Cell Organelles

• Vesicle


  A membrane bound sac that transports materials into, out of or within the cell
• Cytoplasm


  Thick fluid within the cell membrane and all the structures suspended in it
• Cytosol


  The liquid part of the cytoplasm: 75-90% water
• Organelles


  Specialised structures suspended in the cytoplasm
• Centrioles


  A pair of cylindrical structures usually located near the nucleus involved in the reproduction of the cell
• Endoplasmic reticulum (ER)


  Pairs of parallel membranes extending through the cytoplasm and connecting the cell membrane with the nucleus membrane
• Endoplasmic reticulum (ER)


  • Most have ribosomes attached - rough or granular ER
  • Some have no ribosomes - smooth or agranular
• Ribosomes


  • Very small and spherical, may be free in the cytoplasm but most are attached to membranes
  • Amino acids are joined together at the ribosomes to make proteins
• Cytoskeleton


  Consists of microfilaments and microtubules that give the cell its shape and assist the movement of materials, organelles or the whole cell
• Inclusions


  Substances that are not part of the cell structure but are found in the cytoplasm, e.g. haemoglobin found in the red blood cells
• Lysosomes


  • Small spheres that contain enzymes able to break down proteins, lipids, nucleic acids and some carbohydrates
  • Lysosomes break down materials that are taken into the cell or break down worn out organelles
• Nucleolus


  Composed mainly of RNA, DNA and nucleolus are suspended in a jelly-like nucleoplasm
• Nucleus


  • Usually ovoid or spherical, contains the genetic material mostly DNA
  • Separated from the cytoplasm by a nuclear membrane
  • The membrane is double and has gaps (nuclear pores) through which large molecules can pass
• Mitochondria


  • Spherical or elongated structures spread through the cytoplasm
  • Have a double membrane - the outer is smooth, the inner one folded in towards the centre of the mitochondrion
  • Mitochondria release energy for the cell through the process of respiration
• Golgi Body


  • Flattened membranous bags stacked on top of each other
  • They modify proteins and package them in vesicles for secretion from the cell
  • Vesicles are pinched off from the edges of the membrane
• Cell membrane


  • The outer boundary of the cell that separated it from the neighbouring cells and from the external environment
  • Made up of a double layer of lipid molecules and associated proteins
  • The cell membrane determines which substances get into or out of a cell
  • It separates the cell from the environment outside the cell and from neighbouring cells
  • It is very thin, too thin to be seen with a light microscope