📌 Grade 12 biology
📍 Unit 3: Enzymes
Enzymes: mid Exam
Part I: Structure and Function of Enzymes
1.What is the primary role of enzymes in biological systems?
A. To provide energy for cellular reactions
B. To act as structural components in cells
C. To lower the activation energy of biochemical reactions
D. To alter the equilibrium of chemical reactions
2.Enzymes are composed primarily of which type of biomolecule?
A. Lipids
B. Carbohydrates
C. Nucleic acids
D. Proteins
3.Which part of the enzyme binds to the substrate?
A. Allosteric site
B. Active site
C. Coenzyme
D. Product binding site
4.What is the effect of extreme temperatures on enzyme activity?
A. Enzyme activity increases indefinitely
B. Enzymes become more specific to substrates
C. Enzymes may denature and lose function
D. Enzyme activity is unaffected
Part II: Enzyme Specificity and Mechanisms
1.Which of the following best describes the "lock and key" model of enzyme activity?
A. The enzyme changes shape to fit the substrate
B. The enzyme has a specific shape complementary to the substrate
C. Substrates compete for the enzyme’s active site
D. The enzyme forms multiple products from a single substrate
2.Which term describes a molecule that competes with the substrate for binding to the enzyme's active site?
A. Noncompetitive inhibitor
B. Competitive inhibitor
C. Coenzyme
D. Activator
3.What happens to an enzyme after it catalyzes a reaction?
A. It is permanently altered and degraded
B. It is recycled and reused for the same reaction
C. It is converted into a substrate
D. It becomes inactive for a short time
Part III: Factors Affecting Enzyme Activity
1.Which of the following factors does NOT affect enzyme activity?
A. Temperature
B. Substrate concentration
C. pH
D. Amount of sunlight
2.An enzyme exhibits optimal activity at a pH of 7. What happens if the pH decreases to 4?
A. Enzyme activity increases
B. Enzyme activity decreases
C. Enzyme structure becomes more stable
D. No change occurs in enzyme activity
3.What is the role of cofactors in enzymatic reactions?
A. They alter the enzyme's shape permanently
B. They prevent the substrate from binding
C. They assist in stabilizing the enzyme-substrate complex
D. They denature the enzyme at high temperatures
Part IV: Applications of Enzymes
1.Which of the following enzymes is involved in the breakdown of starch?
A. Lipase
B. Protease
C. Amylase
D. Lactase
2.What type of enzyme catalyzes the conversion of hydrogen peroxide into water and oxygen?
A. Oxidase
B. Catalase
C. Hydrolase
D. Lyase
3.In industrial processes, enzymes are used because they:
A. Increase reaction times significantly
B. Function well under all conditions
C. Are reusable and work efficiently under mild conditions
D. Are inexpensive to produce
@Ethioquizzes
@Ethiomatrichub
@Ethiomatrics
📍 Unit 3: Enzymes
Enzymes: mid Exam
Part I: Structure and Function of Enzymes
1.What is the primary role of enzymes in biological systems?
A. To provide energy for cellular reactions
B. To act as structural components in cells
C. To lower the activation energy of biochemical reactions
D. To alter the equilibrium of chemical reactions
2.Enzymes are composed primarily of which type of biomolecule?
A. Lipids
B. Carbohydrates
C. Nucleic acids
D. Proteins
3.Which part of the enzyme binds to the substrate?
A. Allosteric site
B. Active site
C. Coenzyme
D. Product binding site
4.What is the effect of extreme temperatures on enzyme activity?
A. Enzyme activity increases indefinitely
B. Enzymes become more specific to substrates
C. Enzymes may denature and lose function
D. Enzyme activity is unaffected
Part II: Enzyme Specificity and Mechanisms
1.Which of the following best describes the "lock and key" model of enzyme activity?
A. The enzyme changes shape to fit the substrate
B. The enzyme has a specific shape complementary to the substrate
C. Substrates compete for the enzyme’s active site
D. The enzyme forms multiple products from a single substrate
2.Which term describes a molecule that competes with the substrate for binding to the enzyme's active site?
A. Noncompetitive inhibitor
B. Competitive inhibitor
C. Coenzyme
D. Activator
3.What happens to an enzyme after it catalyzes a reaction?
A. It is permanently altered and degraded
B. It is recycled and reused for the same reaction
C. It is converted into a substrate
D. It becomes inactive for a short time
Part III: Factors Affecting Enzyme Activity
1.Which of the following factors does NOT affect enzyme activity?
A. Temperature
B. Substrate concentration
C. pH
D. Amount of sunlight
2.An enzyme exhibits optimal activity at a pH of 7. What happens if the pH decreases to 4?
A. Enzyme activity increases
B. Enzyme activity decreases
C. Enzyme structure becomes more stable
D. No change occurs in enzyme activity
3.What is the role of cofactors in enzymatic reactions?
A. They alter the enzyme's shape permanently
B. They prevent the substrate from binding
C. They assist in stabilizing the enzyme-substrate complex
D. They denature the enzyme at high temperatures
Part IV: Applications of Enzymes
1.Which of the following enzymes is involved in the breakdown of starch?
A. Lipase
B. Protease
C. Amylase
D. Lactase
2.What type of enzyme catalyzes the conversion of hydrogen peroxide into water and oxygen?
A. Oxidase
B. Catalase
C. Hydrolase
D. Lyase
3.In industrial processes, enzymes are used because they:
A. Increase reaction times significantly
B. Function well under all conditions
C. Are reusable and work efficiently under mild conditions
D. Are inexpensive to produce
Answers
Part l
1.C
2.D
3.B
4.C
Part ll
1.B
2.B
3.B
Part lll
1.D
2.B
3.C
Part Vl
1.C
2.B
3.C
@Ethioquizzes
@Ethiomatrichub
@Ethiomatrics