1.
What is the term used to describe the energy needed to get a reaction started?
Correct Answer
B. Activation energy
Explanation
Activation energy is the term used to describe the energy required to initiate a chemical reaction. It represents the energy barrier that must be overcome for reactant molecules to transform into products. This energy is needed to break the existing bonds in the reactant molecules and start the formation of new bonds in the product molecules. Activation energy determines the rate at which a reaction occurs and is influenced by factors such as temperature, concentration, and catalysts.
2.
Which of the following statements about enzymes is NOT true?
a.
Enzymes work best at a specified pH.
b.
All enzymes have the same shape as their substrates.
c.
Enzymes are proteins.
d.
The shape of an enzyme allows it to do its job.
Correct Answer
B. All enzymes have the same shaps as their substrates
Explanation
The statement "All enzymes have the same shape as their substrates" is not true. Enzymes have a specific three-dimensional shape, known as their tertiary structure, which allows them to bind to their substrates and catalyze chemical reactions. The shape of the enzyme's active site is complementary to the shape of its substrate, allowing for a specific and precise interaction. However, the shape of the enzyme itself is not the same as its substrate.
3.
Which of the following statements is true about catalysts?
a.
Catalysts slow down the rate of chemical reactions.
b.
All catalysts are enzymes.
c.
Catalysts are used up during a chemical reaction.
d.
Catalysts lower the activation energy of a chemical reaction.
Correct Answer
D. Catalysts lower the activation energy of a chemical reaction
Explanation
Catalysts are substances that increase the rate of a chemical reaction by lowering the activation energy required for the reaction to occur. They do not slow down the rate of chemical reactions. Not all catalysts are enzymes, as enzymes are a specific type of catalyst found in living organisms. Catalysts are not used up during a chemical reaction, as they are not consumed in the reaction and can be reused. Therefore, the correct statement is that catalysts lower the activation energy of a chemical reaction.
4.
A substance that accelerates the rate of a chemical reaction is called a(an)
Correct Answer
A. Catalyst
Explanation
A substance that accelerates the rate of a chemical reaction is called a catalyst. A catalyst works by providing an alternative reaction pathway with a lower activation energy, allowing the reaction to occur more quickly. It does not get consumed in the reaction and can be used repeatedly. Lipids, molecules, and proteins are not specifically known for their ability to accelerate chemical reactions.
5.
Enzymes affect the reactions in living cells by changing the
Correct Answer
B. Speed of the reaction
Explanation
Enzymes act as catalysts in living cells, meaning they speed up chemical reactions without being consumed in the process. They achieve this by lowering the activation energy required for the reaction to occur. Therefore, enzymes directly affect the speed of the reaction, allowing it to occur more rapidly than it would without the enzyme. The other options, such as changing the products, temperature, or pH of the reaction, may indirectly influence the reaction speed but are not the primary role of enzymes in affecting reactions.
6.
Without enzymes, the chemical reactions in the body would
a.
happen too fast.
b.
occur at much the same rate as they do with enzymes.
c.
require a different pH.
d.
occur too slowly to support life processes.
Correct Answer
D. Occur too slowly to support life processes
Explanation
Without enzymes, the chemical reactions in the body would occur too slowly to support life processes. Enzymes act as catalysts, speeding up the rate of chemical reactions in the body. They lower the activation energy required for a reaction to occur, allowing it to happen more quickly. Without enzymes, the reactions would proceed at a much slower rate, which would not be sufficient to sustain the necessary life processes.
7.
Refer to the graph above. Reaction 3 in the graph
Correct Answer
A. Probably occurred in the presence of a catalyst
Explanation
The graph suggests that reaction 3 occurred in the presence of a catalyst because it has a lower activation energy compared to reaction 2. A catalyst lowers the activation energy required for a reaction to occur, making it faster. The graph shows that reaction 3 has a lower activation energy than reaction 2, indicating that a catalyst was likely present.
8.
Refer to the graph above. Which of these statements regarding the graph is true?
Correct Answer
B.
The difference in the grapHs shown for reaction 2 and reaction 3 is due to a difference in the activation energy needed for these two reactions.
Explanation
The graph shows that reaction 2 has a higher activation energy barrier compared to reaction 3. This means that more energy is required for reaction 2 to proceed, resulting in a slower reaction rate. Therefore, the statement that "Reaction 2 occurs faster than reaction 3 because reaction 2 requires more energy than reaction 3" is incorrect. Instead, the correct statement is that the difference in the graphs is due to a difference in the activation energy needed for the two reactions.
9.
Two students conduct an experiment in which they measure the concentration of an enzyme in a test tube at 1 minute intervals over the course of an enxymatic reaction. Each of the students makes a prediction about what will happen to the enzyme concentration as the reaction progresses.
Student 1 predicts that the concentration of the enzyme in the test tube will decrease as the reaction progresses.
Student 2 predicts that the concentration of the enzyme in the test tube will stay the same as the reaction progresses.
Which student’s prediction is correct, and why?
Correct Answer
D. Student 2; enzymes are not depleted as a reaction progresses
Explanation
Student 2's prediction is correct because enzymes are not depleted as a reaction progresses. Enzymes are catalysts that facilitate chemical reactions without being consumed in the process. They can be reused multiple times and remain unchanged at the end of the reaction. Therefore, the concentration of the enzyme in the test tube will stay the same as the reaction progresses.
10.
When the pH in a stomach increases from 2 to 4, how does the hydrogen ion concentration change?
a.
It increases by a factor of 2.
b.
It increases by a factor of 100.
c.
It decreases by a factor of 2.
d.
It decreases by a factor of 100.
Correct Answer
D. It decreases by a factor of 100
Explanation
When the pH in a stomach increases from 2 to 4, the hydrogen ion concentration decreases by a factor of 100. This is because pH is a measure of the concentration of hydrogen ions in a solution. As the pH increases, it indicates a decrease in the concentration of hydrogen ions. In this case, the increase in pH from 2 to 4 represents a decrease in the concentration of hydrogen ions by 100 times.
11.
When the pH in a stomach decreases, what is happening?
Correct Answer
E. H+ ions are increasing & OH- ions are decreasing.
Explanation
When the pH in a stomach decreases, it means that the concentration of hydrogen ions (H+) is increasing. At the same time, the concentration of hydroxide ions (OH-) is decreasing. This is because a decrease in pH indicates an increase in acidity, which is caused by an increase in the concentration of H+ ions. The decrease in OH- ions is a result of the increase in H+ ions, as they combine to form water (H2O). Therefore, the correct answer is that H+ ions are increasing and OH- ions are decreasing.
12.
Which statement most accurately describes the induced fit model of enzyme function?
Correct Answer
C. Substrate binding slightly changes the shape of the enzyme
Explanation
The induced fit model of enzyme function suggests that substrate binding causes a slight change in the shape of the enzyme. This change allows for a better fit between the enzyme and the substrate, enhancing the efficiency of the catalytic reaction. This model emphasizes the dynamic nature of enzyme-substrate interactions, where the active site is not rigid but can adapt to accommodate the substrate. This flexibility ensures that the enzyme can effectively bind to and catalyze the reaction with the substrate.
13.
How do enzymes speed up chemical reactions?
Correct Answer
A. By reducing activation energy
Explanation
Enzymes speed up chemical reactions by reducing the activation energy required for the reaction to occur. Activation energy is the energy needed to initiate a chemical reaction. By lowering this energy barrier, enzymes allow reactions to happen more easily and quickly. They do this by binding to the reactant molecules and bringing them closer together, facilitating the formation of new bonds and the breaking of existing ones. This lowers the energy required for the reaction to proceed, making it more efficient.
14.
The active site of an enzyme is
Correct Answer
A. Where the reactant fits into the enzyme
Explanation
The active site of an enzyme is where the reactant fits into the enzyme. This is because enzymes are proteins that catalyze chemical reactions by binding to specific substrates at their active sites. The active site has a specific shape that allows it to bind with the reactant, forming an enzyme-substrate complex. This binding is essential for the enzyme to catalyze the reaction and facilitate the conversion of the reactant into the desired product. The specificity of the active site's shape ensures that enzymes can selectively bind to their specific substrates and carry out their biological functions effectively.
15.
Which of the following factors affects enzyme activity?
Correct Answer
D. All of the answer choices are correct
Explanation
All of the answer choices are correct because environmental factors such as temperature and pH can affect enzyme activity by altering the enzyme's shape and ability to bind to substrates. Cofactors, such as vitamins or metal ions, are necessary for some enzymes to function properly. Enzyme inhibitors can also affect enzyme activity by binding to the enzyme and preventing it from carrying out its normal function. Therefore, all of these factors can have an impact on enzyme activity.
16.
Which of the following is the best definition for a substrate?
Correct Answer
A. A reactant that an enzyme binds with to carry out a reaction
Explanation
A substrate is defined as a reactant that binds with an enzyme in order to facilitate and carry out a reaction. Enzymes have specific active sites where substrates bind, allowing the enzyme to catalyze the reaction. Therefore, the best definition for a substrate is a reactant that an enzyme binds with to carry out a reaction.
17.
Which of the following is a characteristic of an enzyme?
Correct Answer
D. All of the answer choices are correct
Explanation
Enzymes are catalysts that speed up chemical reactions in the body. One of their characteristics is that they are specific, meaning they can only catalyze a particular reaction. They are also reusable, as they can be used over and over again in multiple reactions. Additionally, enzymes are not permanently changed during the reaction, meaning they can be used again for other reactions. Therefore, all of the given answer choices are correct in describing the characteristics of an enzyme.