xylem parenchyma cell collencyma cell straited muscle
(i) Xylem
- Made up of vessels and tracheid
- Consist of dead cells
- Allows unobstructed passage of water and mineral salts
- Has pits which permits horizontal transport
- Narrow lumen to improve capillarity
- Tapering ends overlap, giving additional mechanical strength
- Long and tubular vessels, good conducting structures
- Mark points annotated diagram
(ii) Parenchyma
- Made up of living cells involved in food storage
- Has a large sap vacuole, gives turgidity for support
- Irregular in shape as packing tissue
- Has thin cellular cell wall, pathway for water and mineral ions
- Elongated and flattened cell offer protection from desiccation and infection
- Plasmodesmata between adjacent cells, allow lateral transport between cells (1 x 5 = 5 marks)
(iii) Collenchyma
- Made up of living cells; covering outer region of cortex, midrib of leaves
- Elongated and polygonal cells
- Tapering end; give mechanical support
- Cell wall of cellulose; additional mechanical support (1 x 3 = 3 marks)
(iv) striated muscle
- Numerous muscle fibres; thin myofibers; long, cylindrical with alternate light and dark bands/actin and myosin contract and relax; voluntary movement.
- Oval nuclei at surface of each fibre; control cell activity
- Numerous mitochondria interposed between muscle filament; presence of glycogen; provide energy for muscular action
- Presence of vesicles triad involved in the uptake and release of Ca24 ions
- Fibres enclosed in sarcolemma; each has several motor neurons attached to its sheath; conduction of impulse; causes contraction of fibre
- Bundles of fibres enclosed by collagen fibres and connective tissues; from tendons at the ends of muscles attach muscles to skeletal elements (1 x 6 = 6 marks) (total = 20 marks)
