Structure
 Largest organelle
 Spherical
 Dark
patches=chromatin
Surrounded by nuclear
envelope
 Composed of 2 fluid
filled membranes
 Has nuclear poreallows large molecules
through
Nucleolus inside
Function
 Contains genetic material
 Chromatin consists of DNA and
proteins
 Contains instructions for
making proteins
 When cells divide, chromatin
condenses into visible
chromosomes
 Nucleolus makes RNA and
ribosomes.
Structure:
 Consists of flattened
membrane-bound sacs cisternae which are continuous
with the outer nuclear
membrane.
 RER- Ribosomes
Smooth ER- no Ribosomes
Function:
Smooth ER- Involved in synthesising, storing and
transporting lipids.
RER- Transports proteins made on attached
ribosomes (large surface area)
Golgi Apparatus
Structure:
 Stack of membrane-bound,
flattened sacs
Function:
 Receives proteins from the ER
 Modifies them e.g. adds sugar
(Post office) to make glycoproteins
 Packages proteins into vesicles to
be transported inside cell or to the
outside
 Produces secretory enzymes (like
those secreted by pancreas)
Mitochondria
Structure:
 2 membranes separated by a fluid
filled space
 Inner membrane is folded to form
cristae – provides large surface area
for the attachment of enzymes
involved in respiration.
 Central part is the matrix. Contains
protein, traces of DNA and lipids. DNA
allows mitochondria to produce its
own proteins. Enzymes found in the
matrix.
 Lots of mitochondria are found in
active cells (like muscle) which require
plentiful supply of ATP.
Function
 Site where ATP is
produced during
respiration
Chloroplasts
Structure:
 2 membranes
separated by fluid filled
space
 Inner membrane is
continuous with a
network of thylakoids
 A stack of thylakoids
is called a granum
 Chlorophyll
molecules are present
on these membranes.
Function:
 Site of photosynthesis
 Light energy is used to derive
carbohydrate molecules from
carbon dioxide.
Function:
 Contain digestive enzymes
which break down materials
(such as in white blood cells –
phagocytosis)
 Release enzymes to the
outside of the cell (exocytosis)
to destroy materials around the
outside of the cell
Structure:
 Spherical sacs surrounded
by a single membrane
 Break down old cells after
they have died (autolysis) and
digest worn out organelles
 Specialised lysosome
(acrosome) in head of sperm
cells helps it penetrate the egg
Organelles NOT surrounded by membranes
 Ribosomes
Centrioles
Ribosome
Structure
 No membrane
Very small organelles in the
cytoplasm and bound to rough
ER
 Consist of 2 subunits – large
sub-unit and small sub-unit
Function:
 Site of protein synthesis which acts
as an assembly line to use mRNA to
assemble proteins.
Centrioles
Structure
 No membrane
Small protein tubes of
microtubules.
Function:
 Form fibres in cell division known as
spindles which separate chromosomes.