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Cell OrganellesCell Organelles

Continuous……..Continuous……..

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The Cytoskeleton الهيكلالخلوى

Pages 126 - 131

A network of fibres االلياف من that provide structural شبكةsupport تدعيم to the cell extending throughout تمتدthe cytoplasmخالل

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Cytoskeleton

Page 126 - 131

Responsible for cell motilityحركة , and

separation of chromosome during cell division انفصال

اثناء الكروموسوماتالخلوي .االنقسام

(Tubulin protein)

Support cell motility and

transport materials within the cell نقل

الخلية داخل .المواد

(Actin protein)

Support the cell shape and fixing

position of organelles.

(Fibrous protein)

MicrofilamentsIntermediate

filamentsMicrotubules

Thick Thin Middleسميكة رفيعة متوسطة

أنيبيبات دقيقة

دقيقة ألياف ألياف متوسطة

4Page 127

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• The cytoskeleton is dynamicمتحرك , dismantling يتفككin one part and reassembling يتجمعin another to change cell shape الخلية شكل . يغير

Functions of the cytoskeleton

1. The cytoskeleton provides mechanical supportدعم and maintains shape of the cell الخلية شكل على . يحافظ

2. The cytoskeleton also plays a major role اساسي دور in cell يلعبmotility الخلية مع by interacting حركة البروتين motor proteins االتصال.الحركى

3. Interactions of motor proteins and the cytoskeleton circulates تدور materials الموادwithin the cell.

4. Motor molecules also carry organelles العضيات to variousتحملdestinations العمل .by the cytoskeleton أماكن

Fig. 7.21a, Page 126

The Cytoskeleton الخلوى الهيكل

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MicrotubuleMicrotubule

Motor Protein

Organelle

P

Energy

Microtubules functions as tracks قضيب that guide motor proteins carrying organelles to their destination المكان.المستهدفe.g. They move chromosomes during cell division

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Fig. 7.22, Page 128

المركزي Centrosomeالجسم

• In animal cells, the centrosome has a pair of centrioles السنتريوالت من each with 9 triplets of ,زوجmicrotubules

• أنيبيبات ثالثة من مكون منها كل مجموعات ) تسعة 9 + 0 pattern) arranged in a ring دائريا .مKرتبة

• During cell division the Centrioles replicate تتضاعف.

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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 الماء .water outside the organism دفع

Fig. 7.23, Page 129

Cilia and Flagella

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

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

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cilia

flagellum

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Fig. 7.24

Both cilia and flagella have the same ultrastructure الدقيق .التركيبBoth have a core مركز of microtubules surrounded by ب محاطة

the plasma membrane. 9-doublets (9 + 2 pattern) أنيبيبتان من مكون منها كل مجموعات of تسعة

microtubules arrangedمرتبة aroundحول a pair زوج at the

centerالمركز.

The outer doublets are

also connected by motor

proteins.The structure of cilium

and flagellum is identical

to that of centriole.

Cilia and flagella are formed

of arms of a motor protein

(dynein الداينين بروتين ).

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7- Cell membrane

Fig. 7.6, Page 113, and Fig. 7.29 Page 133

• The plasma

membrane

functions as a

selective barrier

إختيارى that حاجز

allows passage

of oxygen,

nutrients, and

wastes for the

whole volume of

the cell.

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Cell membrane

Composed of lipids (phospholipids) and proteins

Lipid layer contains hydrophilic and hydrophobic regions

Phospholipid

Hydrophilic م<حبللماء

Hydrophobic للماء كاره

Proteins

Carbohydrate chains

Fig. 7.6 Page 113, and Fig. 7.29 Page 138

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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 Eukaryotes