module 2 (specialised cells)

• Erythrocyte (red blood cell)

  • Biconcave shape to increase surface area for diffusion and increase cell flexibility, no nucleus to maximise oxygen-carrying capacity, made from stem cells in the bone marrow
• Neutrophils


  • Type of white blood cell, have a lobed nucleus and granular cytoplasm, flexible to surround pathogens and engulf them, contain lysosomes filled with the hydrolytic enzyme, lysozyme
• Sperm cells


  • Flagellum contains many mitochondria to release energy for locomotion, acrosome in the head contains digestive enzymes to digest the wall of the egg cell
• Palisade cells


  • Located in the mesophyll tissue layer of leaves, rectangular, tightly packed cells that contain many chloroplasts to absorb and maximise light energy for photosynthesis, have thin cell walls to reduce the diffusion distance of carbon dioxide
• Root hair cells


  • Cells on the surface of roots, long projections to increase surface area for osmosis of water and active transport of mineral ions, thin cell wall to reduce the diffusion distance
• Guard cells


  • Pair of cells with flexible walls, more so on one side, which results in the cells bending when turgid to open stomata and closing when flaccid, helps control water loss by transpiration
• Squamous epithelial cells


  • Usually only a single layer of flat cells in contact with the basement membrane of epithelium, provides a short diffusion distance
• Ciliated epithelial cells


  • Have hair-like projections that say to move substances, such as mucus, out of the lungs, or an egg in the oviduct, goblet cells also located within the epithelium and release mucus to trap molecules
• Cartilage


  • Firm and flexible connective tissue, located in the outer ear, nose and the end of bones, provides structural support and prevents bones from rubbing together, made up of collagen and elastin fibres, and chondrocyte cells within an extracellular matrix
• Muscle


  • Composed of tissues that can contract and relax to create movement, muscles have multiple fibres connecting with connective tissues in between
• Xylem


  • Part of the vascular bundle in plants responsible for transporting water and mineral ions, made up of elongated, hollow dead cells, with lignin in the walls to strengthen and waterproof
• Phloem


  • Part of the vascular bundle, transports organic substances made in photosynthesis, made of sieve tube element cells and companion cells
• Sieve tube elements


  • Cells have perforated end walls, lacking most organelles to make the transport of sugars easier