IP Biology Upper Sec 05: Transport 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

• Double circulation: pulmonary (heart–lungs–heart) and systemic (heart–body–heart). Arteries thick, elastic, small lumen; veins thinner with valves; capillaries one-cell-thick, large total area.
• Blood components: RBC biconcave, no nucleus, haemoglobin for O₂ transport; plasma carries nutrients, hormones, waste, CO₂; WBC (phagocytes ingest, lymphocytes make antibodies); platelets + clotting factors form fibrin mesh.
• Heart anatomy: atria/ventricles, valves; cardiac cycle systole/diastole; path of blood through heart and lungs.
• Coronary heart disease: fatty deposits narrow arteries; risk factors (diet high in saturated fat, smoking, lack of exercise, stress); prevention (diet, exercise, no smoking, statins, angioplasty/bypass).
• ABO blood groups: antigens on RBC, antibodies in plasma; compatibility rules to avoid agglutination.

Detailed notes

• Plasma transports glucose, amino acids, hormones, urea, $\ce{CO2}$