Biology and Life Processes
Cells and transport
Know the shared features of cells - cell membrane, cytoplasm, nucleus, mitochondria, ribosomes - and the plant extras: cell wall, chloroplasts, permanent vacuole. Root cells have no chloroplasts. Substances move by diffusion (high to low concentration, no energy), osmosis (water across a partially permeable membrane from dilute to concentrated solution) and active transport (against the gradient, requiring energy).
Enzymes and biochemistry
Enzymes are protein catalysts with a specific active site; heat or extreme pH denatures them by changing the shape of that site. Learn both equations: photosynthesis (carbon dioxide + water → glucose + oxygen, requiring light and chlorophyll) and aerobic respiration (glucose + oxygen → carbon dioxide + water, releasing energy). Plants respire continuously, day and night.
Systems and homeostasis
Link structure to function: alveoli and villi for surface area, xylem for water and phloem for sugars, red blood cells for oxygen transport, nephrons for filtration. Homeostasis keeps conditions steady through negative feedback involving nerves and hormones.
Genetics and ecology
DNA carries genes; alleles may be dominant or recessive. Energy flows one way through food chains (roughly 10% transfers to the next level) while nutrients cycle; arrows show the direction of energy flow, not "what eats what".
Traps
Confusing respiration with photosynthesis; thinking osmosis moves solute; forgetting plants respire; muddling diffusion with active transport; reversing food-chain arrows; mixing magnification units.
Worked example
Two heterozygous parents (Aa × Aa) give genotype ratio 1 AA : 2 Aa : 1 aa, so the phenotype ratio is 3 dominant : 1 recessive.