structure and function of organelles

• Nucleus structure

  • envelope - double membrane
  • pores
  • nucleoplasm - granular, jelly like material
  • chromosomes - protein bound, linear DNA
  • nucleolus -smaller sphere inside , site of rRNA production and makes ribosomes
• Nucleus function


  • site of DNA replication and transcription (making mRNA)
  • contains DNA for each cell
  • site of ribosome synthesis
• Flagella


  structure: whip like structure

  function: for mobility, sensory organelle for chemical stimuli
• cillia structure

  hairlike projections out of cells
• cillia function

  • mobile cillia help move substances in a sweeping motion. in the trachea to sweep mucus up and out of trachea to prevent lung infection
  • stationary cillia important in sensory organs like the nose.
• centrioles

  structure: made of microtubules. occur in pairs to make a centrosome

  function: Involved in producing spindle fibres and organisation of chromosomes in cell division
• Cytoskeleton structure

  • network of fibres found in cytoplasm all over cell
  • has microfilaments, microtubules and intermediate fibres
• cytoskeleton function

  • microfilaments are responsible for cell movement
  • provide mechanical strength to cells, helps maintain stability and shape of cell. many organelles bound to cytoskeleton
  • microtubules create scaffold like structure
  • intermediate fibres provide mechanical strength
• RER + SER structure

  both have cisternae (folded membranes); rough ER has ribosomes on cisternae
• RER + SER function

  • RER - protein synthesis for proteins destined to leave cell. proteins transport thru RER and into secretory vesicles
  • SER - synthesis and store lipids and carbohydrates
• GA + vesicle structure

  • folded membranes making cisternae
  • secretory vesicles pinch off of cisternae
• GA + vesicle function

  • add carbs to proteins to make glycoproteins
  • make secretory enzymes
  • secrete carbs
  • transport, modify + store lipids
  • make lysosomes
  • finished products -> cell surface membrane in secretory vesicles ->fuse with membrane -> contents released
• Lysosome structure

  bags of digestive enzymes
• lysosome function

  • hydrolyse phagocytic cells
  • completely break down dead cells
  • exocytosis - release enzymes out of cell to destroy material
  • digests worn out organelles for reuse of materials
• Mitochondria structure

  • double membrane
  • fluid centre mitochondrial matrix
  • loop of mitochondria DNA
  • cristae (folded inner membrane)
• mitochondria function

  • site of aerobic respiration
  • site of ATP production
  • DNA to code for enzymes needed in respiration
• 80s Ribosomes

  structure: small and large, 2 sub units of protein and rRNA

  function: protein synthesis
• plasma membrane structure

  • phospholipid bilayer - molecules embedded and attatched on outside (proteins, carbs, cholesterol)
• plasma membrane function

  controls the entrance and exit of molecules
• production + secretion of proteins

  1. polypeptide chains synthesised on RER (ribosomes on outside)
  2. these chains move to cisternae in RER + packaged into vesicles + sent to GA by Cytoskeleton
  3. in GA, proteins modified and packaged into vesicles
  4. secretory vesicles carry proteins to cell surface membrane, fuses + releases proteins by exocytosis