Specialised cells

5. Thin, flat cells forming a single layer in alveoli and capillaries, reducing diffusion distance for rapid gas exchange (9,10,5)
8. Structural feature that increases the rate of absorption in root hair cells (5,7)
10. Organelles containing chlorophyll that absorb light energy for photosynthesis in palisade cells (12)
12. Organelles containing hydrolytic enzymes for digesting pathogens during phagocytosis (10)
13. Motile structure that propels sperm cells towards the egg (9)
14. Cells with a flagellum, many mitochondria and an acrosome, adapted for movement towards and penetration of the egg (5,5)
15. Plant cells with long extensions and thin walls, increasing surface area for water absorption by osmosis and mineral ion uptake by active transport (4,4,5)

1. Paired epidermal cells with unevenly thickened walls that change shape when turgid or flaccid to regulate gas exchange and water loss (5,5)
2. Shape that increases surface area to volume ratio and shortens diffusion distance in red blood cells (9)
3. Elongated leaf cells packed with chloroplasts near the upper surface, maximising light absorption and reducing diffusion distance for carbon dioxide (8,9,5)
4. White blood cells with a multi lobed nucleus and many lysosomes, enabling movement through capillary walls and phagocytosis of pathogens (11)
6. Nuclear structure allowing neutrophils to squeeze through capillary walls during diapedesis (4,5)
7. Red blood cells with a biconcave shape and no nucleus, maximising surface area and space for haemoglobin in oxygen transport (12)
9. Structural feature that provides more space for haemoglobin in erythrocytes (2,7)
11. Cells lining the airways with surface cilia whose coordinated beating moves mucus and trapped pathogens (7,10,5)