1 Microtubules and microfilaments The Cytoskeleton الهيكل الخلوى 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

2 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

3 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.

4 cilia flagellum

5 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.

6 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

7 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

8 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.

9 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

10 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