Bio cell

• Cell membrane


  Also known as plasma membrane or plasmalemma
• Cell membrane


  • It is the outer covering that encloses the cell contents and regulates the movement of materials in and out of the cell
  • It is made of a double layer (bilayer) of phospholipids with proteins embedded in or attached to the phospholipids
  • It is selectively permeable or semi-permeable as it allows some types of molecules to pass through it and not others
  • It is flexible
• Mitochondria


  • Sausage-shaped organelles
  • They are the sites for respiratory reactions that yield energy for the cell
• Mitochondria


  • They are bound to two cell membranes: the inner membrane is greatly folded into cristae to increase the surface area for attachment of respiratory enzymes, and the outer membrane
  • The arrangement and number of mitochondria in a cell depends on the cell's energy requirements - cells which require larger amounts of energy contain many mitochondria
• Cell specialization

  Newly found cells undergo structural modification so as to perform specific functions
• Specialized cells


  • They are suited to perform specific functions
• Root hair


  Extension (projection) of the root epidermal cell that increases the surface area for absorption of water and mineral salts from the soil
• Guard cells

  • Bean shaped, contain chloroplasts, have thick inner walls and thin outer walls
  • Enable them to control the opening and closing of stomata to allow for gaseous exchange
• Palisade cell.

  • Contain chloroplasts that trap light energy for photosynthesis
  • Closely packed.
  • They are the main photosynthetic cells which are found beneath the upper epidermis of the leaf
• Nerve cells


  • Structural and functional unit of the nervous system
  • Have extensions called axons and dendrites that facilitate pulse transmission
• Sperm cell


  • Long tail-like extension for propulsion
  • Numerous mitochondria to provide energy for propulsion
  • Acrosome that contains lytic enzymes to digest egg membranes
• Red blood cells


  • Biconcave in shape
  • Lack a nucleus
  • Contain haemoglobin
  • Enable them to transport oxygen within the body
• White blood cells


  • Have large nuclei
  • Some can change shape and exhibit amoeboid movement
  • Protect the body against infections by destroying disease-causing microorganisms through antibody production or phagocytosis
• Muscle cells


  • Contain contractile fibrils that contract and relax to bring about movement
• Tissue


  A collection of cells of similar type that are specialized to perform the same function
• Tissues are groups of cells that have come together to perform a specific function