ijmb model questions vol1 2022 biology | Essay

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Question 1 View Details
The labelled diagram shows a typical plant cell.
Question Parts
(a)
Identify and label any four organelles shown in the diagram.
(b)
State the principal function of each organelle you identified in part (a).
(c)
Explain how the presence of a cell wall and a large central vacuole help the plant cell maintain turgor pressure.
(d)
Compare the plant cell shown with a typical animal cell. List three structural differences and briefly state the functional significance of each difference.
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Question 2 View Details
The labelled diagram depicts the sequential stages of mitosis in a root‑tip cell.
Question Parts
(a)
Describe the principal events that occur in each stage of mitosis shown in the diagram.
(b)
If the total duration of mitosis in this cell is 60 minutes and the diagram indicates that metaphase occupies 30 % of the total time, calculate the duration of metaphase in minutes.
(c)
Explain why accurate chromosome segregation is essential for genetic stability and discuss two possible consequences of segregation errors.
(d)
The diagram shows cytokinesis following telophase. Discuss how the mechanism of cytokinesis differs between plant and animal cells, linking your discussion to structural features of the cells.
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Question 3 View Details
The diagram shows a longitudinal section of the human small intestine with its major regions and microscopic structures labelled.
Question Parts
(a)
Identify the three regions of the small intestine shown in the diagram and state one specific digestive function that occurs in each region.
(b)
Explain how the structural features of the villi and micro‑villi shown in the diagram enhance the efficiency of nutrient absorption.
(c)
If the total surface area of the small intestine without villi and micro‑villi is approximately 0.5 m², and the presence of villi increases this area to 250 m², estimate the factor by which the addition of micro‑villi further multiplies the surface area. Show the reasoning steps you use.
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Question 4 View Details
The diagram shows the major structures of the human respiratory system, each labelled from A to I.
Question Parts
(a)
State the correct sequential order of the labelled structures (A–I) that air passes through from the external environment to the alveolar sac.
(b)
Explain the process of external gas exchange that occurs in the alveolar sac.
(c)
A patient suffers from bilateral paralysis of the diaphragm. Using the diagram, discuss how this condition would affect ventilation and propose two clinical interventions that could assist the patient’s breathing.
(d)
Distinguish between external and internal respiration, indicating where each occurs and the primary purpose of each process.
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Question 5 View Details
A 25‑year‑old male runner participates in a marathon at sea level. His resting cardiac output is 5 L·min⁻¹, which rises to 20 L·min⁻¹ during intense exercise. His haemoglobin concentration is 15 g·dL⁻¹ and arterial oxygen saturation is 98 %. Assume each gram of haemoglobin can bind 1.34 mL O₂.
Question Parts
(a)
Calculate the maximum amount of oxygen (in mL O₂ per minute) that can be delivered to the tissues at rest and during intense exercise.
(b)
Explain how the structure of capillaries facilitates efficient exchange of nutrients and wastes between blood and tissues.
(c)
Discuss two physiological adjustments that occur in the respiratory system to support increased oxygen delivery during intense exercise.
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Question 6 View Details
A 30‑year‑old woman with normal kidney function undergoes a water‑loading test. She drinks 1 L of water within 10 minutes and her urine output over the next hour is measured.
Question Parts
(a)
Describe the sequence of events in the nephron that lead to the formation of urine, highlighting the roles of filtration, reabsorption and secretion.
(b)
If the measured urine volume is 800 mL with an osmolarity of 150 mOsm·kg⁻¹, calculate the amount of solute excreted and comment on the state of antidiuretic hormone (ADH) activity.
(c)
Explain how the counter‑current multiplier system in the loop of Henle contributes to the kidney’s ability to produce concentrated urine.
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Question 7 View Details
The plasma membrane of a cell contains various transport proteins that facilitate movement of substances across the membrane.
Question Parts
(a)
Describe three major types of membrane transport, giving one specific example of a substance or molecule that uses each type.
(b)
A cell is placed in a solution where the external Na⁺ concentration is 150 mM and the internal Na⁺ concentration is 15 mM. Explain how the Na⁺/K⁺‑ATPase contributes to maintaining this gradient and state how many Na⁺ ions are exported from the cell per molecule of ATP hydrolysed.
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Question 8 View Details
An enzyme-catalysed reaction is studied at different temperatures and pH values. The following observations are recorded:
Question Parts
(a)
Explain how temperature influences the enzyme’s Vmax and Km, citing the underlying molecular reasons.
(b)
At pH 7.0 the enzyme shows a Km of 0.5 mM and Vmax of 120 µmol·min⁻¹. At pH 5.0 the Km rises to 1.2 mM while Vmax remains unchanged. Discuss what these data reveal about the effect of pH on the enzyme’s active site and overall structure.
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Question 9 View Details
A 28‑year‑old woman presents with secondary amenorrhoea. Laboratory results show: FSH 3 IU/L, LH 2 IU/L, estradiol 30 pg/mL, prolactin 8 µg/L. MRI reveals a 6‑mm pituitary microadenoma. She reports regular menstrual cycles before the past eight months.
Question Parts
(a)
Explain the normal hormonal feedback mechanisms that regulate the menstrual cycle, indicating the phases in which FSH, LH and estradiol reach their peak concentrations.
(b)
Using the data provided, deduce the most likely site of dysfunction in the reproductive axis and justify your answer.
(c)
Predict the effect of surgical removal of the microadenoma on the hormone profile and menstrual pattern.
(d)
If the patient is treated with a continuous‑release GnRH agonist pump, describe the expected changes in FSH, LH and estradiol concentrations over the first four weeks and explain the clinical rationale.
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Question 10 View Details
In a population of a certain plant species, flower colour is determined by a single gene with two alleles: R (red) is dominant to r (white). A random sample of 200 plants shows 120 red and 80 white individuals.
Question Parts
(a)
Estimate the allele frequencies of R and r in the population assuming Hardy‑Weinberg equilibrium. Show all calculations.
(b)
Using the estimated allele frequencies, calculate the expected numbers of each genotype (RR, Rr, rr) in the sample and compare them with the observed phenotypic numbers. Discuss any deviation from Hardy‑Weinberg equilibrium.
(c)
A breeder crosses two heterozygous (Rr) plants. (i) Construct a Punnett square and state the probability that an offspring will have white flowers and be homozygous recessive. (ii) If 500 seeds are produced, estimate how many white‑flowered, homozygous recessive seedlings are expected.
(d)
A molecular marker gene (A) is linked to the R locus at a recombination frequency of 10 cM. Explain how this recombination frequency influences the segregation of the two traits in a test cross, and calculate the expected proportion of recombinant offspring.
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