NZ

Eukaryotic Organelles

Nucleus

Structure

  • contains the cell’s DNA
  • double membrane called the nuclear envelope surrounds it
  • nuclear pores are gaps in the nuclear envelope
  • contains the nucleolus

Function

  • controls the cell’s activities
  • pores allow entry/exit of materials such as ribosomes and RNA
  • nucleolus assembles ribosomes

Mitochondria

Structure

  • enclosed in a double membrane
  • the inner membrane has folded extensions called cristae
  • the interior is called the matrix, and contains enzymes involved in cellular respiration

Function

  • cristae provide a large surface area for attaching enzymes
  • involved in cellular respiration and producing ATP

Chloroplast

Structure

  • enclosed by the chloroplast envelope
  • contains thylakoids which contain the pigment chlorophyll
  • thylakoids are arranged in stacks called grana
  • fluid-filled interior is called the stroma

Function

  • the first stage of photosynthesis - light absorption - takes place in the thylakoids
  • the second stage of photosynthesis - synthesising sugars - takes place in the stroma

Endoplasmic Reticulum (ER)

Structure

  • 3d system of sheet-like membranes

  • continuous with the nuclear envelope

  • there are two types - rough and smooth

  • rER (rough) has ribosomes attached on the outer surface, while sER (smooth) does not.

Function

  • rER has a role in protein synthesis
  • sER synthesises, stores and transports lipids and carbohydrates

Golgi Apparatus

Structure

  • consists of a stack of membranes called cisternae (singular: cisterna)
  • Golgi vesicles form around the outside
  • the interior is called the lumen

Function

  • it modifies the proteins that pass through it - this includes adding more protein parts or adding lipid/carbohydrate parts too
  • it “labels“ the proteins to allow them to be sorted and sent to their desired location
  • transportation is done via golgi vesicles

Lysosome

Structure

  • specialist forms of vesicles which contain hydrolitic enzymes

Function

  • they remove useless and potentially dangerous material and reuse the useful parts
  • the hydrolitic enzymes are enclosed in a membrane so that they don’t accidentally destroy needed organelles
  • they can release the hydrolitic enzymes outside of the cell to destroy material there

Ribosomes

Structure

  • small granules formed in the nucleolus
  • 80S in eukaryotic cells, slightly smaller 70S in prokaryotic cells
  • contain a large sub-unit and a small sub-unit

Function

  • the site of protein synthesis

Cell Wall

Structure

  • cormed outside of the cell membrane
  • in plants, it is made out of the polysaccharide cellulose

Function

  • they provide mechanical strength to prevent the cell from bursting

Vacuole

Structure

  • a fluid filled sac bound by a single membrane called the tonoplast
  • there is usually one large central vacuole in plant cells
  • the vacuole contains a solution of mineral salts and sugars

Function

  • they can make plant cells turgid/flaccid
  • they can also contain certain pigments in petals which can attract the attention of pollinating insects