SBI4U – Grade 12 Biology Complete Review Sheet
Use this sheet for fast revision, definitions, processes, and exam-ready facts.
UNIT 1: BIOCHEMISTRY
1 Macromolecules: carbohydrates (energy), lipids (long-term energy, membranes), proteins (structure & enzymes),
nucleic acids (DNA/RNA).
2 Functional groups: hydroxyl (polar), carbonyl (polarity), carboxyl (− charge), amino (+ charge), phosphate (energy
transfer), sulfhydryl (disulfide bonds).
3 Enzymes: biological catalysts that lower activation energy by forming enzyme–substrate complexes.
4 Factors affecting enzymes: temperature, pH, substrate concentration, inhibitors.
5 Competitive inhibitors block active site; non-competitive change enzyme shape.
6 Metabolism = sum of all chemical reactions in the cell.
UNIT 2: METABOLIC PROCESSES
1 Cellular respiration equation: C■H■■O■ + 6O■ → 6CO■ + 6H■O + ATP.
2 Stages: glycolysis (cytoplasm), Krebs cycle (matrix), electron transport chain (inner membrane).
3 ATP is the energy currency of the cell.
4 Photosynthesis equation: 6CO■ + 6H■O + light → C■H■■O■ + 6O■.
5 Light reactions occur in thylakoids; Calvin cycle occurs in stroma.
6 Anaerobic respiration = fermentation (lactic acid or alcohol).
UNIT 3: MOLECULAR GENETICS
1 DNA structure: double helix, antiparallel strands, complementary base pairing (A–T, C–G).
2 Replication is semi-conservative and occurs in S-phase.
3 Transcription: DNA → mRNA (nucleus).
4 Translation: mRNA → protein (ribosome).
5 Mutations: point, frameshift; can be silent, missense, or nonsense.
6 Gene expression is regulated by promoters, repressors, and transcription factors.
UNIT 4: HOMEOSTASIS
1 Homeostasis maintains internal balance using negative feedback.
2 Nervous system uses electrical signals; endocrine system uses hormones.
3 Insulin lowers blood glucose; glucagon raises it.
4 Kidneys regulate water, ions, and waste via nephrons.
5 Thermoregulation involves sweating, shivering, vasodilation, vasoconstriction.
6 Positive feedback amplifies change (rare, e.g., childbirth).
UNIT 5: POPULATION DYNAMICS
Use this sheet for fast revision, definitions, processes, and exam-ready facts.
UNIT 1: BIOCHEMISTRY
1 Macromolecules: carbohydrates (energy), lipids (long-term energy, membranes), proteins (structure & enzymes),
nucleic acids (DNA/RNA).
2 Functional groups: hydroxyl (polar), carbonyl (polarity), carboxyl (− charge), amino (+ charge), phosphate (energy
transfer), sulfhydryl (disulfide bonds).
3 Enzymes: biological catalysts that lower activation energy by forming enzyme–substrate complexes.
4 Factors affecting enzymes: temperature, pH, substrate concentration, inhibitors.
5 Competitive inhibitors block active site; non-competitive change enzyme shape.
6 Metabolism = sum of all chemical reactions in the cell.
UNIT 2: METABOLIC PROCESSES
1 Cellular respiration equation: C■H■■O■ + 6O■ → 6CO■ + 6H■O + ATP.
2 Stages: glycolysis (cytoplasm), Krebs cycle (matrix), electron transport chain (inner membrane).
3 ATP is the energy currency of the cell.
4 Photosynthesis equation: 6CO■ + 6H■O + light → C■H■■O■ + 6O■.
5 Light reactions occur in thylakoids; Calvin cycle occurs in stroma.
6 Anaerobic respiration = fermentation (lactic acid or alcohol).
UNIT 3: MOLECULAR GENETICS
1 DNA structure: double helix, antiparallel strands, complementary base pairing (A–T, C–G).
2 Replication is semi-conservative and occurs in S-phase.
3 Transcription: DNA → mRNA (nucleus).
4 Translation: mRNA → protein (ribosome).
5 Mutations: point, frameshift; can be silent, missense, or nonsense.
6 Gene expression is regulated by promoters, repressors, and transcription factors.
UNIT 4: HOMEOSTASIS
1 Homeostasis maintains internal balance using negative feedback.
2 Nervous system uses electrical signals; endocrine system uses hormones.
3 Insulin lowers blood glucose; glucagon raises it.
4 Kidneys regulate water, ions, and waste via nephrons.
5 Thermoregulation involves sweating, shivering, vasodilation, vasoconstriction.
6 Positive feedback amplifies change (rare, e.g., childbirth).
UNIT 5: POPULATION DYNAMICS
