This topic summary covers Knowledge Organiser within Blood Components and Vessels for GCSE Biology. Blood composition, red and white blood cells, platelets, plasma, blood vessel structure and function, adaptations for transport It is section 14 of 16 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 14 of 16
Practice
18 questions
Recall
24 flashcards
Knowledge Organiser
Key Terms
- Plasma — liquid component (90% water)
- Erythrocyte — red blood cell
- Leucocyte — white blood cell
- Haemoglobin — oxygen-carrying protein
- Phagocytosis — engulfing pathogens
- Platelet — clotting cell fragment
- Fibrinogen — clotting protein in plasma
- Fibrin — insoluble clot mesh
- Lumen — central space inside a vessel
Must-Know Facts
- Blood is 55% plasma, 45% cells
- Red cells: biconcave, no nucleus, packed with haemoglobin
- Phagocytes engulf; lymphocytes produce antibodies
- Platelets are cell fragments, not whole cells
- Arteries: thick wall, small lumen, no valves
- Veins: thin wall, large lumen, valves present
- Capillaries: one cell thick, tiny lumen, branching network
- Clotting sequence: damage → platelet plug → fibrin mesh
Common Marks Lost
- Saying "blue blood" — deoxygenated blood is dark red
- Confusing artery/vein in pulmonary circulation
- Describing phagocytosis as "eating" without using the term
- Saying platelets are cells — they are cell fragments
- Stating adaptations without explaining the function link