Biology – Core Concepts
Cell types
Animal · Plant
Bacterial
Photosynthesis
CO₂ + H₂O → glucose + O₂
Light needed
Aerobic resp.
glucose + O₂ → CO₂ + H₂O + energy
Genetics
DNA → Gene → Chromosome
23 pairs in humans
- Mitochondria = powerhouse (ATP production by aerobic respiration)
- Chloroplast only in plant cells; contains chlorophyll (green pigment)
- Cell wall (plant) = cellulose; not the same as a cell membrane
- Diffusion = high → low concentration; NO energy needed (passive)
- Osmosis = water through semi-permeable membrane; high water potential → low
- Dominant allele always expressed; recessive only when homozygous (bb)
Worked Example
Q: A plant is placed in a dark cupboard for 24 hours. Which substance runs out first?
A: Carbon dioxide is already in the air, but without light, photosynthesis stops so the plant's glucose stores decrease. Answer: glucose.
Chemistry – Core Concepts
Atom parts
Proton (+) nucleus
Neutron (0) nucleus
Electron (-) shells
Periodic Table
Groups = columns
Periods = rows
Group 1 = alkali metals
Reaction types
Combustion · Oxidation
Neutralisation
Decomposition
pH scale
0–6 = acid
7 = neutral
8–14 = alkali
- Atomic number = number of protons (= electrons in neutral atom)
- Mass number = protons + neutrons
- Isotopes = same element, different number of neutrons
- Metal + acid → salt + hydrogen gas (fizzing)
- Acid + alkali → salt + water (neutralisation)
- Exothermic = releases heat (combustion); Endothermic = absorbs heat (thermal decomp.)
Worked Example
Q: An atom has 11 protons, 11 electrons and 12 neutrons. What is its mass number?
A: Mass number = protons + neutrons = 11 + 12 = 23. This is sodium-23.
Physics – Core Concepts
Speed formula
speed = distance ÷ time
v = d / t (m/s)
Forces
Newton's 1st: constant velocity if balanced
F = m × a
Energy
KE = ½mv²
GPE = mgh
Conserved always
EM Spectrum
Radio → Micro → IR → Visible → UV → X-ray → Gamma
- Current (A) = flow of charge; Voltage (V) = energy per charge; V = I × R
- Series circuit: same current everywhere; Parallel: same voltage across each branch
- Light travels at 3×10⁸ m/s; faster in vacuum than any medium
- Sound needs a medium (cannot travel in a vacuum)
- Density = mass ÷ volume (kg/m³); floats if less dense than the fluid
Worked Example
Q: A car travels 150 m in 5 s. What is its speed?
A: speed = distance ÷ time = 150 ÷ 5 = 30 m/s