How to Use This Set
These 40 questions cover the whole of Breathing and Exchange of Gases, in roughly the proportion the chapter itself gives each topic. Eight of them are the respiratory organs across the animal groups and the human passage from nostril to alveolus; four are the mechanism of breathing; nine - the largest single block - are the respiratory volumes and capacities; six are the exchange of gases and the partial pressures; eight are the transport of oxygen and carbon dioxide; three are the neural regulation of respiration; and two are the disorders and hypoxia. That weighting is not arbitrary. The volumes, the capacities and the partial pressures carry this chapter, and a student who can reproduce the four volumes with their ranges, add up the five capacities and read the partial pressure table across a row has already earned most of what this chapter is worth.
Sit the whole set in one go, and look nothing up. Answer every question in order, and mark every question where you were choosing between two options rather than certain. Those marked questions, not only the wrong ones, are your revision list afterwards. Check the answers only at the end, and when you check, go back to the number rather than to the option - the fix for a wrong answer here is almost always a figure or an address you had not fixed in memory.
The marking is +4 for a correct answer and -1 for a wrong one, and it is worth doing that arithmetic once. With four options and one of them right, a blind guess wins 4 marks once in every four attempts and loses 1 mark on the other three, so four blind guesses are worth about +1 mark between them - almost nothing, for four questions' worth of time. Cut the options down to two and the same four attempts are worth about +6. So the rule is not "never guess". It is never guess blind, and never spend time on a guess. On this chapter you can usually strike out at least one option at sight, because the wrong options are the other real numbers of the chapter - a different volume, a different partial pressure, a different percentage - and one of them will be a figure that belongs to a completely different quantity. When you can strike one out, take the guess, and take it quickly. If all four numbers still look alike after fifteen seconds, leave it blank and keep the minute.
These are exam-pattern practice questions built on the chapter's recurring core facts. They are not authenticated year-tagged previous-year papers.
Before You Start
Give yourself 40 minutes for 40 questions.
This is a numbers-and-addresses chapter. Almost nothing here is reasoned out. Every question is a value, a sum, an address or a direction - how many millilitres, which two volumes add up to it, which region of the brain, which way the gradient runs. That has a direct consequence for pacing: most items should take 15 to 25 seconds, and anything that has not come in fifteen seconds is not coming. A number you learnt arrives at once or not at all; staring at four millilitre values will not pull it out. Mark it, move, and come back only if minutes are left over. The exceptions are the arithmetic items - a capacity to be added up, or a volume to be worked back out of a capacity - and those are worth a full minute each, because they are the ones you can be certain about.
Four habits carry this set.
Read the two words that decide every volume question - normal and forcible. They are the whole trap. The volume of air remaining in the lungs after a NORMAL expiration is the functional residual capacity, FRC, that is ERV plus RV. The volume remaining after a FORCIBLE expiration is the residual volume, RV, which averages 1100 mL to 1200 mL. The two are different quantities, both are offered as options, and the only thing separating them in the stem is that one adjective. Underline it before you look at the numbers. The same pair of words sorts tidal volume, which is a normal respiration, from IRV and ERV, which are both forcible.
Write the formula before you reach for the number. Every capacity is a sum, and the sum is safer than the memory. IC = TV + IRV. EC = TV + ERV. FRC = ERV + RV. VC = ERV + TV + IRV. TLC = RV + ERV + TV + IRV, that is VC + RV. If the stem hands you volumes, add them. If it hands you a capacity and asks for a volume, subtract. A calculation item is a free four marks and it does not depend on recall at all.
Answer a gradient question by naming both ends. Diffusion questions are never about the mechanism, they are about direction, and the direction follows from two numbers. Oxygen: 104 mm Hg in the alveoli against 40 mm Hg in the deoxygenated blood, so alveoli to blood; then 95 mm Hg in oxygenated blood against 40 mm Hg in the tissues, so blood to tissues. Carbon dioxide: 45 mm Hg in the tissues against 40 mm Hg in the oxygenated blood, and 45 mm Hg in the deoxygenated blood against 40 mm Hg in the alveoli, so the whole run is tissues to blood to alveoli. Say both ends and the option picks itself.
Keep the addresses in pairs, because the paper swaps them. Larynx is the sound box; epiglottis is the flap that covers the glottis during swallowing. The respiratory rhythm centre is in the medulla; the pneumotaxic centre is in the pons. The conducting part runs to the terminal bronchioles; the exchange part is the alveoli and their ducts. Each of those three pairs is examined as a swap, and a swapped pair is the single commonest way a mark is lost in this chapter while knowing the material perfectly well.