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8/8/2019 Cell Structure [Report in Botany IV]
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8/8/2019 Cell Structure [Report in Botany IV]
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If you are Pnoy, what name couldIf you are Pnoy, what name could
you give to the three pictures?you give to the three pictures?
Answers:Prokaryotic cell (bacteria)
Eukaryotic cell (animal cell)Eukaryotic cell (plant cell)
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Eukaryotic Cell OrganellesEukaryotic Cell Organelles
1. Nucleus: Control center of the cell
(command). Spherical in shape which
contains the DN A, the geneticmaterials.
-The nucleus is the most obvious
organelle in any eukaryotic cell. It isenclosed in a double membrane and
communicates with the surrounding
cytosol via numerous nuclear pores.
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Within the nucleus is the DN AWithin the nucleus is the DN A
responsible for providing the cell withresponsible for providing the cell with
its unique characteristics. The DN A isits unique characteristics. The DN A is
similar in every cell of the body, butsimilar in every cell of the body, butdepending on the specific cell type. depending on the specific cell type.
When a cell is dividing, theWhen a cell is dividing, the nuclear nuclear
chromatin (DN A and surroundingchromatin (DN A and surroundingprotein)protein) condenses into chromosomescondenses into chromosomes
that are easily seen by microscopy.that are easily seen by microscopy.
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a.a. Nucleolus:Nucleolus:
The prominent structureThe prominent structure
inside the nucleus. Theinside the nucleus. The
nucleolus produces ribosomesnucleolus produces ribosomes
(rRN A)(rRN A), which move out of the, which move out of thenucleus and take positions onnucleus and take positions on
the rough endoplasmic reticulumthe rough endoplasmic reticulum
where they are critical in proteinwhere they are critical in protein
synthesis.synthesis.
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b. Nuclear poreb. Nuclear pore ± ± tiny pores or tiny pores or openings in the nuclear membraneopenings in the nuclear membrane
which allows the nucleus towhich allows the nucleus to
communicate with the membranouscommunicate with the membranousnetwork in the cytoplasm & E.R.network in the cytoplasm & E.R.
c. Nuclear envelopec. Nuclear envelope-- a doublea doublemembrane that surrounds the nucleus.membrane that surrounds the nucleus.
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2. Cytoplasm: This is a collective term for 2. Cytoplasm: This is a collective term for
thethe cytosolcytosol plus the organelles suspendedplus the organelles suspendedwithin the cytosol. The cytosol is the "soup"within the cytosol. The cytosol is the "soup"
within which all the other cell organelleswithin which all the other cell organelles
reside and where most of the cellular reside and where most of the cellular metabolism occurs. metabolism occurs.
Although gel Although gel--like or watery material, thelike or watery material, the
cytosol is full of proteins that control cellcytosol is full of proteins that control cellmetabolism.metabolism.
It is found between the cell membraneIt is found between the cell membrane
and nucleus.and nucleus.
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Two Regions of ProtoplasmTwo Regions of Protoplasm
1. Cytoplasm ± protoplasm outside
the nucleus.
2. Karyoplasm or Nucleoplasm ±
protoplasm inside the nucleus.
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3. Cell Membrane: also known as3. Cell Membrane: also known as
plasma membrane or plasmalemma. plasma membrane or plasmalemma. -- It gives shape to the cell andIt gives shape to the cell and
controls what enters and leaves out thecontrols what enters and leaves out the
cell (semicell (semi--permeable membrane).permeable membrane).
--Sometimes, it serves as an organSometimes, it serves as an organ
for locomotion.for locomotion.
-- Every cell is enclosed in aEvery cell is enclosed in a
membrane, a double layer of glycolipidmembrane, a double layer of glycolipid
or phospholipids (fat or lipid bilayer).or phospholipids (fat or lipid bilayer).
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The exposed heads of the bilayer The exposed heads of the bilayer
areare "hydrophilic" (water loving),"hydrophilic" (water loving),meaning that they are compatible withmeaning that they are compatible with
water both within the cytosol andwater both within the cytosol and
outside of the cell. outside of the cell. However, the hidden tails of theHowever, the hidden tails of the
phosopholipids arephosopholipids are "hydrophobic""hydrophobic"
(water fearing),(water fearing), so the cell membraneso the cell membrane
acts as a protective barrier to theacts as a protective barrier to the
uncontrolled flow of water . uncontrolled flow of water .
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4. Ribosomes: Protein factories of the cell (site of 4. Ribosomes: Protein factories of the cell (site of
proteinsynthesis).proteinsynthesis).
-- tiny dottiny dot--like or bead like structures madelike or bead like structures made
up of tRN A. They may be free or attached to theup of tRN A. They may be free or attached to the
E.R. in the cytoplasm.E.R. in the cytoplasm.-- Each ribosome comprises two parts, aEach ribosome comprises two parts, a
large subunit and a small subunit. Messenger large subunit and a small subunit. Messenger
RN A from the cell nucleus is movedRN A from the cell nucleus is moved
systematically along the ribosome where transfer systematically along the ribosome where transfer
RN A adds individual amino acid molecules to theRN A adds individual amino acid molecules to the
lengthening protein chain.lengthening protein chain.
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5. Endoplasmic Reticulum: Manufacturers,5. Endoplasmic Reticulum: Manufacturers,
Shipper or Channels of the cell.
Shipper or Channels of the cell.
The ER is a continuation of the outer The ER is a continuation of the outer
nuclear membrane.nuclear membrane.It is a set of folded membranes foundIt is a set of folded membranes found
throughout the cell.throughout the cell.
It is just like tiny canals through the cellIt is just like tiny canals through the cellformed by two parallel membranes.formed by two parallel membranes.
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Two Types of E.R.Two Types of E.R.
1. a. Smooth endoplasmic reticulum is so
named because it appears smooth by
electron microscopy. Smooth ER playsdifferent functions depending on the
specific cell type including lipid and
steroid hormone synthesis, breakdownof lipid-soluble toxins in liver cells, and
control of calcium release in muscle
cell contraction.
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b. Rough Endoplasmic Reticulum:b. Rough Endoplasmic Reticulum:
-- It appears "pebbled" by electronIt appears "pebbled" by electron
microscopy due to the presence of microscopy due to the presence of
numerous ribosomes on itsnumerous ribosomes on itssurface. surface.
-- Proteins synthesizedProteins synthesized onon thesethese
ribosomes collect in theribosomes collect in theendoplasmic reticulum for transportendoplasmic reticulum for transport
throughout the cell.throughout the cell.
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6. Golgi apparatus6. Golgi apparatus ± ± by Camillo Golgi. by Camillo Golgi.
-- It is the Packaging center of theIt is the Packaging center of the
cell.cell.
-- is a membraneis a membrane--bound structurebound structurewith a single membrane. with a single membrane.
-- It is actually a flattened stack of It is actually a flattened stack of
membranemembrane--bound vesicles that arebound vesicles that areimportant in packaging macromoleculesimportant in packaging macromolecules
for transport elsewhere in the cell. for transport elsewhere in the cell.
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-- The stack of larger vesicles isThe stack of larger vesicles is
surrounded by numerous smaller surrounded by numerous smaller
vesicles containing those packagedvesicles containing those packaged
macromolecules.macromolecules.-- The enzymatic or hormonalThe enzymatic or hormonal
contents of lysosomes, peroxisomescontents of lysosomes, peroxisomes
and secretory vesicles are packaged inand secretory vesicles are packaged inmembranemembrane--bound vesicles at thebound vesicles at the
periphery of the Golgi apparatus.periphery of the Golgi apparatus.
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7. Lysosome: Suicide bags of the7. Lysosome: Suicide bags of the
cell. cell. ´Lyso´Lyso´́--dissolving power anddissolving power and³³somesome´́ ± ± body.body.
-- Lysosomes contain hydrolyticLysosomes contain hydrolytic
enzymes necessary for enzymes necessary for intracellular intracellular digestion.digestion. They are spherical sacsThey are spherical sacs
or vesicles which are common inor vesicles which are common in
animal cells, but rare in plant cells. animal cells, but rare in plant cells.
Hydrolytic enzymes of plant cells areHydrolytic enzymes of plant cells are
more often found in the vacuole.
more often found in the vacuole.
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The powerful digestive
(hydrolytic) enzymes are capableof breaking down and destroying
a number of important cellular constituents.
Once the membrane is
damaged, the lysosome releasesits content into the cytoplasm
and may destroy the entire cell.
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8. Peroxisome: are membrane8. Peroxisome: are membrane--boundbound
packets or vesicles of packets or vesicles of oxidativeoxidativeenzymes. enzymes.
In plant cells, peroxisomes play aIn plant cells, peroxisomes play a
variety of roles including convertingvariety of roles including convertingfatty acids to sugar and assistingfatty acids to sugar and assisting
chloroplasts in photorespiration. chloroplasts in photorespiration.
In animal cells, peroxisomesIn animal cells, peroxisomes
protect the cell from its own productionprotect the cell from its own production
of toxic hydrogen peroxide. of toxic hydrogen peroxide
.
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As an example, white blood As an example, white blood
cells produce hydrogen peroxide tocells produce hydrogen peroxide tokill bacteria.kill bacteria.
TheThe oxidative enzymesoxidative enzymes inin
peroxisomes break down theperoxisomes break down the
hydrogen peroxide into water andhydrogen peroxide into water and
oxygen.oxygen.It functions to metabolize fats or It functions to metabolize fats or
lipids such as liver cells.lipids such as liver cells.
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9.Secretory Vesicle: Cell secretions
9.Secretory Vesicle: Cell secretionse.g. hormones, neurotransmitterse.g. hormones, neurotransmitters --
are packaged in secretory vesiclesare packaged in secretory vesicles
at the Golgi apparatus.at the Golgi apparatus.
-- The secretory vesicles are
The secretory vesicles arethen transported to the cell surfacethen transported to the cell surface
for release.for release.
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10. Mitochondria: the Power centers of 10. Mitochondria: the Power centers of
the cell. the cell. RodRod--shaped and usually foundshaped and usually found
in the muscle cells.in the muscle cells.
--It provides energy that the cellIt provides energy that the cellneeds in order to move, divide, produceneeds in order to move, divide, produce
secretory products and contracts.secretory products and contracts.
-- They are about the size of They are about the size of bacteria but may have different shapesbacteria but may have different shapes
depending on the cell type. depending on the cell type.
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Mitochondria are membraneMitochondria are membrane--
bound organelles, and like thebound organelles, and like the
nucleus have anucleus have a double membranedouble membrane.
. The outer membrane is fairlyThe outer membrane is fairly
smooth. But the inner membrane issmooth. But the inner membrane is
highly convoluted, forming foldshighly convoluted, forming folds(cristae). (cristae).
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The cristae greatly increase theThe cristae greatly increase the
inner membrane's surface area. inner membrane's surface area.
It is on these cristae that foodIt is on these cristae that food
(sugar) is combined with oxygen to(sugar) is combined with oxygen toproduceproduce ATP ATP -- the primary energythe primary energy
source for the cell.source for the cell.
Mitochondria is the site of Mitochondria is the site of
cellular respiration.cellular respiration.
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11.Vacuole: Storage tanks of the
11.Vacuole: Storage tanks of thecell / water bag.cell / water bag.
-- A vacuole is a membrane A vacuole is a membrane--
bound sac that plays roles inbound sac that plays roles inintracellular digestionintracellular digestion and theand the
release of cellular waste products. release of cellular waste products
. -- In animal cells,In animal cells, vacuolesvacuoles areare
generallygenerally smallsmall called vesicles. called vesicles.
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-- The plant cell vacuole alsoThe plant cell vacuole also
regulatesregulates turgor pressureturgor pressure in the cell. in the cell.
Water collects in cell vacuoles,Water collects in cell vacuoles,
pressing outward against the cell wallpressing outward against the cell walland producing rigidity in the plant. and producing rigidity in the plant.
-- TheThe turgor pressureturgor pressure is responsibleis responsible
for thefor the crispnesscrispness of fresh vegetables.of fresh vegetables.-- Without sufficient water, turgor Without sufficient water, turgor
pressure drops and the plant wilts. pressure drops and the plant wilts.
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12. Cell Wall (plant cells only): Plant12. Cell Wall (plant cells only): Plantcells have a rigid, protective cellcells have a rigid, protective cell
wall made up of polysaccharideswall made up of polysaccharides(cellulose).(cellulose).
-- The cell wall provides andThe cell wall provides and
maintains the shape of these cellsmaintains the shape of these cellsand serves as a protective barrier . and serves as a protective barrier .
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13. Chloroplast (plant cells only): It is13. Chloroplast (plant cells only): It is
made up of a double outer membrane. made up of a double outer membrane. Within theWithin the stromastroma are other membraneare other membrane
structuresstructures -- thethe thylakoidsthylakoids. Thylakoids. Thylakoids
appear in stacks called "appear in stacks called "granagrana""(singular = granum). (singular = granum).
These organelles contain the plantThese organelles contain the plant
cell's chlorophyll responsible for thecell's chlorophyll responsible for the
plant's green color . plant's green color
.
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Pant Pigments:Pant Pigments:
a.Chlorophylla
.Chlorophyll (green)(green)
--the primary pigmentthe primary pigmentin plants.in plants.
b. b. CarotenoidsCarotenoids (red, orange, or yellow)(red, orange, or yellow) ± ± ItIt
is the accessory pigments in plants. is the accessory pigments in plants
. 1. 1. carotenecarotene (an orange pigment found(an orange pigment found
inin carrotscarrots))
2.
2. luteinlutein (a yellow pigment found in(a yellow pigment found infruits and vegetables)fruits and vegetables)
3. 3. lycopenelycopene (the red pigment(the red pigment
responsible for the color of responsible for the color of tomatoestomatoes).
).
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c. Anthocyaninsc. Anthocyanins (red & violet)(red & violet) --ItIt
provides color in leaves, plant stem,provides color in leaves, plant stem,
roots, flowers, and fruits.roots, flowers, and fruits.
Most visible in petals of flowers. Most visible in petals of flowers
. d.Leucoplastsd.Leucoplasts // amyloplastsamyloplasts ± ± aa
colorless plastid that is present in rice,colorless plastid that is present in rice,
corn & potatoes or corn & potatoes or starchystarchy crops.crops.-- they contain oil, starch grains &they contain oil, starch grains &
proteins.proteins.
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Green plantsGreen plants have six closelyhave six closely--relatedrelated
photosynthetic pigments (in order of photosynthetic pigments (in order of increasing polarity):increasing polarity):
1. 1. CaroteneCarotene -- an orange pigmentan orange pigment
2. 2. XanthophyllXanthophyll -- a yellow pigmenta yellow pigment3. 3. PhaeophytinPhaeophytin aa -- a graya gray--brown pigmentbrown pigment
4. 4. PhaeophytinPhaeophytin bb -- a yellowa yellow--brown pigmentbrown pigment
5. 5. ChlorophyllChlorophyll aa -- a bluea blue--green pigmentgreen pigment6. 6. ChlorophyllChlorophyll bb -- a yellowa yellow--green pigmentgreen pigment
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Chlorophyll aChlorophyll a is the mostis the most
common of the six, present in everycommon of the six, present in everyplant that performs photosynthesis. plant that performs photosynthesis.
ChlorophyllChlorophyllbb
is a form of is a form of chlorophyllchlorophyll. Chlorophyll b helps in. Chlorophyll b helps in
photosynthesis by absorbing lightphotosynthesis by absorbing light
energy and it is more soluble thanenergy and it is more soluble thanchlorophyll a because of itschlorophyll a because of its
carbonyl group.
carbonyl group.
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14. Centrosome or MICROTUBULE14. Centrosome or MICROTUBULE
ORGANIZING CENTER (MTOC), isORGANIZING CENTER (MTOC), isan area in the cell wherean area in the cell where
microtubulesmicrotubules are produced. are produced
. It is found just outside theIt is found just outside the
nucleus.nucleus.
It consists of two rodIt consists of two rod--shapedshapedcentriolescentrioles which are right angles towhich are right angles to
each other .
each other .
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15.Centriole (animal cells only): a
15.Centriole (animal cells only): arodrod--shaped structure that aids inshaped structure that aids in
cell divisioncell division process and formationprocess and formation
of spindle fibers. of spindle fibers. Each centriole is a ring of nineEach centriole is a ring of nine
groups of fused microtubules. groups of fused microtubules
. Microtubules (and centrioles)Microtubules (and centrioles)
are part of the cytoskeleton.are part of the cytoskeleton.
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16.Cytoskeleton:
16.Cytoskeleton:-- It helps to maintain cellIt helps to maintain cell
shape. Its primary importance is inshape. Its primary importance is in
cell motilitycell motility (The internal movement(The internal movementof cell organelles, as well as cellof cell organelles, as well as cell
locomotion and muscle fiber locomotion and muscle fiber contraction could not take placecontraction could not take place
without the cytoskeleton).without the cytoskeleton).
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-- The cytoskeleton is anThe cytoskeleton is an
organized network of three primaryorganized network of three primaryprotein filaments:protein filaments:
1.microtubules
1.microtubules2. actin filaments (microfilaments)2. actin filaments (microfilaments)
3. intermediate fibers3. intermediate fibers
( These three provide the cells with( These three provide the cells withstructural support, shape andstructural support, shape and
motility)motility)
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Did You Know???Did You Know???
Pili / pilus ± it joins bacterial cells in
preparation for the transfer of DN A from
one cell to another .Plasmodesmata ± channels that connect
plant cells together through their walls.
Desmosomes ± the intercellular junctionbetween animal cells.
Matrix - a semi-fluid substance at the
center of mitochondria.
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MesosomesMesosomes -- an organelle of bacteria thatan organelle of bacteria that
appears as an invagination of theappears as an invagination of the
plasma membrane and functions either plasma membrane and functions either
in DN A replication and cell division or in DN A replication and cell division or
excretion of exoenzymes.excretion of exoenzymes.
HistonesHistones -- are the proteins closelyare the proteins closely
associated with DN A molecules. associated with DN A molecules.
-- They are responsible for the
They are responsible for thestructure of structure of chromatinchromatin and playand play
important roles in the regulation of important roles in the regulation of
gene expression. gene expression.
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Comparison Between ProkaryoticComparison Between Prokaryotic
and Eukaryotic Cellsand Eukaryotic Cells
Characteristic Prokaryotes Eukaryotes
Size of cell Typically 0.2-2.0mm in diameter Typically 10-100mm in diameter
Nucleus No nuclear
membrane or
nucleoli(nucleoid)
True nucleus,
consisting of
nuclear membrane &
nucleoli
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Characteristic Prokaryotes Eukaryotes
Membrane-enclosed
organelles .
Absent Present;examples
include
lysosomes,
Golgi complex,endoplasmic
reticulum,
mitochondria &
chloroplasts
Flagella Consist of two
protein building
blocks
Complex;
consist of
multiple
microtubules
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Glycocalyx Present as a
capsule or slime
layer
Present in some
cells that lack a
cell wall
Cell wall Usually present;
chemically
complex (typicalbacterial cell wall
includes
peptidoglycan)
peptidoglyc an, asi ngle l ar ge
polymer of ami no
acid s and sug ar
When present,
chemically
simple , cell wallnot made of
peptidoglycan
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Plasma
membrane
None or no
carbohydrates and
generally lacks
sterols
Sterols and
carbohydrates
that serve as
receptors
present
Cytoplasm No cytosketeton or cytoplasmic
streaming
Cytoskeleton;cytoplasmic
streaming
Ribosomes Smaller size (70S) Larger size(80S); smaller
size (70S) in
organelles
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Chromosome
(DNA)
arrangement
Single circular
chromosome;
lacks histones
Multiple linear
chromosomes
with histones
Cell division Binary fission Mitosis
RNA & DNA,
Proteins
Central body or
nucleoid;cytoplasm
Nucleus;
cytoplasm
Sexual
reproduction
No meiosis;
transfer of DNAfragments only
(conjugation)
Involves meiosis
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Chloroplast or
Plastids
No true plastids True plastids
present in
photosyntheticform
Cellular
Organization
Unicellular or
Colonial
Multicellular,
unicellular andcolonial
Examples Bacteria -
Escherichia Coli
(E. Coli),lactobacillus, and
samonella;
cyanobacteria(blue
-green bacteria)
Paramecium,
amoeba, euglena,
chlorella, andsponge. Any
protist, fungi,
plant, or animal /
human
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Prokaryotes are a group of organisms that lack
a nucleus or any other membrane-bound organelles.
Certain structures found in prokaryotes not found ineukaryotes are flagellum, a nucleoid, and a capsule.
They lack a true membrane bound nucleus.
Eukaryotes are organisms that contain a
nucleus, nuclear envelope, which sets them apart
from prokaryotes. Cell division tends to be different
between eukaryotes and prokaryotes. Eukaryotes go
through mitosis and meiosis. All Eukaryotes have
true nucleus and membrane system in the
cytoplasm.
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The cells of all prokaryotes andThe cells of all prokaryotes andeukaryotes possess two basiceukaryotes possess two basic
features: a plasma membrane andfeatures: a plasma membrane and
cytoplasm. cytoplasm. However, the cells of However, the cells of
prokaryotes are simpler than thoseprokaryotes are simpler than thoseof eukaryotes. of eukaryotes.
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The major similarities between the twoThe major similarities between the two
types of cells (prokaryote andtypes of cells (prokaryote and
eukaryote) are:eukaryote) are:
They both have DN A as their genetic material. They are both membrane bound.
They both have ribosomes .
They have similar basic metabolism . They are both amazingly diverse in forms.
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Generalization:
Prokaryotic cells lack a nucleus; the wordprokaryotic means ³primitive nucleus.´ Eukaryotic
cells, on the other hand, have a distinct nucleus.
The nucleus of eukaryotic cells is composedprimarily of protein and deoxyribonucleic acid, or
DN A. The DN A is organized into linear units
called chromosomes, also known as chromatin
when the linear units are not obvious. Functionalsegments of the chromosomes are referred to as
genes.
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Approximately 100,000 genes are
located in the nucleus of all humancells. Although prokaryotic cells have
no nucleus, they do have DN A. The
DN A exists freely in the cytoplasm as aclosed loop. It has no protein to support
it and no membrane covering it. A
bacterium typically has a single loopedchromosome with about 4,000 genes.