Practice Exam 7
VCE Biology Units 1 & 2 | Enzymes, Biochemical Pathways & Cell Division in Depth
✎ Complete ALL questions on paper before opening the Model Answers lesson. No notes. Aim for 1 minute per mark.
MULTIPLE CHOICE
Question 1 (1 mark)
Enzymes increase the rate of biochemical reactions by:
✎ Circle your answer
A) Increasing the temperature of the reaction
B) Lowering the activation energy required for the reaction to proceed
C) Being permanently consumed in the reaction
D) Changing the products of the reaction
Question 2 (1 mark)
The induced-fit model of enzyme action proposes that:
✎ Circle your answer
A) The active site is a rigid shape that never changes
B) The active site changes shape slightly as the substrate binds, improving the fit between enzyme and substrate
C) Any substrate can bind to any enzyme’s active site
D) Enzymes bind only to their products, not substrates
Question 3 (1 mark)
At a fixed enzyme concentration, as substrate concentration is increased from zero, the initial reaction rate:
✎ Circle your answer
A) Decreases steadily
B) Increases indefinitely with no upper limit
C) Increases, then levels off at a maximum rate (Vmax) as the enzyme becomes saturated
D) Remains constant throughout
Question 4 (1 mark)
Km, the Michaelis constant, refers to the substrate concentration at which:
✎ Circle your answer
A) The reaction rate equals zero
B) The reaction rate is at its absolute maximum
C) The reaction rate is exactly half of Vmax
D) The enzyme has been completely denatured
Question 5 (1 mark)
A competitive inhibitor reduces enzyme activity by:
✎ Circle your answer
A) Binding to a site other than the active site and permanently changing its shape
B) Structurally resembling the substrate and binding to the active site, blocking substrate access
C) Increasing the enzyme’s affinity for its substrate
D) Being incorporated permanently into the enzyme’s primary structure
Question 6 (1 mark)
The inhibitory effect of a competitive inhibitor can typically be overcome by:
✎ Circle your answer
A) Lowering the temperature
B) Increasing the substrate concentration
C) Increasing the pH only
D) Adding more inhibitor
Question 7 (1 mark)
A non-competitive (allosteric) inhibitor:
✎ Circle your answer
A) Binds at the active site, directly blocking the substrate
B) Binds at a site other than the active site, changing the enzyme’s shape so the active site no longer fits the substrate
C) Has no effect on enzyme activity
D) Can always be overcome by adding more substrate
Question 8 (1 mark)
A cofactor required for many enzymes to function is best described as:
✎ Circle your answer
A) An organic vitamin-derived molecule only
B) An inorganic ion (e.g. Zn2+, Mg2+) or other non-protein component needed for normal enzyme activity
C) A competitive inhibitor
D) A type of substrate
Question 9 (1 mark)
Which statement best describes the typical effect of temperature on enzyme reaction rate?
✎ Circle your answer
A) Rate increases indefinitely as temperature rises
B) Rate is unaffected by temperature change
C) Rate increases with temperature up to an optimum, then falls sharply as the enzyme denatures
D) Rate is highest at 0°C
Question 10 (1 mark)
End-product (feedback) inhibition in a metabolic pathway occurs when:
✎ Circle your answer
A) The first enzyme in the pathway is permanently destroyed
B) The final product of the pathway binds to an earlier enzyme (often allosterically), reducing its activity and slowing the entire pathway
C) Substrate concentration has no effect on the pathway
D) All enzymes in the pathway are inhibited equally regardless of product concentration
Question 11 (1 mark)
The main biological purpose of mitosis is to:
✎ Circle your answer
A) Produce genetically varied gametes for sexual reproduction
B) Produce two genetically identical diploid daughter cells for growth, repair or asexual reproduction
C) Halve the chromosome number
D) Generate new combinations of alleles through crossing over
Question 12 (1 mark)
During which stage of mitosis do sister chromatids separate and move toward opposite poles of the cell?
✎ Circle your answer
A) Prophase
B) Metaphase
C) Anaphase
D) Telophase
Question 13 (1 mark)
A key difference between cytokinesis in plant and animal cells is that:
✎ Circle your answer
A) Plant cells form a cleavage furrow, animal cells form a cell plate
B) Animal cells divide by forming a cleavage furrow that pinches the cell in two, while plant cells form a cell plate that develops into a new cell wall
C) Only animal cells undergo cytokinesis
D) Plant cells do not require cytokinesis after mitosis
Question 14 (1 mark)
Meiosis is necessary in sexually reproducing organisms mainly because it:
✎ Circle your answer
A) Doubles the chromosome number for the next generation
B) Halves the chromosome number, so that fertilisation restores the normal diploid chromosome number in offspring
C) Produces cells genetically identical to the parent
D) Only occurs in somatic cells
Question 15 (1 mark)
Crossing over, which contributes to genetic variation in gametes, occurs during:
✎ Circle your answer
A) Prophase I of meiosis, between non-sister chromatids of homologous chromosomes
B) Anaphase II of meiosis
C) Prophase of mitosis
D) Fertilisation
Question 16 (1 mark)
Nondisjunction refers to:
✎ Circle your answer
A) The normal separation of homologous chromosomes during anaphase I
B) The failure of homologous chromosomes or sister chromatids to separate correctly during meiosis, resulting in gametes with an abnormal chromosome number
C) The process of crossing over
D) A type of mitotic checkpoint
Question 17 (1 mark)
A person with three copies of chromosome 21 (trisomy 21, Down syndrome) most likely arose because of:
✎ Circle your answer
A) A frameshift mutation in a single gene
B) Nondisjunction of chromosome 21 during meiosis in a parent, producing a gamete with two copies of chromosome 21
C) Crossing over between non-homologous chromosomes
D) A mutation occurring only after fertilisation
Question 18 (1 mark)
Progression through the cell cycle is regulated mainly by fluctuating levels of:
✎ Circle your answer
A) Restriction enzymes
B) Cyclins, which bind and activate cyclin-dependent kinases (CDKs) at specific points in the cycle
C) DNA ligase
D) Chlorophyll
Question 19 (1 mark)
Which of the following is a defining characteristic of cancer cells that distinguishes them from normal cells?
✎ Circle your answer
A) Increased contact inhibition, limiting growth
B) Loss of normal control over the cell cycle, allowing uncontrolled division even without normal growth signals
C) Reduced rate of cell division compared to normal cells
D) Complete inability to divide
Question 20 (1 mark)
Compared with mitosis, meiosis differs in that it:
✎ Circle your answer
A) Produces two diploid daughter cells identical to the parent cell
B) Involves two successive divisions producing four haploid daughter cells that are genetically variable
C) Does not involve DNA replication beforehand
D) Occurs only in somatic (body) cells
SHORT ANSWER
Question 21 (4 marks)
Explain how the specific three-dimensional shape of an enzyme’s active site relates to its function, referring to the induced-fit model.
✎ Write your answer on paper
Question 22 (4 marks)
Describe, with reference to a rate versus substrate concentration graph, the effect of increasing substrate concentration on enzyme reaction rate at a fixed enzyme concentration.
✎ Write your answer on paper
Question 23 (5 marks)
Compare competitive and non-competitive inhibition, referring to where each inhibitor binds and how the effect of each could be distinguished experimentally.
✎ Write your answer on paper
Question 24 (4 marks)
Describe the role of cofactors and coenzymes in enzyme-catalysed reactions, referring to one named example of each.
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Question 25 (4 marks)
Describe the sequence of events that occur during mitosis in a plant cell, and outline one way cytokinesis in this cell would differ from cytokinesis in an animal cell.
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Question 26 (4 marks)
Explain how nondisjunction during meiosis I can result in aneuploidy, using Down syndrome (trisomy 21) as an example.
✎ Write your answer on paper
Question 27 (4 marks)
Describe three characteristics that distinguish cancer cells from normal, healthy cells.
✎ Write your answer on paper
Question 28 (3 marks)
Explain the role of cyclins and cyclin-dependent kinases (CDKs) in regulating progression through the cell cycle.
✎ Write your answer on paper
EXTENDED RESPONSE
Extended Response 1: Enzyme Kinetics Investigation
Question 29 (4 marks)
Extended Response 1: Enzyme Kinetics Investigation (a)
A student investigates the effect of temperature on the rate of the enzyme catalase, which breaks down hydrogen peroxide into water and oxygen. Describe the shape of the graph of reaction rate against temperature that the student would most likely obtain, and explain the trend at each part of the graph.
✎ Write your answer on paper
Extended Response 1: Enzyme Kinetics Investigation
Question 30 (3 marks)
Extended Response 1: Enzyme Kinetics Investigation (b)
The student then repeats the investigation at a constant, optimum temperature, but adds a fixed amount of a competitive inhibitor to some reaction mixtures. Predict and explain the effect this would have on a graph of reaction rate against substrate (hydrogen peroxide) concentration, compared with the uninhibited enzyme.
✎ Write your answer on paper
Extended Response 1: Enzyme Kinetics Investigation
Question 31 (3 marks)
Extended Response 1: Enzyme Kinetics Investigation (c)
Explain why a non-competitive inhibitor is sometimes described as behaving like an irreversible “poison” in a metabolic pathway, even at low concentrations, whereas a competitive inhibitor’s effect can often be minimised.
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Extended Response 2: Meiotic Errors and Chromosome Number Case Study
Question 32 (4 marks)
Extended Response 2: Meiotic Errors and Chromosome Number Case Study (a)
Explain the key differences between meiosis I and meiosis II in terms of what separates during anaphase and the genetic makeup of the resulting cells.
✎ Write your answer on paper
Extended Response 2: Meiotic Errors and Chromosome Number Case Study
Question 33 (3 marks)
Extended Response 2: Meiotic Errors and Chromosome Number Case Study (b)
Explain how nondisjunction occurring in meiosis I differs from nondisjunction occurring in meiosis II in terms of the gametes produced, and explain why the risk of nondisjunction is known to increase with increasing maternal age.
✎ Write your answer on paper
✓ Finished? Open the next lesson – Model Answers – to mark your work.
