© SSER Ltd.
Eukaryotic cells are organised around systems of membranes
Cells are surrounded
by a plasma membrane
Plasma Membrane
Cytoplasm
The plasma
membrane serves
as a boundary
between the cell
and its
environment
Suspended in the
Cell are numerous
specialised
membrane-bound
structures called
organelles
It retains the cell
as a unit and, due
to its selective
permeability,
regulates the
movement of
materials into and
out of the cell
Plasma membranes vary in thickness between
7.5 and 10 nm (nanometres - 10-9 m)
Animal cells, with
the exception of
mammalian red blood
cells, possess a nucleus
The nucleus contains the hereditary material
The nucleus is a
large spherical or
oval organelle
surrounded by a
double membrane
called the
nuclear envelope
During cell
division hereditary
material
condenses into
chromosomes
The nuclear envelope
is perforated by
nuclear pores
Nuclear Envelope
Nuclear Pore
Nucleoplasm
The fluid contained
within the nucleus
is called
nucleoplasm
The Nucleolus is
a small densely
staining disc within
the nucleus
The nucleus contains the hereditary material and
controls the activities of the cell
The nuclear envelope is a double-layered structure consisting
of two adjacent membranes, 40-70 nm apart.
The envelope is perforated by pores.
The pores enable communication
to occur between the nucleus
and the cytoplasm
ribosomes
two membranes (envelope)
Ribosomes are often found attached
to the external membrane
mitochondrion
nuclear envelope
nucleolus
chromatin
Mitochondria are rod-shaped
organelles concerned with
energy production
Much of the process
of aerobic respiration
occurs within the
mitochondria
Mitochondria are loosely termed the
‘powerhouses of the cell’
Each mitochondrion
consists of an outer
smooth membrane
and an inner
folded membrane
The folds are
called cristae
Outer smooth
membrane
Inner folded membrane
Fluid matrix
endoplasmic
reticulum
fluid matrix
cristae
outer
membrane
Extending from the nuclear membrane and
continuous with it is the rough endoplasmic reticulum
Free ribosomes are
also found within
the cell
Reticulum means
network and the
rough endoplasmic
reticulum is an
extensive network of
flattened sacs that
extend throughout
the cell
Rough endoplasmic reticulum is studded with
ribosomes which are the sites of protein synthesis
Rough endoplasmic
reticulum provides
a transport system
for newly
synthesised proteins
Proteins are synthesised at the
ribosomes and move into
the cavities of the endoplasmic
reticulum
Newly synthesised proteins
are transported to
different parts of the cell
Cavity of
endoplasmic reticulum
Ribosomes
- sites of
PROTEIN SYNTHESIS
cavity of
endoplasmic reticulum
ribosome
A second type of endoplasmic reticulum
also occurs
This is the smooth endoplasmic
reticulum
Unlike the rough
endoplasmic
reticulum, there are
no ribosomes
associated with the
smooth endoplasmic
reticulum
SMOOTH ENDOPLASMIC RETICULUM
Smooth
endoplasmic
reticulum consists
of a system of
branching tubes
and is concerned
with the synthesis
of steroids
and fatty acids
The Golgi Apparatus or
Golgi Body is a stack of 4 to 8
membrane-bound sacs
located close to the nucleus
Proteins and lipids
are modified and
packaged within the
Golgi Apparatus
in preparation for
distribution within
the cell or export
from the cell
Materials are concentrated and packaged into
vesicles
Secretory cells
possess well
developed
Golgi Bodies
The principal role of the Golgi Apparatus is that
of secretion from the cell
The Golgi Apparatus exists as stacks of closely packed
membrane bounded sacs or cisternae
vesicles
cisternae
Clusters of ‘pinched off’
portions of the Golgi body
form a vesicles
around the array of cisternae
The Golgi Apparatus is highly
developed in cells secreting proteins
or complex carbohydrates
stacked
membranes
Golgi
vesicles
Lysosomes perform a
number of functions
Destruction of
bacteria and
other debris
taken into
the cell
Destruction of
ageing, redundant
cell organelles
Lysosomes are membrane bound
organelles that contain digestive enzymes
Destruction of
the entire cell
when damaged
or diseased
Release of the
digestive enzymes
FROM the cell to
degrade other cells
Smooth endoplasmic
reticulum
Plasma membrane
Golgi body
Lysosome
Mitochondrion
Free ribosomes
Rough endoplasmic
reticulum
Nucleus
Smooth endoplasmic
reticulum
Plasma membrane
Golgi body
Lysosome
Mitochondrion
Free ribosomes
Rough endoplasmic
reticulum
Nucleus
Smooth endoplasmic
reticulum
Plasma membrane
Golgi body
Lysosome
Mitochondrion
Free ribosomes
Rough endoplasmic
reticulum
Nucleus