Fundamentals
The core facts every aspirant should own — each a titled nugget with a real-world story, the concept in plain words, and a memory trick. Works even when the internet doesn't.
300 fundamentals
“Every calorie you eat traces back to a plant catching sunlight.”
Plants convert CO₂ and water into glucose and O₂ using light energy in chloroplasts.
6CO₂+6H₂O→C₆H₁₂O₆+6O₂
Memory trick: Light → sugar + oxygen.
“The light stage charges the batteries; the dark stage spends them building sugar.”
Light reactions (thylakoid) make ATP/NADPH and O₂; the Calvin cycle (stroma) fixes CO₂ into sugar.
Memory trick: Light: energy; dark: sugar.
“Every breath of oxygen was pried out of a water molecule by sunlight.”
The oxygen released comes from splitting water, not from CO₂.
Memory trick: O₂ comes from water.
“Leaves look green precisely because they reject green light.”
Chlorophyll absorbs mainly red and blue light and reflects green.
Memory trick: Green is reflected, not used.
“Trees are giant straws, and transpiration is the suck that lifts water 100 m up.”
Loss of water vapour from leaves that pulls water up from the roots.
Memory trick: Leaf water loss pulls the column up.
“Respiration cashes in the sugar cheque photosynthesis wrote.”
Cells release energy from glucose; glycolysis (cytoplasm) then aerobic stages (mitochondria).
Memory trick: Glucose + O₂ → energy + CO₂ + H₂O.
“Sprint too hard and your muscles switch to anaerobic, piling up lactic acid.”
Aerobic (with O₂) yields ~36–38 ATP; anaerobic (fermentation) yields only ~2.
Memory trick: Oxygen → far more energy.
“Chewing bread long enough turns it sweet as salivary amylase frees the sugars.”
Amylase digests starch, pepsin/trypsin digest protein, lipase digests fat — each in its region.
Memory trick: Different enzymes, different foods.
“Unfolded, your intestinal lining could cover a tennis court.”
Most nutrients are absorbed through villi, which hugely increase surface area.
Memory trick: Villi = surface for absorption.
“Bile is dish-soap for fat, breaking it up so enzymes can attack.”
Bile (from the liver) emulsifies fats into droplets; it contains no enzymes.
Memory trick: Emulsifier, not enzyme.
“Your lungs hold ~300 million alveoli — a huge surface for trading gases.”
O₂ and CO₂ swap by diffusion across thin, moist alveolar walls.
Memory trick: Diffusion across thin walls.
“Haemoglobin is a molecular bus, seating four oxygen passengers at a time.”
Most oxygen is carried by haemoglobin in red blood cells.
Memory trick: Hb carries O₂.
“Two loops keep clean and dirty blood from mixing, unlike a fish's single loop.”
Blood passes through the heart twice per circuit — to the lungs and to the body.
Memory trick: Pulmonary + systemic loops.
“A tireless double-pump beating ~100,000 times a day.”
Two atria receive blood; two ventricles pump it — left side oxygenated, right deoxygenated.
Memory trick: Left = oxygenated.
“The pulmonary artery is the odd one out — an artery carrying deoxygenated blood.”
Arteries carry blood away from the heart at high pressure; veins return it with valves.
Memory trick: Arteries: away; veins: toward.
“About a million nephrons per kidney clean your entire blood volume many times a day.”
The kidney's filtering unit — ultrafiltration then selective reabsorption.
Memory trick: Filter, then reabsorb the good stuff.
“The liver converts poisonous ammonia into safer urea for disposal.”
Humans excrete nitrogen mainly as urea, which is less toxic than ammonia.
Memory trick: Urea = our nitrogen waste.
“Your brain wires ~86 billion of these into the most complex network known.”
The nerve cell that carries impulses via dendrites (in), an axon (out) and synapses.
Memory trick: Dendrites in, axon out.
“Thoughts are sparks that leap gaps using chemical messengers.”
Electrical within a neuron; chemical (neurotransmitter) across a synapse.
Memory trick: Within = electric; across = chemical.
“You drop a hot pan before your brain even registers the pain.”
A fast, involuntary response routed through the spinal cord, bypassing the brain.
Memory trick: Spinal shortcut for speed.
“A drop of hormone can change your whole body's behaviour.”
Chemical messengers from ductless (endocrine) glands, carried by blood to target organs.
Memory trick: Endocrine = ductless, into blood.
“This pancreatic tug-of-war keeps your blood sugar in a safe band.”
Insulin lowers blood glucose (storage); glucagon raises it — they are antagonists.
Memory trick: Insulin puts glucose IN.
“A monk counting peas discovered the hidden rules of heredity.”
Dominance, segregation and independent assortment govern how traits pass on.
Memory trick: Alleles segregate cleanly.
“Two tall plants can hide different genetic recipes inside.”
Genotype is the genetic makeup (Tt); phenotype is the visible trait (tall).
Memory trick: Genes vs appearance.