cells
An animal cell
Plant cells
The cell Theory
• The cell theory states that all
living organisms are made of one
or more cells, cells are the basic
units of structure and function ,
and cells come only from pre
existing cells
Cells come in a shapes and sizes
• 1 meter = 100 cm
• 1cm= 10 mm
• 1mm= 1000 um
(Micrometer)
• 1um=1000 nm
(Nanometer)
there are two main types of cell
The are two main types of cell
• Prokaryotic cells do not
have a nucleus and
internal membranebound structures
• Most unicellular
organisms are
prokaryotes eg. Bacteria
Eukaryotic cells
• Eukaryotic Cells have a
nucleus and internal
membrane-bound
structures.
• Most multicellular
organisms are
eukaryotes.
• Eg. Yeast and algae
(unicellular, eukaryotes)
• Plant and animals
Common features of cells
• Cytoplasm – Gel like
material that protects,
supports and suspends
organelles.
• It contains dissolved
substances.
• It contains a
cytoskeleton of
microtubules and
filaments to give the cell
structure and allow
substances to move
about the cell.
Plasma membrane
• plasma membrane is the
outer layer of the cell.
• It protects the cell and
acts as a selective barrier,
letting some materials in
and keeping others out
• It is made of a lipid
bilayer (phospholipids)
and has proteins and
carbohydrates through it
The fluid mosaic model is used to
explain how membranes are flexible
• The phosphate
head is
hydrophilic
and the fatty
tail is
hydrophobic
so it forms a
bilayer with a
fatty insoluble
middle.
The nucleus and nucleolus
• Surrounded by the
nuclear membrane and
contains pores to let
substances in and out.
• It contains DNA in the
form of chromosomes
( eukaryotes)
• The nucleolus makes
ribosomes which travel
out to the cytoplasm
and are needed for
protein synthesis
The endoplasmic reticulum comes in
two types
• A series of folded
membranes
• Rough endoplasmic
reticulum (RER)
contains ribosomes.
This is where proteins are
made
• smooth endoplasmic
reticulum (SER) make
and store lipids ( Fats)
ribosomes
• Ribosomes are made up
of two subunits
• They can be free
floating in the
cytoplasm or attached
to the RER.
• Ribosomes make
proteins.
Vacuoles
• These are storage sacs
for the temporary storage
of materials such as food,
enzymes, waste.
• Plant cells have one large
vacuole surrounded by a
tonoplast membrane and
amyloplasts.
• animal cells have lots of
small vesicles
Mitochondria
• This is where cellular
respiration occurs
making ATP.
• the number of
mitochondria depends
on the type of cell.
Muscle cells have lots
Lysosomes
• Contain digestive
enzymes
• Digest excess or
worn organelles,
food particles,
viruses, and bacteria
• Surrounded by
membrane that
prevents it from
destroying the cell
• Can burst causing
cell death
Golgi apparatus
• These are tubular
membranes which ‘nip’
off at the ends to make
vesicles
• The golgi apparatus
sorts, modifies,
packages and transports
proteins so they can
move around the cell.
Centrioles (Animal Cells)
• They are micro-tubules
• These help with cell
reproduction by making
spindle fibres.
Chloroplasts ( plant cells)
• Chloroplast – Located in
plant cells, some
bacteria, and protists.
• Photosynthesis-Capture
light energy to produce
and store food
• Contain chlorophyllgreen pigment that
traps light
Flagella and cilia are made of
microtubules
• Whip like projections
• Hair like projections
that wave around
Cell wall ( plants only)
• Rigid outer covering made
of cellulose.
• Located outside the cell
membrane
• Provides support and
protection
• Helps produce turgor
pressure
• Contains holes called
plasmodesmata to allow
stuff in and out of cells
Intercellular junctions Animal cells
• Tight junctions join cells
together to make tissue.
• Desmosomes act like
rivets joining cells
together
• Gap junctions are
channels to allow
substances in and out