Cell Ultrastructure

• Golgi body/ Golgi apparatus


  • Process, package and distribute proteins made within the cell
  • Stack of sac-like membranes
  • Involved in secretion

  
• Lysosomes


  • A spherical sac bounded by a single membrane
  • Help white blood cells destroy bacteria in the process of phagocytosis
  • Destroy the worn-out organelles inside cells
  • Contain digestive enzymes

  
• Centrioles

  Two short bundles of nine microtubules

  • Located just outside the nucleus in a clear area of cytoplasm called the centrosome

  
• Cilia and undulipodia

  • Hair-like extensions from cells which allow movement by sliding past each other
  • Cilia – short, many found on one cell. Found in the trachea and bronchi
  • Undulipodia – long, only one or two found on each cell

  
• Cell wall

  Only in plant cells

  • Made of cellulose
  • Allows water + dissolved molecules to pass through
  • Plasmodesmata connect the cytoplasm of adjacent cells for more rapid exchange of molecules

  
• Chloroplasts

  • Grana - a stack of thylakoid discs that contain chlorophyll molecules
  • Stroma – fluid containing photosynthetic enzymes
  • Has a double membrane

  
• Vesicles and vacuoles

  • Store food, water, or waste materials
  • Vesicles: small membrane-bound sacs used for transport within cells
  • Plant cells have large permanent vacuoles. The surrounding membrane is called a tonoplast - maintains turgor for support

  
• Mitochondria 


  -Site of respiration

  • ATP made here
  • Long and thin + Double membrane
  • Matrix (liquid part) and cristae (folds of the inner membrane)
  • Cristae increase the surface area for attachment of respiratory enzymes

  
• Ribosomes

  • Made of two protein sub-units – smallest organelle (22 nm)
  • Site of protein synthesis in cells

  
• Endoplasmic reticulum (ER)


  • folded membranes that form interconnected sacs/tubes called cisternae
  • Rough ER has ribosomes attached – involved in protein synthesis and transport
  • Smooth ER - site of lipid synthesis

  
• Plasma membrane (cell surface membrane)

  • Controls what enters and leaves the cell
  • Place of communication with environment and other cells

  
• Nucleus

  -Contains all of the cell's DNA

  • Nucleolus - darker region where ribosomes and RNA are made
  • Nuclear envelope – double membrane surrounding nucleus that has nuclear pores (holes) for material exchange between the nucleus and cytoplasm

  
• Cytoplasm

  • Cytoplasm: Jelly-like substance holding all the cell's organelles
  • Cytosol: Water with dissolved substances in it
  • network of protein filaments used for transport within the cell + providing support and strength