlight energy into chemical energy in the form of glucose. It involves the absorption of light by chlorophyll and the conversion of carbon dioxide and water into glucose and oxygen. Unlike cellular respiration, photosynthesis is an endothermic process, meaning it requires an input of energy (in the form of sunlight) to proceed.
Activation energy is the energy required to initiate a chemical reaction and reach the transition state, where the reactants can form products. In the case of cellular respiration, the reactants (glucose and oxygen) have a higher energy than the products (carbon dioxide and water). Since the reactants are already at a higher energy state, less additional energy is needed to reach the transition state and initiate the reaction. Therefore, cellular respiration requires a smaller amount of activation energy.
Q.2 The correct answer is: 1.They lower activation energy.
Enzymes are biological catalysts that speed up chemical reactions in living organisms. They facilitate and enhance the rates of reactions by lowering the activation energy required for the reaction to occur.
Activation energy is the minimum amount of energy required for a chemical reaction to occur. It represents the energy barrier that reactant molecules must overcome to reach the transition state, where bonds can break and new bonds can form.
Enzymes work by binding to specific reactant molecules called substrates at their active sites. The active site is a region on the enzyme's surface that has a complementary shape to the substrate. This binding brings the reactants (substrates) close together and allows them to interact more effectively, facilitating the formation of product molecules.
Furthermore, enzymes can also stabilize the transition state of a reaction by providing an alternative reaction pathway that requires less energy to proceed. This alternative pathway lowers the overall activation energy, making it easier for the reaction to occur. However, enzymes themselves are not consumed or permanently altered during the reaction process and can be reused for multiple reactions.
Q.3 The correct answer is: 2. enzyme binds to substrate at active site > enzyme-substrate complex forms > chemical reaction takes place > products are released
The formation of an enzyme-substrate complex involves several steps, which occur in a specific order.
1. The enzyme binds to the substrate at its active site: The active site is a region on the enzyme's surface that is complementary in shape to the substrate molecule. This binding occurs due to the specific recognition between the enzyme and substrate, based on their respective chemical structures.
2. Enzyme-substrate complex forms: Once the enzyme and substrate are bound together, they form a temporary complex called the enzyme-substrate complex. This complex allows for specific interactions between the enzyme and substrate, which facilitate the chemical reaction.
3. Chemical reaction takes place: The enzyme catalyzes the reaction by lowering the activation energy required for the conversion of the substrate into the product(s). It provides an environment that brings the reactants together and enables them to interact more effectively, leading to the formation of the desired product(s).
4. Products are released: After the chemical reaction is completed, the products are released from the active site of the enzyme. The enzyme is then free to bind other substrate molecules and repeat the process, as it is not consumed or permanently altered during the reaction.
So, the correct order of steps involved in the formation of an enzyme-substrate complex is: 2. enzyme binds to substrate at active site > enzyme-substrate complex forms > chemical reaction takes place > products are released.