2001 Question 1.
Jane, a 32-year-old agricultural botanist, goes to work at a scientific research station in the
Andes at an altitude of 5000 m. Atmospheric pressure at this altitude is 400 mmHg. On arrival
Jane feels unwell and reports to the medical staff at the station. She is breathing deeply and
rapidly and her minute ventilation (litres/min; volume of gas expired in 1 minute) is greater than
normal. An arterial blood sample yields the following information:
pH 7.47 (7.35 - 7.45)
PaO2 37 mmHg (80 - 100 mmHg)
PaCO2 32 mmHg (35 - 45 mmHg)
AHCO3 22.5 mmol/L (24 - 32 mmol/L)
(a) What factors control minute ventilation?
[10 minutes]
(b) Why is Jane's minute ventilation increased?
[5 minutes]


2002 - Question 3
Describe properties or functions of haemoglobin which contribute to its role in sustaining activity in skeletal muscle during aerobic exercise.
(I0 minutes)


2002 - Question 4
Dinitrophenol is an uncoupler of oxidative phosphorylation in cells and was used, in the past, as a herbicide. What would you expect to observe in a person acutely poisoned with DNP? In your answer:
(i) explain the normal process of oxidative phosphorylation
(ii) indicate how this is modified by an uncoupler
(iii) briefly describe any changes that you would expect in the person's temperature,
respiration rate and/or ability to jog to the hospital emergency room.
(15 minutes)


2003 - 2. A previously-healthy 39-year-old financial advisor has attempted suicide by carbon monoxide poisoning using his car exhaust. He is found unconscious but still breathing, by a neighbour who rushes him to a nearby Emergency Department.
The Medical Officer takes an arterial blood sample and begins O2 at 12 litres/min by mask.
Finding for the arterial blood sample were as follows:
Result Reference Range
P02 87 mmHg (80 - 100)
PCO, 30 mmHg (35 - 45)
HCO3' 18 mmol/L (21 - 28)
pH 7.30 (7.35 - 7.45)
Oxyhaemoglobin 56% (94-100)
Methaemoglobin 0.7% (<2%)
Carboxyhaemoglobin 41% (l. - 3% non-smoker, 10 - 15% heavy smoker)
(a) Consider gas exchange between lungs and tissues in this marl while he is breathing CO-rich air. Describe gas exchange been the alveoli and blood in the man’s lungs; and describe gas exchange between blood and an energy-consuming tissue, such as liver. Indicate how these processes differ from normal when CO is present. In your answer, explain the abnormal “blood gas” values.
[12 min]
(h) Discuss the processes for generating ATP in liver in this man at the time of taking the arterial blood sample. Qm1m_e the metabolic pathways likely to be involved in ATP generation, explaining how the exposure to C0 would change this from normal.
[13 min]


Hydrogen cyanide is volatile and readily absorbed through the lungs. Cyanide binds to heme of cytochrome a/a3 (otherwise known as the cytochrome oxidase complex or complex IV) and prevents transfer of electrons to O2.
a) Explain why cyanide exposure can be lethal, outlining the normal biochemical processes, disrupted by cyanide, which are vital to life.
(10 marks)
b) What would be the effect of cyanide poisoning on the activity of the tricarboxylic acid (TCA) cycle in cells? Explain how the effect occurs.
(4 marks)


2005 - Mike Driscoll is a previously healthy 48 year old technical specialist at a copper plating factory who is called out from the engineering office to check a leaking valve on the factory floor. Some time after the call-out, Mike stumbles in the path of a fork-lift driver moving empty palettes. Mike seems limp and disoriented and mutters something about headache, dizziness and nausea.
With some difficulty, the driver gets Mike onto a palette and drives him to the factory first aid station. The attendant has limited skills but notes Mike’s weakness and lethargy, disorientation and apparent shortness of breath, with rapid respiration rate. The attendant calls an ambulance.
Question 6.
List key information about Mike and his problem. Then outline two hypotheses you consider most likely to account for Mike’s problem. For each hypothesis, briefly outline mechanisms relating the hypothesis to Mike’s condition.
(13 marks)
Question 7.
The ambulance arrives quickly and transports Mike to the nearest hospital emergency department. Assuming that Mike is unable to give any useful history, indicate 3 things you would look for on physical examination, or test for, once Mike arrives in the Emergency Department. Indicate how the results of such investigations might be interpreted to help confirm, eliminate or differentiate between your hypotheses.
(12 marks)
Soon after the laboratory results are received, there is a telephone call from the factory to indicate that the valve Mike went to check was in a line carrying a cyanide solution used in the factory process. Although the valve is no longer leaking, it seems possible Mike has come in contact with cyanide salt crystals around the valve seal.
One of the emergency physicians comments that this is the first case of cyanide poisoning he has seen and that Mike seems to have been lucky in that he received a small exposure.
Question 9.
Cyanide binds to the Fe3+ in the haem group of cytochrome aa3 (cytochrome oxidase) and prevents transfer of electrons to O2.
a) Why was Mike weak after his cyanide exposure? Explain the key biochemical processes affected by cyanide that could lead to muscle weakness.
(12 marks)
b) How would you expect the relative oxygen saturations of venous and arterial blood in Mike to compare with the relative saturations in normal people? Explain.
(4 marks)
c) What effect would you expect cyanide to have on CO2 production by cells? Explain, indicating which metabolic events account for the bulk of CO2 production and why cyanide would affect these events.
(6 marks)
d) Why was Mike’s respiration rate increased following his moderate cyanide exposure? Suggest a likely sequence of events from the initial action of the cyanide through to the increased respiration rate.
(8 marks)


2006 - Question 3.
(a) Discuss how the properties of haemoglobin facilitate oxygen delivery to tissues in the body under resting conditions.
(9 marks)
(b) Describe the effects of vigorous exercise on oxygen delivery by haemoglobin.
(4 marks)
(c) The presence of CO in inspired air substantially reduces O2 delivery to tissues. Explain why this is so.
(4 marks)


2007 - Question 2.
(a) Draw a normal Haemoglobin (Hb) oxygen dissociation curve showing variation of % Hb saturation
and also O2 content (ml O2 per 100 ml blood) with PO2.
(3 marks)
(b) On the figure, show how much O2 is released when the PO2 falls from 100 mm Hg (eg in the lungs)
to 40 mm Hg (eg in tissues). Give an approximate value in ml O2/100 ml blood.
(2 marks)
(c) Explain how relatively vigorous exercise in skeletal muscle affects O2 release from Hb in that
exercising tissue.
(5 marks)


(d) Describe how CO2 is transported in the blood.
(5 marks)2008 - A 16 year old girl, Carly MacNab is found around midnight by Salvation Army officers in the basement of an abandoned factory, used by runaways and homeless people for temporary shelter. Another girl, Peta, has brought the officers to the basement. Carly appears thin but moderately well nourished. She has no obvious injuries. She has only light clothes but has kept warm by sleeping close to a wood burning combustion heater apparently left by previous squatters.
Peta tells the officers that Carly had told her about the basement. “When I arrived about 10, Carly was huddling by the heater. She was maybe a bit confused but OK. She said she had a headache and wanted to throw up. I don’t think she has had any food for a day or so. Later she seemed to pass out and I got worried.”
Carly is now semi-comatose and unresponsive. She seems to be breathing rapidly.
Question 6.
List key information about Carly, then outline two hypotheses that you consider most likely to account for her problems. For each hypothesis, briefly outline mechanisms relating the hypothesis to Carly’s condition.
(12 marks)
The Salvation Army officers take Carly to a nearby hospital Emergency Department.
Question 7.
Outline information that you would seek from a physical examination or laboratory tests to investigate and distinguish between your hypotheses. Explain how you would interpret possible findings in relation to your hypotheses.
(13 marks)
In the Emergency Department, Carly is lethargic and disoriented. She has no apparent injuries or bites. Her colour appears normal. Her blood pressure is 140/90, pulse 110, respiration rate 28, and temperature 36.7°c.
An arterial blood sample is taken for analysis. The results are as follows:
Reference Range
(arterial blood)
PO2 89 mmHg (80-100 mmHg)
PCO2 31 mmHg (35-45 mmHg)
HCO3-19 mmol/L (21-28 mmol/L)
pH 7.32 (7.35-7.45)
Total haemoglobin
32 g/L (115-160 g/L) (Female)
Oxyhaemoglobin 59%
Carboxyhaemoglobin 38% (non-smokers 1-3%, heavy smokers 10-15%)
Glucose 4.1 mmol/L (3.0-5.5 mmol/L)
beta-hydroxybutyrate < 0.3 mmol/L (<0.3 mmol/L)
Question 8.
Restate your previous hypotheses in a few words and indicate how the new findings weigh for or against these hypotheses. Indicate what is now your preferred hypothesis to explain Carly’s condition, summarising in a sentence or two how this explains her lethargic, disoriented state (details of mechanisms may be covered in subsequent questions).
(8 marks)
Question 9.
a) Explain how the levels of oxyhaemoglobin and carboxyhaemoglobin are relevant to oxygen delivery to Carly’s tissues.
(6 marks)
b) Briefly explain the PO2 level observed.
(2 marks)
c) What are the metabolic consequences for Carly’s tissues of altered O2 delivery? Explain why these occur.
(9 marks)
d) What treatment is appropriate for Carly? Explain the rationale for this.
(3 marks)
Question 10.
Suggest an explanation for the PCO2, pH and bicarbonate results for Carly.
(5 marks)