Structures

• Cell surface membrane:

  • plasma membrane
  • made of phospholipid bilayer

  Controls movement of substances into and out of the cell
• Nucleus:

  • has double membranes

  Contains genetic information for the synthesis of proteins
• Nuclear envelope:

  • attached to ER
  • 2 membranes
  • have nuclear pores

  Controls movement of substances between nucleus and cytoplasm
• Nucleolus:

  • densest region

  Site of ribosomal RNA (rRNA) synthesis, site of ribosome assembly
• Chromatin: DNA and its associated proteins
• Ribosomes:

  • smallest organelle
  • not bound by a membrane
  • made of rRNA, that is synthesised in nucleolus and some protein

  Site of protein synthesis
• Ribosome types:

  1. 80s ribosomes are larger, found in cytoplasm and RER of all eukaryotic
  2. 70s ribosomes are smaller, found in mitochondria and chloroplasts of eukaryotes, found in all prokaryotes
• Rough Endoplasmic Reticulum:

  • extensive, connected system of membranes
  • made of cisternae (flattened membrane sacs)
  • continuous with the nuclear envelope
  • 80s ribosomes


  Site of protein synthesis, and protein modification, transport protein to Golgi
• Smooth Endoplasmic Reticulum:

  • ER without ribosomes

  Site of lipid and steroid synthesis
• Golgi body:

  • made of cisternae
  • no connection between members
  • swellings at end of sacs for vesicle formation


  Modification of proteins and lipid, packaging molecules into vesicles for transport, formation of secretory vesicles for release of protein out of the cell, formation of lysosomes
• Lysosomes:

  • spherical, small sacs

  Breakdown or digest unwanted
• Mitrochondria:

  • has double membranes
  • has a small circular DNA
  • 70s ribosomes
  • divide by binary fission
  • have prokaryotic origin

  Site of aerobic respiration, produce energy in the form of ATP
• Chloroplasts:

  • two membranes
  • contain chlorophyll
  • thykaloid: flattened membrane sacs
  • grana: thykaloid stacks
  • stroma: interior solution
  • 70s ribosomes
  • small circular DNA
  • contain starch grains
  • divide by binary fission
  • prokaryotic origin

  Site of photosynthesis, light energy absorbed and water is used to synthesise ATP, ATP used to convert CO² into glucose
• Cell wall:

  • made of cellulose
  • permeable


  Provide structural support, prevent bursting, limit cell size
• Plasmodesma:

  • strands of cytoplasm passing through channels (no cell wall)


  Allow substabces to pass from cell to cell without passing through cell walls (e.g water, ATP)
• Vacuoles:

  • large, permanent, and central in plant cells
  • surrounded by a partially permeable membrane called tonoplast


  Store cell sap (contains water, ions, minerals, salts, pigments, sugars), stores waste products, vacuoles filled with water create a pressure called turgor pressure
• Centrioles & Centrosomes (pair):

  • hollow cylinder
  • made of 9 groups of 3 microtubules
  • not found in plant cells


  Involved in cell division
• Microtubules:

  • made from tubulin


  Provide mechanical support to the cell, help move vesicles, organelles, and cell components within the cell, hold membrane-bound organelles in place, form spindle fibres during nuclear division
• Microvilli:

  • finger-like projections of the cell surface membrane


  Increase surface area of the cell membrane for absorption, secretion of enzymes, digestion at the cell surface, excretion of waste substances