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