Cells

• Body hierarchy:

  • Cell: the basic building block of all living things
  • Tissue: a group of similar cells which together perform a particular function
  • Organ: composed of various tissues which together carry out one or more major functions in an organism
  • System: a group of organs which together carry out major functions within the body
• Structure of a cell: cell membrane, cytoplasm, organelles, cytosol, cytoskeleton, inclusions

  
• Functions of a cell: metabolism (chemical reactions), reproduction, movement, communication with other cells
• Cytoplasm is jelly-like material inside of the cell that fills all space between the nucleus
• Cytoplasm is made up of the cytosol- liquid part of the cytoplasm- and organelles- structures suspended in the cytoplasm that are used for carrying out particular functions.
• Nucleus: largest organelle in the cell

  • Structure: ovoid, spherical shape surrounded by porous double nuclear membrane and contains the nucleolus
  • Location: in cytoplasm
  • Function: stores DNA which are the blueprints of making proteins, controls the structure of the cell and the way it functions
• Ribosomes:

  • Structure: small, spherical
  • Location: free in the cytoplasm or attached to membranes and rough ER
  • Function: involved in protein production

  
• Golgi body/ Apparatus:

  • Structure: flattened, membranous bags stacked on top of each other
  • Location: cytoplasm, near nucleus
  • Function: modifies proteins and packages them into vesicles to be secreted from the cell

  
• Endoplasmic reticulum:

  • Structure: pairs of parallel membranes
  • Location: extends through the cytoplasm, connecting the cell membrane with the nuclear membrane
  • Function: provides a surface on which chemical reactions can occur, storage and transport of materials
  • Smooth ER: no ribosomes
  • Rough ER: ribosomes attached

  
• Mitochondria:

  • Structure: spherical, sausage shaped structure with a double membrane
  • Location: spread through the cytoplasm
  • Function: site of chemical reaction of cellular respiration

  
• Centrioles:

  • Structure: a pair of cylindrical structures
  • Location: usually near nucleus
  • Function: involved in the reproduction of the cell

  
• Lysosomes:

  • Structure: small spheres
  • Function: contain enzymes that break down proteins, lipids, nucleic acids and carbohydrates, also break down worn out organelles that are taken into the cell

  
• Cilia and flagella:

  Cilia- short and numerous, look like tiny hairs, line the windpipe, move mucous and trap particles

  Flagella- longer, usually only one or two, the only cell with flagella in the human body is found in sperm, allowing them to swim towards the egg
• Cytoskeleton is the framework of protein fibres that assist with cell movement and gives the cell its shape
• Microtubules are hollow rods that keep organelles in place or around the cell
• Microfilaments help to move materials around the cytoplasm and move the whole cell
• Inclusions:

  • haemoglobin
  • melanin
  • fat droplets
• Cell specialisation is each cell being designed to carry out a particular function in the body.
• Cell differentiation is the process by which a cell changes to become specialised for its function.