Cambridge Medicine Interview

Sketch the relationship between pressure and volume during the cardiac cycle.

Four-phase PV loop: filling (low pressure), isovolumetric contraction (rising pressure, constant volume), ejection (high pressure, falling volume), isovolumetric relaxation. Label each phase as you draw.

A virus has a genome of N base pairs. How many possible distinct genomes of length N exist? What does this tell you about viral evolution?

4^N possible sequences (with 4 nucleotides). Discuss how this combinatorial space drives the speed of viral evolution and the difficulty of designing universal vaccines.

You have a beaker of water at 4°C. What happens to its volume as you cool it further?

Water has anomalous density behaviour — it expands as it cools below 4°C, which is why ice floats. Discuss the hydrogen-bond structure.

A drug has a half-life of 4 hours. After how many half-lives is it effectively cleared from the body?

After ~5 half-lives, ~97% is cleared. Discuss why dosing intervals are set this way and the implications for steady-state plasma concentration.

Why is haemoglobin's oxygen dissociation curve sigmoidal rather than hyperbolic?

Cooperative binding — each O2 bound changes the conformation of the other binding sites. Sketch the curve and explain the physiological advantage at the tissues vs. lungs.

Estimate the volume of blood pumped by the heart in a lifetime.

~5 L/min × 60 min × 24 h × 365 days × 80 years ≈ 200 million litres. State assumptions and round liberally.

Why are women more susceptible to autoimmune disease than men?

Multiple factors: X chromosome (carries many immune-related genes), oestrogen's immune-modulating effects, X-inactivation skewing. Acknowledge uncertainty — this is an active research area.

Walk me through the mechanism of action of a beta-blocker.

Blocks β1 adrenoreceptors → reduces sympathetic stimulation of heart → ↓ heart rate, ↓ contractility, ↓ renin release. Cover clinical uses and contraindications (asthma).

Walk me through what you have done outside of school to test whether medicine is right for you.

Tutors want reflection, not a list. For each experience, articulate what you learned about being a doctor that you couldn't learn from a textbook.

Why Cambridge specifically rather than a London medical school?

Reference the integrated BSc (the "Tripos" year), the supervision system, the strong basic-science focus in the first three years. Avoid prestige answers.

Here is a graph showing antibody concentration over time after a primary and secondary exposure to an antigen. Explain the differences.

Secondary response: faster, higher magnitude, longer-lasting, IgG-dominated. Discuss memory B cells and class switching.

Why do we shiver when we're cold?

Skeletal muscle contractions generate heat (~5× resting metabolic rate). Discuss the hypothalamic temperature setpoint and the autonomic response chain.

A patient has a sodium of 120 mmol/L. What does that mean and what could cause it?

Hyponatraemia. Differentiate hypovolaemic (D&V, diuretics), euvolaemic (SIADH), hypervolaemic (heart failure, cirrhosis). Discuss why correcting too quickly is dangerous (central pontine myelinolysis).

Explain the concept of natural selection to me as if I had never studied biology.

Use a concrete example (e.g. moths during industrial revolution, antibiotic resistance). Avoid jargon. Check understanding mid-explanation.

Why does a tennis ball bounce lower with each bounce?

Energy lost to heat, sound, deformation. Discuss coefficient of restitution. Cambridge will sometimes test physics-style reasoning even on biological topics.

Here's an ECG. What can you tell me about it?

You're not expected to diagnose. Describe what you can see systematically: rate, rhythm, intervals (PR, QRS, QT), waveform morphology.