Cell Structure [Report in Botany IV]

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)



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.



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.



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.



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.



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.



Two Regions of ProtoplasmTwo Regions of Protoplasm

1. Cytoplasm ± protoplasm outside

the nucleus.

2. Karyoplasm or Nucleoplasm ±

protoplasm inside the nucleus.



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).



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 .



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.



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.



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.



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.



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.



-- 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.



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.



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.



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

.



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.



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.



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.



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).



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.



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.



-- 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.



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 .



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

.



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).

).



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.



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



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.



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 .



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.



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).



-- 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)



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.



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.



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



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



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



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



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



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



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.



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.



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.



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.



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.

Cell Structure [Report in Botany IV]

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