IP Biology Upper Sec 06: Respiration in Humans

These notes align with SEAB GCE O-Level Biology (6093) content used in IP programmes (exams from 2026).

Status: SEAB O-Level Biology 6093 syllabus (exams from 2026) checked 2025-11-30 - scope unchanged; remains the reference for this note.

What you must know

• Gas exchange system: nasal cavity, larynx, trachea (C-shaped cartilage), bronchi, bronchioles, alveoli; breathing via diaphragm and external/internal intercostal muscles.
• Alveoli: numerous (large area), one-cell-thick walls, moist lining, dense capillary network, elastic fibres for recoil.
• Aerobic respiration: $\ce{glucose + oxygen -> carbon\ dioxide + water + energy}$