Unit 1 Chapter 3 (1st Secondary) Biology

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The enzyme catalase catalyzes the reaction that breaks down hydrogen peroxide into water and oxygen. The graph shows how much oxygen is produced over time when this reaction occurs with and without catalase. Which of the following statements correctly describes the trend shown?
- The reaction produces more oxygen when catalase is present.
- The reaction produces more oxygen when catalase is not present.
- The reaction produces oxygen at a quicker rate when catalase is present.
- The reaction produces oxygen at a quicker rate when catalase is not present.

About This Quiz

This quiz assesses understanding of enzyme activity, focusing on factors like temperature and pH, and their effects on enzymes such as pepsin and trypsin.

Unit 1 Chapter 3 (1st Secondary) Biology - Quiz

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2.

In the reaction involving the catalase enzyme and the hydrogen peroxide, the enzyme breaks the reactant into …….
- H₂O and O₂
- H⁺ and O₂
- H₂O₂ + H₂
- None of the above
Correct Answer

A. H₂O and O₂

Explanation

The catalase enzyme catalyzes the decomposition of hydrogen peroxide (H2O2) into water (H2O) and oxygen gas (O2). This reaction occurs naturally in cells and helps to break down the toxic hydrogen peroxide into harmless water and oxygen.

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3.

The graph below illustrates the free energy of a biochemical reaction, once in the absence of an enzyme and another time in the presence of a specific enzyme. In the presence of the enzyme, the energy of activation of the reaction is lowered from ………. to ……..
- (D A) / (A C)
- (B A) / (A C)
- (D A) / (B A)
- (B A) / (B C)
Correct Answer

A. (D A) / (B A)

Explanation

In the presence of the enzyme, the energy of activation of the reaction is lowered from (D A) to (B A). This means that the enzyme helps to decrease the amount of energy required for the reaction to occur, making it easier for the reaction to proceed. The ratio (D A) / (B A) represents the decrease in energy of activation achieved by the enzyme.

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4.

Oxidation of glucose during cellular respiration is considered a process of …..
- Catabolism
- Anabolism
- Excretion
- Digestion
Correct Answer

A. Catabolism

Explanation

The oxidation of glucose during cellular respiration is a catabolic process. Catabolism refers to the breakdown of complex molecules into simpler ones, releasing energy in the process. Glucose is broken down into smaller molecules such as carbon dioxide and water, and energy is released in the form of ATP. This process is essential for the production of energy in cells. Anabolism, on the other hand, is the process of building complex molecules from simpler ones, which is not the case during the oxidation of glucose. Excretion and digestion are unrelated processes to the oxidation of glucose.

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1
5.

Enzymes are characterized than other chemical catalysts in that they …….
- Increase the activation energy.
- Are specific for a certain substrate.
- Participate in the chemical reaction.
- Slow down the rate of the chemical reaction.
Correct Answer

A. Are specific for a certain substrate.

Explanation

Enzymes are characterized by their specificity for a certain substrate, meaning that they are designed to bind and interact with a particular molecule or group of molecules. This specificity allows enzymes to catalyze specific chemical reactions, as they have a unique shape and active site that can accommodate the substrate and facilitate the reaction. Unlike other chemical catalysts, enzymes do not increase the activation energy or slow down the rate of the chemical reaction. They actively participate in the reaction by lowering the activation energy and increasing the rate of the reaction.

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6.

The graph provided shows the reaction profile of a biological reaction. Which letter indicates the activation energy?
- X
- Y
- Z
- W
Correct Answer

A. X

Explanation

The activation energy is the energy required for a reaction to occur. In the given graph, the letter X represents the highest point on the reaction profile, which indicates the activation energy. This is because the reactants need to overcome this energy barrier in order to proceed to the products.

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7.

Why does the graph level-off at point (B) if you know that the reaction is done at constant temperature and pH ?
- Because the enzyme is beginning to denature.
- Because the enzyme has been used up.
- Because there are not enough substrate molecules left.
- Because of the change in the power of hydrogen.
Correct Answer

A. Because there are not enough substrate molecules left.

Explanation

The graph levels off at point (B) because there are not enough substrate molecules left. At the beginning of the reaction, the substrate concentration is high, and the reaction rate increases as more substrate molecules collide with the enzyme. However, as the reaction progresses, the substrate molecules are converted into product, leading to a decrease in substrate concentration. Eventually, the substrate concentration becomes limiting, causing the reaction rate to level off. This is known as substrate depletion, and it explains why the graph levels off at point (B).

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8.

If in a certain enzymatic reaction, an enzyme (E) works on a substrate (S). What makes the rate of reaction constant after some time of starting the reaction?
- The increase in the enzyme concentration
- The increase in the substrate concentration
- The saturation of the enzyme active sites in all enzyme molecules
- The increase in the number of active sites
Correct Answer

A. The saturation of the enzyme active sites in all enzyme molecules

Explanation

The rate of reaction becomes constant after some time of starting the reaction because the enzyme active sites become saturated. This means that all the active sites on the enzyme molecules are occupied by substrate molecules, and no more substrate molecules can bind to the enzyme. As a result, the rate of reaction reaches a maximum and remains constant as long as the concentration of substrate and enzyme remains constant. Increasing the concentration of enzyme or substrate may initially increase the rate of reaction, but once the active sites are saturated, further increases in concentration will not affect the rate.

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9.

Enzyme catalyzing rearrangement of atomic groupings without altering molecular weight or number of atoms is ……
- Ligase
- Isomerase
- Lipase
- Pepsin
Correct Answer

A. Isomerase

Explanation

Isomerases are enzymes that catalyze the rearrangement of atomic groupings within a molecule, resulting in the formation of isomers. Isomers are molecules that have the same molecular formula but different structural arrangements. In this case, the enzyme catalyzes the rearrangement of atomic groupings without altering the molecular weight or number of atoms in the molecule. Ligase, lipase, and pepsin do not perform this specific function, making isomerase the correct answer.

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10.

When you eat a large meal, the _____ activity called digestion takes the biomolecules you consumed and breaks them down into smaller molecules.
- Nutrition
- Anabolic
- Catabolic
- Respiratory
Correct Answer

A. Catabolic

Explanation

When you eat a large meal, the catabolic activity called digestion takes the biomolecules you consumed and breaks them down into smaller molecules. Catabolic refers to the process of breaking down complex molecules into simpler ones, which is exactly what happens during digestion. This process allows the body to extract and absorb nutrients from the food we eat.

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1
11.

The relationship between an enzyme and a reactant molecule can best be described as ……….
- A temporary association.
- An association stabilized by a covalent bond.
- One in which the enzyme is changed permanently.
- A permanent mutual alteration of structure.
- Non-complementary binding.
Correct Answer

A. A temporary association.

Explanation

Enzymes and reactant molecules form a temporary association because enzymes catalyze reactions by binding to the reactant molecules, forming an enzyme-substrate complex. This association is temporary because once the reaction is complete, the enzyme releases the product and can bind to another substrate molecule. This allows the enzyme to be reused and participate in multiple reactions.

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12.

According to the figure below, Which of the following statements is incorrect ......
- Photosynthesis process requires energy.
- Oxidation of free fatty acids requires energy.
- Adding an amino acid to a polypeptide chain requires energy.
- All condensation reactions are anabolic.
Correct Answer

A. Oxidation of free fatty acids requires energy.

Explanation

The oxidation of free fatty acids actually releases energy, rather than requiring it. During this process, the fatty acids are broken down to produce ATP, which is a source of energy for the body. This is why the statement is incorrect.

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13.

Which of the following statements is true about metabolism?
- It only involves the processes that build up the large molecules in the body.
- It only involves the processes that break down the small molecules in the body.
- It only involves the processes that break down the large molecules in the body.
- It involves all of the processes that break down and build up molecules in the body.
Correct Answer

A. It involves all of the processes that break down and build up molecules in the body.

Explanation

Metabolism involves all of the processes that break down and build up molecules in the body. This includes both anabolic processes, which build up larger molecules from smaller ones, and catabolic processes, which break down larger molecules into smaller ones. Therefore, the statement that metabolism involves all of the processes that break down and build up molecules in the body is true.

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14.

In some metabolic reactions, large molecules are broken down into smaller ones. What biological reaction breaks down glucose in cells to release energy?
- Mitosis
- Respiration
- Osmosis
- Photosynthesis
Correct Answer

A. Respiration

Explanation

Respiration is the biological reaction that breaks down glucose in cells to release energy. During respiration, glucose is broken down in a series of chemical reactions, ultimately producing ATP (adenosine triphosphate), which is the main energy currency of cells. This process occurs in the mitochondria of cells and is essential for providing energy for various cellular activities. Mitosis is the process of cell division, osmosis is the movement of water across a semipermeable membrane, and photosynthesis is the process by which plants convert sunlight into energy.

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15.

In enzymatic reactions, substrates (reactants) and products have specific energies. In order to transform the reactants into products, the reactants would have to go through a transition state which is usually higher in energy (point B in the graph). To get to this transition state, the system requires activation energy. (The energy required to start a reaction) The lower the activation energy, the faster the reaction happens. The graph below illustrates an enzymatic reaction, where the activation energy of this reaction, is the difference between the two points ........
- (A) and (D)
- (B) and (D)
- (C) and (D)
- (B) and (A)
Correct Answer

A. (B) and (A)

Explanation

The graph illustrates an enzymatic reaction, with the transition state represented by point B. The activation energy required to reach this transition state is the difference between points B and A. Therefore, the correct answer is (B) and (A).

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16.

Which is not true about enzymes?
- Enzymes are biological catalysts.
- Enzymes are proteins.
- Enzymes speed up reactions by raising the activation energy required to start the reaction.
- Enzymes are not changed in the reaction.
Correct Answer

A. Enzymes speed up reactions by raising the activation energy required to start the reaction.

Explanation

Enzymes actually lower the activation energy required to start a reaction, not raise it. This allows reactions to occur more easily and at a faster rate.

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17.

Assuming that rolling a huge ball across a hill as in the figure below, represents a biochemical reaction that takes place without enzyme. So the energy of activation can be illustrated by ……..
- (A)
- (B)
- (A) plus (B)
- (A) minus (B)
Correct Answer

A. (A)

Explanation

The correct answer is (A) because the energy of activation represents the energy barrier that must be overcome for a biochemical reaction to occur. Rolling a huge ball across a hill without an enzyme represents a reaction without any assistance, so the energy of activation can be illustrated by the energy required to push the ball up the hill.

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18.

“Lock and key theory” is related with …....
- Digestion of carbohydrates in the intestine.
- Absorption of carbohydrates from intestine.
- Absorption of proteins to the blood.
- Diffusion of water to inside plant cells.
Correct Answer

A. Digestion of carbohydrates in the intestine.

Explanation

The lock and key theory is related to the digestion of carbohydrates in the intestine. This theory suggests that enzymes, which act as the "keys," have specific shapes that fit into the "locks" of specific substrates. In the case of carbohydrate digestion, enzymes such as amylase break down complex carbohydrates into smaller molecules that can be absorbed and utilized by the body. This process of breaking down carbohydrates into simpler forms is essential for their digestion and absorption in the intestine.

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19.

Why is a period of intense exercise often followed by heavy breathing?
- To increase the temperature of the body
- To increase the heart rate
- To remove oxygen from the bloodstream
- To provide cells with energy
- To replace the oxygen lost
Correct Answer

A. To replace the oxygen lost

Explanation

During intense exercise, the body requires more oxygen to meet the increased energy demands. As a result, the breathing rate increases to take in more oxygen and remove carbon dioxide. This heavy breathing is necessary to replace the oxygen that is being used up by the muscles during exercise.

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20.

Look at the following diagram, which represents the energy diagram for a chemical reaction. Which point on the diagram represents the point at which the transition state exists?
- A
- B
- C
- D
Correct Answer

A. B

Explanation

In the given energy diagram, the transition state represents the highest energy point in the reaction pathway. It is the point at which the reactants have absorbed enough energy to overcome the activation energy barrier and form the products. Looking at the diagram, point B is the highest point, indicating that it represents the transition state.

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21.

Which of the following statements correctly links enzymes, substrates, and active sites?
- The enzyme’s active site is constantly changing to have a complementary shape to a range of substrates.
- The substrate has an active site that has a complementary shape to a range of enzymes.
- The substrate has an active site that has an identical shape to a specific enzyme.
- The enzyme has an active site that has an identical shape to a range of substrates.
- The enzyme has an active site that has a complementary shape to a specific substrate.
Correct Answer

A. The enzyme has an active site that has a complementary shape to a specific substrate.

Explanation

The correct answer is "The enzyme has an active site that has a complementary shape to a specific substrate." This statement accurately describes the relationship between enzymes, substrates, and active sites. Enzymes are proteins that catalyze chemical reactions by binding to specific substrates at their active sites. The active site of an enzyme is specifically shaped to fit and bind with a particular substrate, like a lock and key. This complementary shape allows the enzyme to interact with the substrate and facilitate the reaction.

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22.

In humans salivary amylase enzyme breaks down starch. What is the optimum pH for this reaction?
- 7.8 - 8.2
- 2.5 - 3
- 5.7 - 6
- 6.8 - 7.5
Correct Answer

A. 6.8 - 7.5

Explanation

Salivary amylase is an enzyme that helps break down starch in the mouth. Enzymes usually have an optimum pH at which they function most effectively. In the case of salivary amylase, the optimum pH range for its activity is 6.8 - 7.5. This means that the enzyme works best and catalyzes the breakdown of starch most efficiently within this pH range. Deviations from this pH range can result in reduced enzyme activity and slower starch digestion.

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23.

In the reaction involving the catalase and the hydrogen peroxide, at the beginning time, the …..
- Number of reactant break down decreases
- Number of reactant break down increases
- Reactants break down decreases first then increases
- None of them
Correct Answer

A. Number of reactant break down increases

Explanation

In the reaction involving catalase and hydrogen peroxide, the catalase enzyme helps break down the hydrogen peroxide into water and oxygen. At the beginning of the reaction, there is a high concentration of hydrogen peroxide, and as the reaction progresses, the catalase enzyme breaks down more and more hydrogen peroxide molecules. Therefore, the number of reactant break down increases over time.

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24.

At 0°C, enzyme action …… because the rate of formation of enzyme substrate complex ……... . But raising the temperature, …….. the formation rate. Therefore enzyme action ………. .
- Decreases / increases / speeds up / stops.
- Increases / stops / decreases / speeds up.
- Speeds up / increases / stops / decreases.
- Stops / decreases / speeds up / increases.
Correct Answer

A. Stops / decreases / speeds up / increases.

Explanation

At 0°C, enzyme action stops because the rate of formation of enzyme-substrate complex decreases. But raising the temperature speeds up the formation rate. Therefore, enzyme action increases.

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25.

The beginning of the reaction between the catalase and the hydrogen peroxide in the graph below represents …...
- Low rate of reaction
- High rate of reaction
- End of the reaction
- All of the them
Correct Answer

A. High rate of reaction

Explanation

The beginning of the reaction between the catalase and the hydrogen peroxide is represented by a high rate of reaction in the graph. This is indicated by a steep slope at the start of the graph, showing that the reaction is occurring rapidly. As time progresses, the rate of reaction may decrease, leading to a lower rate of reaction. Therefore, the correct answer is "High rate of reaction."

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26.

Which of the following statement is/are correct about Enzyme?
- Both (i) and (ii) are correct
- Both (i) and (iii) are correct
- (i), (ii) and (iii) are correct
- All the above are correct
Correct Answer

A. All the above are correct

Explanation

All the statements (i), (ii), and (iii) are correct about Enzyme.

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27.

What monomer subunits join together to form starch in a metabolic reaction?
- Sucrose
- Glucose
- Glycogen
- Cellulose
Correct Answer

A. Glucose

Explanation

Glucose monomer subunits join together to form starch in a metabolic reaction. Starch is a polysaccharide that serves as a storage form of energy in plants. Glucose molecules link together through glycosidic bonds to form long chains of starch. This allows plants to store excess glucose for later use when energy is needed. Sucrose, glycogen, and cellulose are also polysaccharides, but they are not the monomer subunits that form starch.

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28.

Which of the following best describes the lock and key theory of enzyme action?
- The enzyme and substrate have identical shapes, like a “lock and key.”
- The enzyme is the “lock” into which the substrate, or the “key,” fits.
- Once the enzyme and substrate have joined, they are locked together and cannot be separated.
- The substrate is the “lock” into which the enzyme, or the “key,” fits.
Correct Answer

A. The enzyme is the “lock” into which the substrate, or the “key,” fits.

Explanation

The lock and key theory of enzyme action suggests that the enzyme acts as a "lock" and the substrate acts as the "key." The enzyme has a specific shape that allows it to bind with a specific substrate, similar to how a key fits into a lock. Once the enzyme and substrate have joined, they form an enzyme-substrate complex and undergo a chemical reaction. This theory emphasizes the specificity of enzyme-substrate interactions, as only a specific substrate can bind to a specific enzyme due to their complementary shapes.

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29.

Without digestive enzymes, animals would not be able to break down food molecules quickly enough to provide themselves with the energy and nutrients they need to survive. Which of the following would most likely happen in the absence of digestive enzymes in an animal’s body?
- The rate of digestion reactions would increase extremely.
- The digestion reactions would proceed but at an extremely lower rate.
- The digestion reactions would stop completely.
- The rate of digestion reactions would remain the same.
Correct Answer

A. The digestion reactions would proceed but at an extremely lower rate.

Explanation

Digestive enzymes play a crucial role in breaking down food molecules into smaller, absorbable units. Without these enzymes, the digestion reactions would still occur, but at a much slower pace. This is because the enzymes are responsible for speeding up the chemical reactions involved in digestion. Without them, the process would be significantly slowed down, resulting in a much lower rate of digestion reactions.

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30.

Fill in the blank: The reactant that an enzyme will bind to, due to its complementary shape, is a/an …………..
- Active site
- Protein
- Catalyst
- Substrate
- Product
Correct Answer

A. Substrate

Explanation

Enzymes are proteins that act as catalysts in biochemical reactions. They have a specific region called the active site where they bind to a molecule called the substrate. The active site and the substrate have complementary shapes, allowing them to fit together like a lock and key. This binding of the substrate to the active site facilitates the reaction, allowing the enzyme to catalyze the conversion of the substrate into a product. Therefore, the correct answer is substrate.

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31.

From the experiment of the action of catalase enzyme on the hydrogen peroxide, the catalase works best at a pH of ….....
- 1
- 4
- 7
- 10
Correct Answer

A. 7

Explanation

Catalase is an enzyme that helps break down hydrogen peroxide into water and oxygen. Enzymes are sensitive to changes in pH, and their activity can be affected by it. In this experiment, the catalase enzyme works best at a pH of 7. This is because pH 7 is considered neutral, and many enzymes have an optimal pH around this range. At pH 7, the enzyme's active site is in the proper conformation to bind with the hydrogen peroxide substrate and catalyze the reaction efficiently.

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32.

In the reaction involving the catalase and the hydrogen peroxide, as the reaction time proceeds, the slope of the graph flattens, indicating a(an) …....
- Decreased production of oxygen
- Increased production of oxygen
- Increased production of H⁺
- End of the reaction
Correct Answer

A. Decreased production of oxygen

Explanation

As the reaction time proceeds, the slope of the graph flattens, indicating that the rate of oxygen production is decreasing. This suggests that the catalase enzyme is becoming saturated with hydrogen peroxide and is unable to catalyze the reaction at the same rate as before. Therefore, the correct answer is decreased production of oxygen.

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33.

The prefix "nano" comes from a ......
- French word meaning billion
- Greek word meaning dwarf
- Spanish word meaning particle
- Latin word meaning invisible
Correct Answer

A. Greek word meaning dwarf

Explanation

The prefix "nano" comes from the Greek word meaning dwarf. This is because the prefix "nano" is used to indicate a billionth of a unit, which is a very small amount. The Greek word for dwarf, "nanos," is used to convey the idea of something being extremely small or tiny, which aligns with the meaning of the prefix "nano."

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34.

The following graph shows the effect of altering a factor on the rate of an enzyme controlled reaction. What is shown on the x axis?
- PH
- Temperature
- Substrate concentration
- Enzyme concentration
Correct Answer

A. Temperature

Explanation

The x-axis on the graph shows the factor that is being altered, and the effect of this alteration on the rate of an enzyme controlled reaction is being measured. The correct answer is "Temperature" because the graph is showing how changing the temperature affects the rate of the reaction.

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35.

Enzymes are completely destroyed at …… ^OC or above.
- 40
- 60
- 10
- 37
Correct Answer

A. 60

Explanation

Enzymes are proteins that catalyze chemical reactions in living organisms. They have a specific three-dimensional structure that is essential for their function. When exposed to high temperatures, enzymes can denature, meaning their structure becomes disrupted and they lose their catalytic activity. The given answer, 60°C, suggests that enzymes are completely destroyed at this temperature or above. This is because at such high temperatures, the bonds that maintain the enzyme's structure are broken, rendering the enzyme non-functional.

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36.

Which of the statements regarding enzymes is false?
- Enzymes are proteins that function as catalysts.
- Enzymes are specific.
- Enzymes provide activation energy for reactions.
- Enzyme activity can be regulated.
- Enzymes may be used many times for a specific reaction.
Correct Answer

A. Enzymes provide activation energy for reactions.

Explanation

Enzymes are proteins that function as catalysts, meaning they speed up chemical reactions without being consumed in the process. Enzymes are specific, meaning they only catalyze specific reactions. Enzyme activity can be regulated, allowing cells to control the rate of reactions. Enzymes may be used many times for a specific reaction, as they are not consumed during the reaction. However, enzymes do not provide activation energy for reactions. Activation energy is the energy required to start a reaction, and enzymes lower the activation energy required for a reaction to occur.

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37.

The following graph shows the effect of a factor on the activity of two enzymes.What are the enzymes (X) and (Y)?
- X is amylase, Y is trypsin
- X is catalase, Y is pepsin
- X is amylase, Y is trypsin
- X is pepsin, Y is trypsin
Correct Answer

A. X is pepsin, Y is trypsin

Explanation

Based on the information given in the graph, it can be concluded that the factor being tested has a greater effect on the activity of enzyme Y compared to enzyme X. Therefore, the correct answer is X is pepsin, Y is trypsin.

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38.

Which of the following reaction is catalyzed by Lipase?
- Breaking of bonds
- Formation of bonds
- Intramolecular rearrangement of bonds
- Transfer of group from one molecule to another
Correct Answer

A. Breaking of bonds

Explanation

Lipase is an enzyme that catalyzes the hydrolysis of ester bonds in lipids, resulting in the breaking of bonds between fatty acids and glycerol. This reaction allows for the breakdown of fats and oils into smaller molecules, such as fatty acids and glycerol, which can be further metabolized by the body for energy or other purposes. Therefore, the correct answer is "Breaking of bonds".

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39.

Most enzymes work best at a pH of about ……..
- 5
- 6
- 7
- 8
Correct Answer

A. 7

Explanation

Most enzymes work best at a pH of around 7 because this is the pH at which their active site is most stable and can effectively bind to the substrate. At higher or lower pH levels, the active site may become denatured or the charges on the enzyme and substrate may be disrupted, preventing proper binding and reducing enzyme activity. Therefore, a pH of 7 is optimal for most enzymes to function efficiently.

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40.

The following graph shows the effect of a factor on the activity of two enzymes. What should be shown on the x axis?
- Temperature
- PH
- Substrate concentration
- Enzyme concentration
Correct Answer

A. pH

Explanation

The x-axis of the graph should represent the factor that is being tested, which in this case is the effect of a factor on the activity of two enzymes. The graph shows the effect of this factor on the enzymes, so the x-axis should represent the different levels or values of the factor being tested. In this case, the factor being tested is pH, so pH should be shown on the x-axis.

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41.

Why are amylases, proteases and lipases added to detergents? Because ....
- Amylases break down starch stains / proteases break down protein stains / lipases break down fat and grease stains.
- Amylases break down protein stains / proteases break down starch stains / lipases break down fat and grease stains.
- Amylases break down starch stains / proteases break down fat and grease stains / lipases break down protein stains.
- Amylases break down fat and grease stains / proteases break down protein stains / lipases break down starch stains.
Correct Answer

A. Amylases break down starch stains / proteases break down protein stains / lipases break down fat and grease stains.
42.

The reaction stops completely at high temperature due to the ……. of the enzyme.
- Destruction
- Formation
- Reversibility
- Activation
Correct Answer

A. Destruction

Explanation

At high temperatures, the enzyme undergoes destruction or denaturation. This means that the enzyme's structure and shape are altered, leading to a loss of its catalytic activity. The destruction of the enzyme at high temperatures prevents it from effectively catalyzing the reaction, causing the reaction to stop completely.

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43.

The reaction rate of pepsin enzyme is high at a pH of …..
- 5 – 6
- 7
- 8 – 9
- 1 – 2
Correct Answer

A. 1 – 2

Explanation

The reaction rate of pepsin enzyme is high at a pH of 1-2 because pepsin is an enzyme that functions in the acidic environment of the stomach. The low pH helps to denature proteins and activate pepsin, allowing it to break down proteins into smaller peptides. Therefore, a pH of 1-2 is the optimal range for pepsin activity.

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44.

Which statement BEST describes why a continued increase in pH above the optimum results in a sharp decrease in the enzyme activity as shown in the graph below?
- The enzyme is denatured.
- The enzyme cannot bind so well to the substrate.
- Changes in pH alter the shape of an enzyme's active site.
- All of them.
Correct Answer

A. All of them.

Explanation

A continued increase in pH above the optimum can result in a sharp decrease in enzyme activity due to multiple factors. Firstly, the high pH can denature the enzyme, causing it to lose its shape and function. Additionally, changes in pH can also alter the shape of the enzyme's active site, making it less able to bind to the substrate effectively. Therefore, all of these factors contribute to the decrease in enzyme activity.

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45.

Enzymes that have to be used as detergent composite must possess the following characters …..
- Stability at low temperature and high pH
- Stability at low temperature and low pH
- Stability at high temperature and low pH
- Stability at high temperature and high pH
Correct Answer

A. Stability at high temperature and high pH

Explanation

Enzymes used as detergent composites need to be stable at high temperatures and high pH levels. This is because detergents are often used in high-temperature wash cycles and the pH of the detergent solution can be alkaline. Enzymes that are not stable under these conditions would denature and lose their activity, rendering them ineffective as detergent additives. Therefore, stability at high temperature and high pH is a crucial characteristic for enzymes used in detergents.

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46.

In an alkaline medium, the rate of pepsin ……..
- Increases
- Decreases then stop
- Decreases then increases
- Is not affected
Correct Answer

A. Decreases then stop

Explanation

In an alkaline medium, pepsin, which is an enzyme responsible for protein digestion in the stomach, becomes denatured and loses its activity. This causes the rate of pepsin to initially decrease. Eventually, the alkaline environment completely stops the activity of pepsin, leading to a complete halt in the rate of pepsin.

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47.

Which graph shows the effect of temperature on the activity of an enzyme?
- A
- B
- C
- D
Correct Answer

A. A

Explanation

Graph A shows the effect of temperature on the activity of an enzyme because it shows a gradual increase in activity as temperature increases, followed by a sharp decrease in activity at higher temperatures. This pattern is consistent with the concept of enzyme activity being influenced by temperature, where activity typically increases with temperature until it reaches an optimal temperature, after which it rapidly declines. Graphs B, C, and D do not show this pattern and therefore do not represent the effect of temperature on enzyme activity.

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48.

The pancreatic juice does not contain …….
- Pancreatic amylase
- Lipase
- Pepsin
- Trypsin
Correct Answer

A. Pepsin

Explanation

The pancreatic juice is a fluid secreted by the pancreas that aids in digestion. It contains enzymes such as pancreatic amylase, lipase, and trypsin, which help break down carbohydrates, fats, and proteins respectively. However, pepsin is not found in pancreatic juice. Pepsin is an enzyme that is produced in the stomach and helps in the digestion of proteins.

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49.

What is the main advantage of using nanotechnology for drug delivery?
- Successful delivery to the targeted region of the body
- Efficient encapsulation of the drug
- Drug stability
- All of these
Correct Answer

A. All of these

Explanation

The main advantage of using nanotechnology for drug delivery is that it encompasses all of the given options. Nanotechnology allows for successful delivery of drugs to the targeted region of the body, ensuring that the medication reaches the intended site of action. It also enables efficient encapsulation of the drug, protecting it from degradation and enhancing its bioavailability. Additionally, nanotechnology contributes to drug stability, preventing premature drug breakdown and ensuring the drug remains effective until it reaches its target. Therefore, all of these factors make nanotechnology a highly advantageous method for drug delivery.

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Unit 1 Chapter 3 (1st Secondary) Biology

The enzyme catalase catalyzes the reaction that breaks down hydrogen peroxide into water and oxygen. The graph shows how much oxygen is produced over time when this reaction occurs with and without catalase. Which of the following statements correctly describes the trend shown?

Quiz Preview

In the reaction involving the catalase enzyme and the hydrogen peroxide, the enzyme breaks the reactant into …….

The graph below illustrates the free energy of a biochemical reaction, once in the absence of an enzyme and another time in the presence of a specific enzyme. In the presence of the enzyme, the energy of activation of the reaction is lowered from ………. to ……..

Oxidation of glucose during cellular respiration is considered a process of …..

Enzymes are characterized than other chemical catalysts in that they …….

The graph provided shows the reaction profile of a biological reaction. Which letter indicates the activation energy?

Why does the graph level-off at point (B) if you know that the reaction is done at constant temperature and pH ?

If in a certain enzymatic reaction, an enzyme (E) works on a substrate (S). What makes the rate of reaction constant after some time of starting the reaction?

Enzyme catalyzing rearrangement of atomic groupings without altering molecular weight or number of atoms is ……

When you eat a large meal, the _____ activity called digestion takes the biomolecules you consumed and breaks them down into smaller molecules.

The relationship between an enzyme and a reactant molecule can best be described as ……….

According to the figure below, Which of the following statements is incorrect ......

Which of the following statements is true about metabolism?

In some metabolic reactions, large molecules are broken down into smaller ones. What biological reaction breaks down glucose in cells to release energy?

Which is not true about enzymes?

Assuming that rolling a huge ball across a hill as in the figure below, represents a biochemical reaction that takes place without enzyme. So the energy of activation can be illustrated by ……..

“Lock and key theory” is related with …....

Why is a period of intense exercise often followed by heavy breathing?

Look at the following diagram, which represents the energy diagram for a chemical reaction. Which point on the diagram represents the point at which the transition state exists?

Which of the following statements correctly links enzymes, substrates, and active sites?

In humans salivary amylase enzyme breaks down starch. What is the optimum pH for this reaction?

In the reaction involving the catalase and the hydrogen peroxide, at the beginning time, the …..

At 0°C, enzyme action …… because the rate of formation of enzyme substrate complex ……... . But raising the temperature, …….. the formation rate. Therefore enzyme action ………. .

The beginning of the reaction between the catalase and the hydrogen peroxide in the graph below represents …...

Which of the following statement is/are correct about Enzyme?

What monomer subunits join together to form starch in a metabolic reaction?

Which of the following best describes the lock and key theory of enzyme action?

Without digestive enzymes, animals would not be able to break down food molecules quickly enough to provide themselves with the energy and nutrients they need to survive. Which of the following would most likely happen in the absence of digestive enzymes in an animal’s body?

Fill in the blank: The reactant that an enzyme will bind to, due to its complementary shape, is a/an …………..

From the experiment of the action of catalase enzyme on the hydrogen peroxide, the catalase works best at a pH of ….....

In the reaction involving the catalase and the hydrogen peroxide, as the reaction time proceeds, the slope of the graph flattens, indicating a(an) …....

The prefix "nano" comes from a ......

The following graph shows the effect of altering a factor on the rate of an enzyme controlled reaction. What is shown on the x axis?

Enzymes are completely destroyed at …… OC or above.

Which of the statements regarding enzymes is false?

The following graph shows the effect of a factor on the activity of two enzymes.What are the enzymes (X) and (Y)?

Which of the following reaction is catalyzed by Lipase?

Most enzymes work best at a pH of about ……..

The following graph shows the effect of a factor on the activity of two enzymes. What should be shown on the x axis?

Why are amylases, proteases and lipases added to detergents? Because ....

The reaction stops completely at high temperature due to the ……. of the enzyme.

The reaction rate of pepsin enzyme is high at a pH of …..

Which statement BEST describes why a continued increase in pH above the optimum results in a sharp decrease in the enzyme activity as shown in the graph below?

Enzymes that have to be used as detergent composite must possess the following characters …..

In an alkaline medium, the rate of pepsin ……..

Which graph shows the effect of temperature on the activity of an enzyme?

The pancreatic juice does not contain …….

What is the main advantage of using nanotechnology for drug delivery?

Enzymes are completely destroyed at …… ^OC or above.