1 Cell Organelles Continuous……..

2 Microtubules and microfilaments The Cytoskeleton الهيكل الخلوى Pages A network of fibresrovide structural support تدعيم to the cell. The cytoskeleton also functions in cell motility تحرك الخلية and regulation A network of fibres شبكة من الالياف that provide structural support تدعيم to the cell. The cytoskeleton also functions in cell motility تحرك الخلية and regulation

3 The cytoskeleton is a network of fibers extending throughout تمتد عبر the cytoplasm.The cytoskeleton is a network of fibers extending throughout تمتد عبر the cytoplasm. The cytoskeleton organizes يرتب the structures and activities of the cell.The cytoskeleton organizes يرتب the structures and activities of the cell. The Cytoskeleton الهيكل الخلوى Fig. 7.20, 126

4 Cytoskeleton Page Responsible for cell motility, and separation of chromosome during cell division. () (Tubulin protein) Support cell motility and transport materials within the cell. () (Actin protein) Reinforcing the cell shape and fixing position of organelles. () (Fibrous protein) Microfilaments Intermediatefilaments Microtubules ThickThinMiddleسميكة رفيعةمتوسطة أنيبيبات دقيقة ألياف دقيقة ألياف متوسطة

5 Page 127

6 The cytoskeleton provides mechanical support and maintains shape of the cell.The cytoskeleton provides mechanical support and maintains shape of the cell. The cytoskeleton is dynamic, dismantling يتفككin one part and reassembling يتجمعin another to change cell shape.The cytoskeleton is dynamic, dismantling يتفككin one part and reassembling يتجمعin another to change cell shape. The cytoskeleton also plays a major role in cell motility حركة الخلية by interacting with motor proteins البروتين الحركىThe cytoskeleton also plays a major role in cell motility حركة الخلية by interacting with motor proteins البروتين الحركى. –In cilia and flagella motor proteins pull components of the cytoskeleton past each otherعكس بعضهم. –This is also true in muscle cells. Fig. 7.21a, Page 126 The Cytoskeleton الهيكل الخلوى

7 Interactions of motor proteins and the cytoskeleton circulates materials within the cell.Interactions of motor proteins and the cytoskeleton circulates materials within the cell. The cytoskeleton may transmit mechanical signals that rearrange the nucleoli and other structures.The cytoskeleton may transmit mechanical signals that rearrange the nucleoli and other structures. Motor molecules also carry vesicles or organelles to various destinations إلى أماكن مختلفة provided by the cytoskeleton.Motor molecules also carry vesicles or organelles to various destinations w إلى أماكن مختلفة provided by the cytoskeleton. Fig. 7.21b, Page 126 The Cytoskeleton الهيكل الخلوى

8 Microtubule Motor Protein Organelle P Energy Microtubules functions as tracks قضيب that guide motor proteins carrying organelles to their destination. Microtubules functions as tracks قضيب that guide motor proteins carrying organelles to their destination المكان المستهدف. They move chromosomes during cell division

9 Fig. 7.22, Page 128 In many cells, microtubules grow out from a centrosome الجسم المركزى near the nucleus.In many cells, microtubules grow out from a centrosome الجسم المركزى near the nucleus. In animal cells, the centrosome has a pair of centrioles, each with 9 triplets of microtubules تسعة مجموعات كل منها مكون من ثلاثة أنيبيبات (9 + 0 pattern ) arranged in a ring مُرتبة دائريا.In animal cells, the centrosome has a pair of centrioles, each with 9 triplets of microtubules تسعة مجموعات كل منها مكون من ثلاثة أنيبيبات (9 + 0 pattern ) arranged in a ring مُرتبة دائريا. During cell division the centrioles replicate تتضاعف.During cell division the centrioles replicate تتضاعف.

10 Microtubules are the central structural supports both cilia الأهداب and flagella الأسواط. –Both can move unicellular and small multicellular organisms by propelling water outside the organism. Fig. 7.23, Page 129 Cilia and Flagella Cilia usually occur in large numbers on the cell surface.Cilia usually occur in large numbers on the cell surface. Flagella usually occur in just one or a few per cell.Flagella usually occur in just one or a few per cell. Cilia move more like oars مجادبف with alternating power and recovery strokes.Cilia move more like oars مجادبف with alternating power and recovery strokes. Flagella have an undulatory movement حركة تموجية.Flagella have an undulatory movement حركة تموجية. So, They differ in their beating pattern أسلوب الحركة.So, They differ in their beating pattern أسلوب الحركة.

11 cilia flagellum

12 Fig  Both cilia and flagella have the same ultrastructure التركيب الدقيق.  Both have a core مركز of microtubules sheathed by the plasma membrane.  9-doublets (9 + 2 pattern) تسعة مجموعات كل منها مكون من أنيبيبتان of microtubules arranged around a pair at the center.  Flexible “wheels” of proteins connect outer doublets to each other and to the core.  The outer doublets are also connected by motor proteins.  The structurecilium and flagellum is identical to that of centriole.  The structure of cilium and flagellum is identical to that of centriole.

13 Cilia and flagella are formed of arms of a motor protein (dynein بروتين الداينين ).Cilia and flagella are formed of arms of a motor protein (dynein بروتين الداينين ). –Dynein arms alternately grab, move, and release the outer microtubules. –Protein cross-links limit sliding and the force is expressed as bending إلتواء. Fig. 7.25

14 About half of all prokaryotes are capable of directional movement الحركة الموجهة by the following:- 1.By the flagella الأســواط, scattered مبعثرة over the entire surface, is the most common شائعة method of movement. 2.By two or more filaments ألياف. 3.By threads خيوط that anchors تربط the cells to the substratum السطح الذى تعيش عليه. 4.By cilia أهداب that differ from flagella in beating pattern Thus, many prokaryotes are motile متحركة Fig. 27.7, Page 530 Page 529

15 7- Cell membrane Fig. 7.6, Page 113, and Fig Page 133 The plasma membrane functions as a selective barrier حاجز إختيارى that allows passage of oxygen, nutrients, and wastes for the whole volume of the cell.The plasma membrane functions as a selective barrier حاجز إختيارى that allows passage of oxygen, nutrients, and wastes for the whole volume of the cell.

16 Cell membrane Composed of lipids (phospholipids) and proteins Lipid layer contains hydrophilic and hydrophobic regions Phospholipid Hydrophilic مُحب للماء Hydrophobic كاره للماء Proteins Carbohydrate chains Fig. 7.6 Page 113, and Fig Page 138

17 Term ProkaryotesEukaryotes Size1-10 µm in diameter µm in diameter Cell wallExistedIn plant cell ( not animal cell ) nucleus No nuclear envelope but Nucleoid True nucleus exists with nuclear envelope DNA As fibre in the nucleoid region ( plasmids in some cases ) As Chromatin ( DNA and protein ) Specialized Organells Most of them are absentAll are existed Cell division By Binary FissionMeiotic and/or Mitotic Comparison between Prokaryotes and Eukaryotes