organisation+ specialisation of cells

• different cells within an organism are specialised for different roles and organised into efficient biological structures, each with a particular function.
• cells within a multicellular organism are differentiated= they are specialised to carry out specific functions.
• erythrocytes 


  -have flattened biconcave shape, which increases their SA:V. It's essential to their role in transporting oxygen. Have no nuclei which increases space available for oxygen+ haemoglobin. Flexible so they can squeeze through narrow capillaries.
• Neutrophils 


  =role in immune system. Have a multi-lobed nucleus so is easier to squeeze through small gaps. Granular cytoplasm contains many lysosomes that contain enzymes used to attack pathogens.
• sperm cells 


  = function to deliver genetic material to egg cell. Have a tail/flagellum for movement. Contain many mitochondria to supply energy needed to swim. Acrosome on head of sperm contains digestive enzymes which digest protective layers around ovum.
• palisade cells 


  = in mesophyll, contains chloroplasts to absorb large amounts of light for photosynthesis. Rectangular box shaped which can be packed to form a continuous layer. Thin walls, increasing rate of diffusion of co2. Large vacuole to maintain turgor pressure. Chloroplasts move in cytoplasm to absorb more light.
• root hair cell

  =surfaces of root near tips, have long extensions which increase the SA of cells. This maximises the uptake of water and minerals from the soil.
• guard cells 


  = on surfaces of leaves form small opening called stomata. For co2 to enter for photosynthesis. When they lose water and become less swollen they change shape and stomata closes to stop more water loss. Cell wall is thicker on 1 side so cell doesn't change shape symmetrically as volume changes.
• tissues

  = made up of a collection of differentiated cells that have a specialised function. Each tissue is adapted for a particular function.

  • nervous= adapted to support transmission of electrical impulses.
  • epithelial= adapted to cover body surfaces, internal and external.
  • muscle= adapted to contract.
  • connective= adapted to hold tissue together or as transport medium.
• squamous epithelium 


  = flat appearance, very thin due to squat or flat cells that are only 1 cell thick. Present when rapid diffusion across a surface. It forms the lining of the lungs and allows rapid diffusion of oxygen into the blood.
• cartilage 


  = connective tissue found in ear, nose. Contains fibres of the proteins elastin and collagen. Firm, flexible tissue composed of chondrocyte cells embedded in an extracellular matrix. Prevents ends of bones from rubbing together and causing damage.
• muscle 


  = needs to be able to shorten in length in order to move bones. Types of muscle fibres; skeletal contain myofibrils which contain contractile proteins.
• epidermis 


  = single layer of closely packed cells covering surfaces of plants. Covered by waxy, waterproof cuticle to reduce water loss. Stomata present in epidermis.
• xylem tissue

  = transport of water and minerals. Made of elongated dead cells. Walls strengthened with waterproof material= lignin.
• phloem tissue

  = transport of nutrients. Composed of columns of sieve tube cells separated by perforated walls called sieve plates.