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
“Enzymes are molecular matchmakers — they let reactions happen in seconds that would otherwise take years.”
A frequent error is thinking every protein is an enzyme. In reality, polymers of amino acids that build tissues, act as enzymes, and transport molecules.
Memory trick: all enzymes are proteins (mostly), but not all proteins are enzymes.
“Enzymes are molecular matchmakers — they let reactions happen in seconds that would otherwise take years.”
Sugars and their polymers — the cell's quick energy source and structural material (cellulose).
Memory trick: starch stores energy in plants, glycogen in animals, cellulose gives structure.
“Enzymes are molecular matchmakers — they let reactions happen in seconds that would otherwise take years.”
A frequent error is confusing starch (plant storage) with glycogen (animal storage). In reality, sugars and their polymers — the cell's quick energy source and structural material (cellulose).
Memory trick: starch stores energy in plants, glycogen in animals, cellulose gives structure.
“Enzymes are molecular matchmakers — they let reactions happen in seconds that would otherwise take years.”
DNA and RNA, the molecules that store and carry genetic information.
Memory trick: DNA is the master copy; RNA is the working message.
“Enzymes are molecular matchmakers — they let reactions happen in seconds that would otherwise take years.”
A frequent error is thinking RNA cannot store genetic information (some viruses use RNA). In reality, DNA and RNA, the molecules that store and carry genetic information.
Memory trick: DNA is the master copy; RNA is the working message.
“Enzymes are molecular matchmakers — they let reactions happen in seconds that would otherwise take years.”
A competitive inhibitor blocks the active site and can be overcome by more substrate; a non-competitive inhibitor binds elsewhere and cannot.
“Enzymes are molecular matchmakers — they let reactions happen in seconds that would otherwise take years.”
Saturated fats have no C=C double bonds and are usually solid; unsaturated fats have double bonds and are usually liquid oils.
“Enzymes are molecular matchmakers — they let reactions happen in seconds that would otherwise take years.”
Enzymes are catalysts — they are released unchanged and reused many times.
“A single fertilised cell divides into you — with the DNA copied almost perfectly each time.”
G1 (growth), S (DNA replication), G2 (growth) make up interphase, followed by M phase (division).
Memory trick: DNA replicates in S phase, well before mitosis begins.
“A single fertilised cell divides into you — with the DNA copied almost perfectly each time.”
A frequent error is thinking DNA is copied during mitosis. In reality, G1 (growth), S (DNA replication), G2 (growth) make up interphase, followed by M phase (division).
Memory trick: DNA replicates in S phase, well before mitosis begins.
“A single fertilised cell divides into you — with the DNA copied almost perfectly each time.”
A frequent error is expecting variation from mitosis. In reality, division that produces two genetically identical diploid daughter cells for growth and repair.
Memory trick: mitosis = identical copies; think 'maintenance'.
“A single fertilised cell divides into you — with the DNA copied almost perfectly each time.”
A frequent error is thinking meiosis gives identical cells like mitosis. In reality, reductional division producing four genetically different haploid gametes.
Memory trick: meiosis halves the chromosome number and shuffles genes.
“A single fertilised cell divides into you — with the DNA copied almost perfectly each time.”
A frequent error is thinking crossing over happens in mitosis. In reality, the exchange of segments between homologous chromosomes during meiosis, creating variation.
Memory trick: crossing over (in meiosis I) is a key source of genetic diversity.
“A single fertilised cell divides into you — with the DNA copied almost perfectly each time.”
Mitosis gives 2 identical diploid cells (growth/repair); meiosis gives 4 varied haploid cells (gametes).
“A single fertilised cell divides into you — with the DNA copied almost perfectly each time.”
Haploid (n) cells have one set of chromosomes (gametes); diploid (2n) cells have two sets (body cells).
“A single fertilised cell divides into you — with the DNA copied almost perfectly each time.”
A chromatid is one half of a duplicated chromosome; the two sister chromatids joined at the centromere form one chromosome.
“A single fertilised cell divides into you — with the DNA copied almost perfectly each time.”
DNA replication happens in the S phase of interphase, before mitosis — not during it.
“Every breath you take was 'made' by a plant splitting water in sunlight.”
Occur in the thylakoid membranes, using light to make ATP and NADPH and releasing O₂ by splitting water.
Memory trick: the O₂ you breathe from plants comes from splitting WATER (photolysis).
“Every breath you take was 'made' by a plant splitting water in sunlight.”
A frequent error is thinking the released oxygen comes from carbon dioxide. In reality, occur in the thylakoid membranes, using light to make ATP and NADPH and releasing O₂ by splitting water.
Memory trick: the O₂ you breathe from plants comes from splitting WATER (photolysis).
“Every breath you take was 'made' by a plant splitting water in sunlight.”
Occurs in the stroma, fixing CO₂ into sugar using the ATP and NADPH from the light reactions.
Memory trick: it's called light-independent, but it usually runs in daylight using the light reaction's products.
“Every breath you take was 'made' by a plant splitting water in sunlight.”
A frequent error is thinking the 'dark reaction' happens only at night. In reality, occurs in the stroma, fixing CO₂ into sugar using the ATP and NADPH from the light reactions.
Memory trick: it's called light-independent, but it usually runs in daylight using the light reaction's products.
“Every breath you take was 'made' by a plant splitting water in sunlight.”
The green pigment that absorbs mainly red and blue light and reflects green.
Memory trick: leaves look green precisely because they REFLECT green light.
“Every breath you take was 'made' by a plant splitting water in sunlight.”
A frequent error is thinking plants absorb green light for photosynthesis. In reality, the green pigment that absorbs mainly red and blue light and reflects green.
Memory trick: leaves look green precisely because they REFLECT green light.
“Every breath you take was 'made' by a plant splitting water in sunlight.”
The light reaction (thylakoid) needs light and makes ATP/NADPH + O₂; the dark reaction (stroma) fixes CO₂ into sugar using those products.