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Cell OrganellesCell Organelles

Continuo……..Continuo……..

http://www.northland.cc.mn.us/biology/biology1111/animations/flagellum.html

Microtubules and microfilamentsMicrotubules and microfilamentsThe CytoskeletonThe Cytoskeleton الهيكل الهيكل

ييالخلوالخلو

A network of fibresA network of fibres االلياف من to to تدعيمتدعيم that provide rovide structural supportstructural support شبكةthe cell. The cytoskeleton also functions in the cell. The cytoskeleton also functions in cell motilitycell motility الخلية الخلية تحرك and and تحركregulationregulation

It is made of 3 fiber typesIt is made of 3 fiber types– MicrofilamentsMicrofilaments– MicrotubulesMicrotubules– Intermediate filamentsIntermediate filaments

It has 3 main functions:It has 3 main functions:– provides mechanical support provides mechanical support

of the cell keeps organelles in of the cell keeps organelles in fixed locationsfixed locations

– helps move materials within helps move materials within the cellthe cell

– plays a major role in cell plays a major role in cell motilitymotility

CytoskeletonCytoskeleton

MicrofilamentsMicrofilaments

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CytoskeletonCytoskeleton

Responsible for cell Responsible for cell motility, and motility, and separation of separation of

chromosome during chromosome during cell division.cell division.

((Tubulin protein))

Support cell Support cell motility and motility and

transport materials transport materials within the cell.within the cell.

((Actin protein))

Reinforcing the cell Reinforcing the cell shape and fixing shape and fixing

position of position of organelles.organelles.

((Fibrous protein))

MicrofilamentsMicrofilamentsMicrofilamentsMicrofilamentsIntermediate Intermediate

filamentsfilamentsIntermediate Intermediate

filamentsfilamentsMicrotubules Microtubules Microtubules Microtubules

Thick Thin Middle

سميكةسميكة رفيعةرفيعة متوسطةمتوسطة

أنيبيبات أنيبيبات دقيقةدقيقة

دقيقة دقيقة ألياف ألياف ألياف ألياف متوسطةمتوسطة

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• The cytoskeleton is dynamic, dismantling The cytoskeleton is dynamic, dismantling يتفككيتفككin one part and in one part and reassembling reassembling يتجمعيتجمعin another to change cell shape.in another to change cell shape.

• The cytoskeleton also plays a major role in cell motility The cytoskeleton also plays a major role in cell motility الخلية الخلية حركة حركةby interacting with motor proteins by interacting with motor proteins الحرك الحرك البروتين ييالبروتين ..

• Motor proteins are able to move along the surface of a suitable Motor proteins are able to move along the surface of a suitable substrate (powered by ATP).substrate (powered by ATP).

• Motor proteins are the driving force behind most active transport Motor proteins are the driving force behind most active transport of proteins and vesicles in the cytoplasmof proteins and vesicles in the cytoplasm

Cell MovementCell Movement– Crawling is accomplished Crawling is accomplished

via actin filaments and the via actin filaments and the protein protein myosinmyosin..

– In In ciliacilia and and flagellaflagella motor motor proteins pull components proteins pull components of the cytoskeleton past each of the cytoskeleton past each otherother بعضهم بعضهم عكس . . عكس

– This is also true This is also true in muscle cells.in muscle cells.

Motor proteins

Transport vesicle

Motor proteins

Microtubule

ATP ADP+Pi ATP ADP+Pi

MOTOR PROTEINS "WALKS" ALONG A MICROTUBULE TRACKMOTOR PROTEINS "WALKS" ALONG A MICROTUBULE TRACK

Motor proteins are a class of molecular motors that are able to move along the surface of a suitable substrate. They are powered by the hydrolysis of ATP and convert chemical energy into mechanical work.

• Interactions of motor proteins and the cytoskeleton circulates Interactions of motor proteins and the cytoskeleton circulates materials within the cell.materials within the cell.

• The cytoskeleton may transmit mechanical signals that The cytoskeleton may transmit mechanical signals that rearrange the nucleoli and other structures. rearrange the nucleoli and other structures.

• Motor molecules also Motor molecules also carry carry vesiclesvesicles or or organellesorganelles to various destinations to various destinations

مختلفة أماكن مختلفة إلى أماكن provided by the provided by the إلىcytoskeleton. cytoskeleton.

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MicrotubuleMicrotubule

Motor Protein

OrganelleOrganelle

P

Energy

Microtubules functions as tracks Microtubules functions as tracks قضيبقضيب that guide motor that guide motor proteins carrying organelles to their destination proteins carrying organelles to their destination المكان..المستهدفThey move chromosomes during cell divisionThey move chromosomes during cell division

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• In many cells, In many cells, microtubulesmicrotubules grow out from a grow out from a centrosomecentrosome الجسم الجسم

ييالمركزالمركز near the nucleus.near the nucleus.

• In animal cells, the centrosome has a pair of In animal cells, the centrosome has a pair of centriolescentrioles, each , each with with 9 triplets9 triplets of microtubules of microtubules أنيبيبات ثالثة من مكون منها كل مجموعات أنيبيبات تسعة ثالثة من مكون منها كل مجموعات )) تسعة 99 + + 00 patternpattern) arranged in a ring) arranged in a ring دائريا دائريا م$رتبةم$رتبة ..

• During cell division the During cell division the centriolescentrioles replicate replicate تتضاعفتتضاعف..

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• Microtubules are the central structural supports both cilia األهداب and flagella األسواط.– Both can move unicellular and small multicellular organisms by

propelling دفع water outside the organism.

Cilia and FlagellaCilia and Flagella

• CiliaCilia usually occur in large numbers on the cell surface. usually occur in large numbers on the cell surface.

• FlagellaFlagella usually occur in just one or a few per cell. usually occur in just one or a few per cell.

• CiliaCilia move more like oars move more like oars مجادبفمجادبف with alternating power with alternating power

and recovery strokes.and recovery strokes.

• FlagellaFlagella have an undulatory movement have an undulatory movement تموجية تموجية حركة ..حركة

• So, They differ in their beating patternSo, They differ in their beating pattern الحركة الحركة أسلوب ..أسلوب

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ciliacilia

flagellumflagellum

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Both Both ciliacilia and and flagellaflagella have the same have the same

ultrastructure ultrastructure الدقيق الدقيق التركيب ..التركيبBoth have a core Both have a core مركزمركز of of

microtubulesmicrotubules sheathed by the sheathed by the

plasma plasma

membrane. membrane. 9-doublets (9-doublets (9 + 2 pattern9 + 2 pattern) ) تسعة تسعة

من مكون منها كل من مجموعات مكون منها كل مجموعات

of of أنيبيبتانأنيبيبتان

microtubules arranged around a microtubules arranged around a

pair at the center.pair at the center.Flexible “wheels” of proteins Flexible “wheels” of proteins

connect outer doublets to each connect outer doublets to each

other other

and to the core. and to the core.The outer doublets are The outer doublets are

also connected by motor also connected by motor

proteins. proteins.The structureThe structure of ciliumcilium

and flagellum is identical and flagellum is identical

to that of centriole. to that of centriole.

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• CiliaCilia and and flagellaflagella are formed of arms of a motor are formed of arms of a motor protein (protein (dynein dynein الداينينالداينين بروتينبروتين ))..

– Dynein arms alternately Dynein arms alternately grab, move, and release grab, move, and release the outer microtubules.the outer microtubules.

– Protein cross-links limit Protein cross-links limit sliding and the force is sliding and the force is expressed as bending expressed as bending إلتواءإلتواء..

http://www.northland.cc.mn.us/biology/biology1111/animations/flagellum.html

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7- Cell membrane7- Cell membrane

• The plasma The plasma

membrane membrane

functions as a functions as a

selective barrier selective barrier

إختيارى إختيارى حاجز that that حاجز

allows passage allows passage

of oxygen, of oxygen,

nutrients, and nutrients, and

wastes for the wastes for the

whole volume of whole volume of

the cell.the cell.

Cell membraneCell membrane

Composed of lipids Composed of lipids (phospholipids) and proteins(phospholipids) and proteins

Lipid layer contains Lipid layer contains hydrophilichydrophilic and and hydrophobichydrophobic regions regions

PhospholipidPhospholipid

HydrophilicHydrophilic حبFحب مFمللماءللماء

HydrophobicHydrophobic للماء للماء كاره كاره

ProteinsProteins

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Term Prokaryotes EukaryotesSize 1-10 µm in diameter 10-100 µm in diameter

Cell wall Existed In plant cell (not animal cell)

nucleusNo nuclear envelope but Nucleoid

True nucleus exists with nuclear envelope

DNAAs fibre in the nucleoid region (plasmids in some cases)

As Chromatin (DNA and

protein)

Specialized Organells

Most of them are absent All are existed

Cell division

By Binary Fission Meiotic and/or Mitotic

Comparison between Prokaryotes and EukaryotesComparison between Prokaryotes and Eukaryotes