1. Cell Organelles
Continuo……..

2. 5)- Peroxisomes: generate and degrade H2O2 in performing various metabolic functions
Peroxisomes contain enzymes that transfer hydrogen from various substrates to oxygen
An intermediate product of this process
is hydrogen peroxide (H2O2), a poison,
but the peroxisome has another enzyme
that converts H2O2 to water.
Some peroxisomes break fatty acids down
to smaller molecules that are transported to
mitochondria for fuel.
Others detoxify alcohol and other harmful
compounds. Thus, it exists extensively in
the liver cells

3. The Cytoskeleton الهيكل الخلوى
Microtubules and microfilaments
The Cytoskeleton الهيكل الخلوى
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
Pages

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

5. Cytoskeleton A-Microtubules & filaments
Microfilaments
Intermediate
filaments
Microtubules
Thick
Thin
Middle
سميكة
رفيعة
متوسطة
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)
Page

6. Page 127

7. The Cytoskeleton الهيكل الخلوى Cytoskeleton provide structural support to the cell, and also functions in cell motility and regulation
The cytoskeleton provides mechanical support and maintains shape of the cell.
The cytoskeleton is dynamic, dismantling in one part and reassembling in another to change cell shape.
The cytoskeleton also plays a major role in cell motility by interacting with motor proteins.
In cilia and flagella motor proteins pull components of the cytoskeleton past each other.
This is also true in muscle cells.
Fig. 7.21a, Page 126

8. The Cytoskeleton الهيكل الخلوى Cytoskeleton provide structural support to the cell, and also functions in cell motility and regulation
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.
Motor molecules also carry vesicles or organelles to various destinations w إلى أماكن مختلفة provided by the cytoskeleton.
Fig. 7.21b, Page 126

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

10. During cell division the centrioles replicate.
In many cells, microtubules grow out from a centrosome near the nucleus.
In animal cells, the centrosome has a pair of centrioles, each with nine triplets of microtubules arranged in a ring.
During cell division the centrioles replicate.
Fig. 7.22, Page 128

11. Cilia and Flagella
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.
Cilia usually occur in large numbers on the cell surface.
Flagella usually occur in just one or a few per cell.
Cilia move more like oars مجادبف with alternating power and recovery strokes.
Flagella have an undulatory movement حركة تموجية.
So, They differ in their beating pattern أسلوب الحركة.
Fig. 7.23, Page 129

12. cilia
flagellum

13. 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 structure of cilium and flagellum is identical to that of centriole.
Fig. 7.24

14. 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

15. Thus, Many prokaryotes are motile
About half of all prokaryotes are capable of directional movement الحركة الموجهة by the following:-
By the flagella الأســواط, scattered مبعثرة over the entire surface, is the most common شائعة method of movement.
By two or more filaments خيوط.
By threads خيوط that anchors تربط the cells to the substratum السطح الذى تعيش عليه.
Fig. 27.7, Page 530
Page 529

16. In uniform environment بيئة متجانسة, a flagellated cell may wander randomly.
In a heterogenous environment بيئة مختلطة, many prokaryotes are capable of taxis حركة موجهة, movement toward or away from a stimulus عامل مؤثر. There are two kinds of taxis:
Chemotaxis, تحت تأثير كيميائى حركة موجهة : movement toward the source (positive chemotaxis) or away (negative chemotaxis).
Phototaxis تحت تأثير ضوئى حركة موجهة : movement toward the source of light (negative or positive).

17. 7- Cell membrane
The plasma membrane functions as a selective barrier that allows passage of oxygen, nutrients, and wastes for the whole volume of the cell.
Fig. 7.6, Page 113, and Fig Page 133

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

19. Prokaryotes Eukaryotes
Comparison between Prokaryotes and Eukaryotes
Term
Prokaryotes
Eukaryotes
Size
1-10 um in diameter
um in diameter
Cell wall
Existed
In 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 absent
All are existed
Cell division
By Binary Fission
Meiotic and/or Mitotic