The organisation and specialisation of cells

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• 2. Present in mesophyll. Contain chloroplasts (able to move) - absorbs light for photosynthesis. Rectangular box shapes, closely packed - continuous layer. Thin cell walls, increased rate of diffusion of CO2. Large vacuole - maintain turgor pressure. (5, 8, 5)
• 3. Essential role in immune system. Characteristic multi-lobed nucleus which makes it easier for them to squeeze through small gaps to get to site of infection. Granular cytoplasm contains lysosomes that contain enzymes used to attack pathogens. (6, 11)
• 4. Male gametes. Deliver genetic information to female gamete, the ovum. Tail/ flagellum - capable of movement, contain many mitochondria to supply energy. Acrosome on head releases digestive enzymes - digest protective layers, allows sperm to penetrate (6, 5, 5)
• 5. Single layer of closely packed cells covering surafe of plants. Usually covered by waxy, waterproof cuticle- prevents water loss. Stomata (pair of guard cells) are present in epidermis. Allow CO2 in and out and water vapour and oxygen in and out. (5, 6, 9)
• 6. Flattened, biconcave - increases their SA to V ratio. This is essential to their role of transporting oxygen around the body. They do not have a nuclei or many other organelles - increases space for haemoglobin. Flexible to travel through capillaries (6, 12)
• 7. Needs to shorten in length to be able to move bones. Skeletal muscle fibres (attached to bones) contain myofibrils which contain contractile proteins. Individual fibres can be seperated by connective tissue. (6, 6, 6)