ijmb model questions vol1 2019 biology | Essay

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Question 1 View Details
The labelled diagram shows a typical animal eukaryotic cell with its major organelles.
Question Parts
(a)
Identify three organelles directly involved in protein synthesis and briefly describe the specific role of each in the process.
(b)
Using the diagram, outline the complete pathway a newly synthesised secretory protein follows from its origin to its release outside the cell.
(c)
Discuss how the structural features of the plasma membrane, as shown in the diagram, enable selective transport of substances into and out of the cell.
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Question 2 View Details
The labelled diagram depicts the stages of mitosis in a somatic animal cell.
Question Parts
(a)
For each stage shown (prophase, metaphase, anaphase, telophase) describe the key chromosomal and spindle‑fiber events, referring to the diagram.
(b)
Explain the purpose of the spindle assembly checkpoint and discuss the possible cellular consequences if this checkpoint fails.
(c)
A diploid somatic cell of a species has a chromosome number of 2n = 24. Using the diagram, calculate the total number of chromosomes and the total number of chromatids present in the cell during metaphase and during anaphase. Show your reasoning.
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Question 3 View Details
The labelled diagram shows the human small intestine with three distinct regions marked A, B and C. Region A corresponds to the duodenum, region B to the jejunum and region C to the ileum. The diagram indicates the primary sites where carbohydrates, proteins and lipids are absorbed respectively.
Question Parts
(a)
State the label (A, B or C) that represents the main site of absorption for each of the following nutrients: carbohydrate, protein and lipid.
(b)
Briefly describe the main enzymatic processes that occur in each of the three regions to enable the absorption of the respective nutrient.
(c)
A meal contains 60 g of carbohydrate, 30 g of protein and 20 g of fat. Assuming complete digestion and absorption, calculate the total energy (in kilocalories) supplied by the absorbed nutrients. Use the Atwater factors: carbohydrate = 4 kcal g⁻¹, protein = 4 kcal g⁻¹, fat = 9 kcal g⁻¹. Show all steps of your calculation.
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Question 4 View Details
The diagram shows the human respiratory system with the labelled structures: A – Nasal cavity, B – Pharynx, C – Larynx, D – Trachea, E – Primary bronchi, F – Bronchioles, G – Alveolar sacs, H – Diaphragm, I – External intercostal muscles.
Question Parts
(a)
Describe the complete pathway that air follows from the external environment to the site of gas exchange, naming each structure it passes through.
(b)
The alveolar wall contains type I and type II pneumocytes. Explain the distinct functions of these two cell types in relation to respiration.
(c)
During vigorous exercise ventilation increases. Using the diagram, explain how the diaphragm (H) and the external intercostal muscles (I) contribute to this increased ventilation. Include the changes in thoracic cavity volume and pressure.
(d)
The partial pressure of oxygen in alveolar air is 100 mmHg and in the pulmonary capillary blood is 40 mmHg. (i) Calculate the diffusion gradient for oxygen. (ii) Discuss how this gradient drives the movement of oxygen into blood. (iii) If pulmonary fibrosis doubles the diffusion distance, qualitatively describe the expected effect on the rate of oxygen diffusion according to Fick’s law.
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Question 5 View Details
Consider the circulatory system of a healthy adult human.
Question Parts
(a)
Describe, in order, the complete pathway that blood follows from the left ventricle back to the right atrium, naming all major chambers and vessels encountered.
(b)
Cardiac output (CO) is the product of stroke volume (SV) and heart rate (HR). Given an average SV of 70 mL per beat and a resting HR of 72 beats min⁻¹, (i) calculate the resting cardiac output in litres per minute, showing all steps, and (ii) discuss two physiological mechanisms that increase cardiac output during moderate exercise.
(c)
When a person ascends to high altitude, the partial pressure of oxygen in alveolar air falls. Explain how this change influences the transport of oxygen in the blood and describe two adaptive responses that help maintain tissue oxygen delivery.
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Question 6 View Details
A 25‑year‑old male undergoes a routine health check. His plasma creatinine concentration is 0.9 mg dL⁻¹ and his body weight is 70 kg. The estimated glomerular filtration rate (GFR) can be approximated by the formula: GFR (mL min⁻¹) = (140 – age) × weight (kg) × 0.85 / serum creatinine (mg dL⁻¹).
Question Parts
(a)
Calculate the estimated GFR for this individual, showing each step of the computation.
(b)
Compare creatinine clearance with inulin clearance as measures of GFR, highlighting at least two limitations of using creatinine clearance.
(c)
For each of the following processes, state the primary nephron segment where it occurs and the main driving force:
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Question 7 View Details
The human body maintains internal stability through various homeostatic mechanisms. Answer the following questions on the regulation of blood glucose and body temperature.
Question Parts
(a)
Explain the negative‑feedback mechanism that controls blood‑glucose concentration, describing the roles of the pancreas, insulin, glucagon and the major target tissues.
(b)
Compare the regulation of body temperature with that of blood glucose, focusing on:
() Identify the controlled variable for each system.
() State the primary sensor and the integrating centre for each system.
() List the main effectors that bring about the corrective response.
(c)
Predict the physiological disturbances that would arise if the insulin response is impaired, and propose two possible clinical manifestations.
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Question 8 View Details
Effective coordination of body activities depends on the nervous system. Answer the following questions on neural pathways and clinical assessment of coordination.
Question Parts
(a)
Describe the complete pathway of the polysynaptic withdrawal (flexor) reflex, starting from the sensory receptor to the muscle response, and indicate the type of synapse at each relay.
(b)
Evaluate how damage to the dorsal column–medial lemniscal pathway would affect the ability to perform the reflex described in (a). Include discussion of sensory discrimination and motor response.
(c)
Propose a clinical test that could be used to assess the integrity of the coordination between the cerebellum and the motor cortex, describing the expected findings in a normal individual and in a patient with a cerebellar lesion.
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Question 9 View Details
A couple have been trying to conceive for two years without success. The female partner reports irregular menstrual cycles and occasional pelvic pain. Her physician suspects a hormonal imbalance affecting ovulation.
Question Parts
(a)
Describe the hormonal changes that occur during the follicular phase and explain how these hormones prepare the endometrium for possible implantation.
(b)
Explain the mechanism by which the luteinising hormone (LH) surge triggers ovulation and the subsequent formation of the corpus luteum.
(c)
Discuss two possible causes of infertility in this couple and suggest an appropriate investigative test for each cause.
(d)
Outline the main steps of in‑vitro fertilisation (IVF) that could be offered to this couple if natural conception remains unsuccessful.
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Question 10 View Details
In a remote community a rare autosomal recessive disorder (designated disorder X) has a carrier frequency of 1 in 25. A man affected by disorder X (homozygous recessive) wishes to marry a woman from the same community whose carrier status is unknown.
Question Parts
(a)
Calculate the probability that their first child will be affected by disorder X.
(b)
If the couple have three children, what is the probability that exactly one of them will be affected?
(c)
Explain the molecular basis of disorder X, describing how a mutation in the responsible gene leads to the observed clinical features.
(d)
Propose a concise genetic counselling plan for the couple, covering risk communication, reproductive options and any recommended investigations.
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