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 ..
A.1 The correct answer is:
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.
Cellular respiration is the process by which cells convert glucose and oxygen into carbon dioxide, water, and ATP (energy). It is an exothermic reaction because energy is released in the form of ATP. The products of cellular respiration (carbon dioxide and water) have a lower energy state than the reactants (glucose and oxygen). Therefore, in order for the reaction to proceed, a higher amount of activation energy is needed to reach the transition state where the reactants can be converted into products.
To understand this concept, you can think of a hill. The reactants are at the bottom of the hill (lower energy state) and the products are at the top of the hill (higher energy state). In order to reach the top of the hill and form the products, a higher amount of energy (activation energy) is required.
A.2 The correct answer is:
1. They lower activation energy.
Enzymes are catalysts that speed up chemical reactions by lowering the activation energy needed to start the reaction. Activation energy is the energy required for a chemical reaction to occur. Enzymes achieve this by providing an alternative pathway for the reaction, with a lower activation energy. By lowering the activation energy, enzymes increase the rate at which reactions occur, without being consumed or permanently altered in the process.
Enzymes are generally proteins that have a specific shape and active site. The active site is a specific region of the enzyme that binds to the substrate (reactant) molecule. When the substrate binds to the enzyme's active site, it forms an enzyme-substrate complex. This complex undergoes a chemical reaction, resulting in the formation of products. Enzymes can be used over and over again as they are not consumed in the reaction.
A.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 correct order of steps involved in the formation of an enzyme-substrate complex is as follows:
1. The enzyme binds to the substrate at its active site. The active site is a specific region on the enzyme where the substrate molecules can bind. The binding of the substrate to the active site forms the enzyme-substrate complex.
2. Once the enzyme-substrate complex is formed, a chemical reaction takes place. The enzyme facilitates the conversion of the substrate into products by lowering the activation energy required for the reaction to occur. This reaction can involve breaking or forming chemical bonds.
3. After the reaction takes place, the products are released from the active site of the enzyme. The enzyme is then free to bind to another substrate molecule and catalyze another reaction.
Overall, enzymes play a crucial role in biological systems by increasing the rate of chemical reactions and allowing them to occur under mild conditions within cells.