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Found only in Plant cells
Cellulose cell wall- provides cell wit itscharacteristic shape.
Strong and elastic.Cells are held together by the sticky
middleamella.Large molecules enter the cell troughplasmodesmata-
cytosol filled channels.Plant cells contain large
vacuoles surrounded by the tonoplast membrane.Chloroplasts are
surrounded by a doublemembrane containing grana
–membranebound structures enclosing a fluid filled
cavity. This is where chlorophyll iscontained and the
light stage ofphotosynthesis takes place. The lamellae spread
the grana out for maimum lightabsorption. The Calvin cycle takes
place inhe surrounding stroma.
Found only in Animal cells
! pair of centrioles can be found close to
he nucleus in the centre of the "T#Cmicrotubule organising
centre%& they controlhe spindle.The MTOC also control the
cytoskeleton- aramework of protein fibres that control acells shape
and movement.Microvilli are supported by the cytoskeletonand
greatly increase the surface area of thecell.
Eukaryotic Cells
Contain a true nucleus i.e. The '(! iscontained in a double
nuclear membraneThey have numerous cell organelles madefrom
membranes
)ave an extracellular matrix surrounding the
plasmamembrane.'(! is surrounded by a nuclear envelope& the
outer layer ofwhich is part of the endoplasmic reticulum.(uclear
envelope is punctured with small pores that allowthe transport of
m*(!. !t each pore the outer and innermembranes are fused together
and the pore is encircled withtransport proteins.'(! is associated
with + histone proteins& which combine to
make nucleosomes.ucleolus is the area of the nucleus that stains
more darkly.,t is made up of chromosomes that always
associatetogether and are in control of ribosomal *(!
synthesis. ! polysome is the name given to many ribosomes
attachedonto an m*(! molecule.n/ymes embedded in the rough
endoplasmic reticulum modify the protein by adding short sugar
chains- creatingglyco proteinsSometimes tips of the * are 0budded1
off& and becometransport vesicles which migrate and merge
wit the plasma
membrane or organelles to Some vesicles
containingglycoproeinsmerge with the flattened sacs of the golgi
!ody.The smooth endoplasmic reticulum has a different
rolewithin the cell. Lipids such as fatty acids& phospholipids
andsteroids are synthesi/ed here."ysosomes separate en/ymes
from the cytoplasm by amem!rane envelope& creating optimum
conditions. Theyoften merge with vacuoles containing obsolete
organelles ormicroorganisms and digest themThe micro !ody is
also a membrane envelope surrounding
a number of en/ymes& which oidise fatty acids and
toicsubstances. !ll the membrane bound structures are part of
theendomem!rane system.The mitochondrion is the site of
aerobic respiration. ,t issurrounded by a double membrane&
enclosing the matri- thesite of the 2rebs cycle and the
cristae# where !TP issynthesised by the cytochrome
system.
Prokaryotic Cells'(! not enclosed within a nuclear envelope."ost
of the '(! is contained within a single circular molecule known as
a nucleoid.#ften there are small rings of '(! known as
plasmids& which allow genetic information to bepassed between
cells.,t has a cytosol- a cytoplasm with no
organelles.$i!osomes are still present& smaller than in
eukaryotes."ovement is achieved using a %lagellum & in an
anti clockwise rotation. Cells can reach up to 34 their own length
per second"any have pilli to stick to surfaces& sometimes
to swap plasmids.The plasma mem!rane is t only membrane structure
found in prokaryotes.
5acteria cells have a cell wall made from peptidoglycan&
providing a strong and rigid coating."any have a capsule& a
slimy layer of mucus type substance& which helps bacteria to
stick& andhelps to protect against en/yme and phagocyte
attack."ost bacteria cells are approimately the same si/e as
mitochondrion in eukaryotes '.( ) * um.
