Key concepts in biology revision notes

Key SI Prefixes for Tiny Measurements

Milli (10⁻³), micro (10⁻⁶), nano (10⁻⁹), and pico (10⁻¹²) represent fractional values of a metre. For example, 1 µm = 0.000001 m (micro), and 1 nm = 0.000000001 m (nano). Recognising these allows rapid conversion between units in calculations involving cells.

Standard Form and Unit Conversion

Express values as a × 10ᵇ, with 1 ≤ |a| < 10, for clarity and simplicity. To convert between SI prefixes, use appropriate factors of ten. For example, to go from micrometres to nanometres, multiply by 1000 (since 1 µm = 10⁻⁶ m and 1 nm = 10⁻⁹ m).