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
“Three scientists across decades pieced together that life's common brick is the cell.”
All living things are made of cells, and every cell comes from a pre-existing cell.
Memory trick: Cells come only from cells.
“Bacteria are studio flats; your cells are mansions with many rooms.”
Prokaryotes (bacteria) lack a true nucleus and organelles; eukaryotes (plants, animals) have both.
Memory trick: Pro = 'before' the nucleus.
“These ancient guest-microbes now power almost every cell in your body.”
The powerhouse of the cell, where aerobic respiration makes most ATP; it has its own DNA.
Memory trick: Powerhouse of the cell.
“Green kitchens that cook sugar out of sunlight.”
The organelle where photosynthesis happens in plant cells.
Memory trick: Site of photosynthesis.
“The cell's 3-D printers, churning out proteins from genetic blueprints.”
A non-membrane structure that builds proteins.
Memory trick: Protein factory.
“A smart security gate deciding who gets in and out.”
A selectively permeable boundary (fluid-mosaic model) controlling what enters and leaves.
Memory trick: Selectively permeable.
“The cell's head office, storing the master instructions.”
The control centre holding the cell's DNA.
Memory trick: Holds DNA; runs the cell.
“Plants wear rigid armour (cell wall); animal cells stay flexible.”
Plant cells have a cell wall, chloroplasts and a large vacuole; animal cells don't (but have centrioles).
Memory trick: Wall + chloroplast = plant.
“They make reactions that would take years happen in a heartbeat.”
Biological catalysts that speed reactions by lowering activation energy and are reused.
Memory trick: Catalysts — not used up.
“One key, one lock — that precision keeps cell chemistry orderly.”
Each enzyme fits its specific substrate like a lock and key.
Memory trick: Active site = shape-specific.
“A fever that runs too hot can denature the very enzymes that keep you alive.”
Enzyme activity depends on temperature and pH, each with an optimum.
Memory trick: Too hot / wrong pH → denature.
“DNA is the master library; RNA is the working photocopy.”
DNA is double-stranded (deoxyribose, thymine) and stores genes; RNA is single-stranded (ribose, uracil) and expresses them.
Memory trick: DNA stores; RNA works.
“Most of a cell's life is spent quietly growing and copying, not dividing.”
Interphase (G1, S, G2) then M phase; DNA is copied in S phase.
Memory trick: DNA copies in S, before mitosis.
“Every time a wound heals, mitosis is rebuilding you cell by cell.”
Division making two genetically identical diploid cells for growth and repair.
Memory trick: Identical copies.
“Meiosis is why no two siblings (except identical twins) are the same.”
Reductional division making four genetically varied haploid gametes.
Memory trick: Halves chromosomes; shuffles genes.
“Genes get shuffled like cards, dealing each gamete a unique hand.”
Exchange of segments between homologous chromosomes in meiosis, creating variation.
Memory trick: Source of genetic variety.
“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.