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 needed to get a reaction started. It is the minimum amount of energy required for a chemical reaction to occur. This energy is needed to break the bonds in the reactant molecules and initiate the formation of new bonds in the product molecules. Activation energy acts as a barrier that must be overcome for a reaction to proceed. Once the activation energy is surpassed, the reaction can proceed on its own.
2.
Which of the following statements about enzymes is NOT true?
Correct Answer
B. All enzymes have the same shaps as their substrates
Explanation
Enzymes work best at a specified pH because their activity is influenced by the pH level of their environment. Enzymes are proteins and their shape is crucial for their function. The shape of an enzyme allows it to bind with its specific substrate and catalyze a chemical reaction. However, not all enzymes have the same shape as their substrates. Enzymes have a specific active site that is complementary in shape to their substrate, allowing for a precise fit and efficient catalysis. Therefore, the statement "All enzymes have the same shapes as their substrates" is not true.
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 speed up 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 reactions. Not all catalysts are enzymes, as enzymes are a specific type of catalyst found in biological systems. 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 catalyst is a substance that speeds up the rate of a chemical reaction without being consumed in the process. It works by providing an alternative pathway for the reaction to occur, lowering the activation energy required for the reaction to take place. This allows the reaction to happen more quickly and efficiently.
5.
Enzymes affect the reactions in living cells by changing the
Correct Answer
B. Speed of the reaction
Explanation
Enzymes are biological catalysts that speed up chemical reactions in living cells. They do this by lowering the activation energy required for the reaction to occur, thus increasing the rate or speed of the reaction. Enzymes themselves are not consumed or altered during the reaction, allowing them to be reused. Therefore, the correct answer is that enzymes affect the speed of the reaction in living cells.
6.
Without enzymes, the chemical reactions in the body would
Correct Answer
D. Occur too slowly to support life processes
Explanation
Enzymes are biological catalysts that speed up chemical reactions in the body. Without enzymes, these reactions would occur at a much slower rate, making it difficult for essential life processes to take place. The absence of enzymes would hinder the body's ability to break down nutrients, produce energy, and carry out other vital functions necessary for survival. Therefore, the correct answer is that without enzymes, chemical reactions would occur too slowly to support 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
Based on the graph, it can be inferred that Reaction 3 probably occurred in the presence of a catalyst. This is because the presence of a catalyst lowers the activation energy required for a reaction to occur, resulting in a faster reaction rate. In the graph, Reaction 3 has a lower activation energy compared to Reaction 2, indicating that a catalyst may have been involved in Reaction 3.
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 the energy changes during reactions 2 and 3. The higher activation energy shown in the graph for reaction 2 indicates that more energy is required for this reaction to occur compared to reaction 3. This suggests that reaction 2 occurs at a faster rate than reaction 3. Therefore, the statement "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" is true.
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 used repeatedly 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?
Correct Answer
D. It decreases by a factor of 100
Explanation
When the pH in a stomach increases from 2 to 4, it means that the stomach becomes less acidic. The pH scale is logarithmic, meaning that each unit change represents a tenfold difference in acidity or alkalinity. Therefore, an increase in pH by 2 units corresponds to a decrease in hydrogen ion concentration by a factor of 100 (10^2).
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, and acidity is determined by the concentration of H+ ions. As the concentration of H+ ions increases, the concentration of OH- ions decreases, leading to a decrease in pH.
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 slightly changes the shape of the enzyme. This means that the active site of the enzyme is flexible and can adjust its shape to accommodate the substrate. As the substrate binds to the active site, the enzyme undergoes conformational changes to create a more precise fit, enhancing the catalytic activity. This model explains how enzymes can specifically recognize and bind to their substrates, allowing for efficient enzymatic reactions.
13.
How do enzymes speed up chemical reactions?
Correct Answer
A. By reducing activation energy
Explanation
Enzymes speed up chemical reactions by reducing activation energy. Activation energy is the minimum amount of energy required for a reaction to occur. Enzymes lower this energy barrier, allowing the reaction to proceed more quickly. They do this by binding to the reactant molecules and bringing them closer together, making it easier for them to collide and react. This reduces the amount of energy needed for the reaction to happen, resulting in a faster reaction rate.
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 where the enzyme and the substrate come together and form a temporary enzyme-substrate complex. The active site has a specific shape that allows it to bind with the substrate, similar to a lock and key mechanism. This binding is essential for the enzyme to catalyze the reaction and convert the substrate into the desired product. The specificity of the active site ensures that only the correct substrate can bind and be acted upon by the enzyme.
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 the shape and activity of enzymes, cofactors (coenzymes) are necessary for some enzymes to function properly, and enzyme inhibitors can regulate or inhibit 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 catalyze a chemical reaction. Enzymes have specific binding sites called active sites, where the substrate molecule fits into and undergoes a 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 biological catalysts that speed up chemical reactions in living organisms. One of their characteristics is that they are specific, meaning each enzyme has a specific substrate that it acts upon. Enzymes are also reusable, as they are not consumed or used up in the reactions they catalyze. Additionally, enzymes are not permanently changed during the reaction, meaning they can be used repeatedly. Therefore, all of the given answer choices accurately describe characteristics of enzymes.