بسم الله الرحمن الرحيم

1. بسم الله الرحمن الرحيم

2. THE CELL

3. The cell • The cell is the basic unit of the organism. • Similar or related cells are grouped to form the tissue. • There are 4 basic tissues (epithelial, connective, muscular and nervous). • The tissues are assembled to form the organs. • Organs are collected to form the systems

6. Cytosol (cytoplasmic matrix) • It fills the spaces between the organelles and inclusions. • It contains enzymes, soluble proteins, nutrients and precursors of macromolecules. • It contains the microtubular lattice that holds the organelles in their position in the cytoplasm.

7. Divisions of Organelles

8. Membranous organelles • Cell membrane. • Mitochondria. • Rough-surfaced endoplasmic reticulum. • Golgi Apparatus. • Secretory vesicles. • Lysosomes and Endosomes. • Peroxisomes. • Smooth-surfaced endoplasmic reticulum.

9. Non-membranous organelles • Free Ribosomes. • Polysomes.

10. The Cell Membrane • 7-8 nm thick. • Not visible by light microscope (LM), but appears trilaminar membrane by EM. • Is formed from two layers separated by thin space. • Molecular components of the cell membrane: • Phospholipid and glycolipid. • Proteins: peripheral and integral. • Cholesterol. • Carbohydrate.

11. The Cell Membrane • Maintain the structural integrity of cell. • Control movement of substances in and out of the cell. • Regulate cell-cell interaction. • Recognition of outer environments. • Interface between cytoplasm and extracellular environments. • Transport system of some molecules.

12. The Mitochondria • By LM, appear as thin threads. • By EM, flexible rod-shaped organelles. • 0.5 - 1 x 7 micron and may reach to 2000 in one liver cell. • It has smooth outer and folded inner membranes, these folds called cristae. • Between membranes are the intermembranous space. • Matrix space lies between the cristae

13. The Mitochondria • The matrix space contains proteins which form the enzymes responsible for Krebs cycles and degradation of fatty acids. • It also contains mitochondrial ribosomes, RNA, DNA and electron-dense matrix granules formed of calcium ions.

14. Functions of Mitochondria • Production of energy by oxidative phosphorylation of ADP to ATP. • Regulation of calcium level in the cytoplsm.

15. Golgi Complex • By EM, appear as parallel flattened saccules arranged in stack. The saccules are formed of smooth single membrane devoid of ribosomes. • It has cis face (facing the RER) and small transfer vesicles. • It has trans face (at the top of the satck) and large secretory vesicles. • And medial compartment between them.

16. Functions Golgi Complex • Modification of protein synthesized in RER. • Packaging and distribution of proteins to the different secretory vesicles and lysosomes. • Sorting out the membrane constituents and regulating where they go (cell membrane or in stored vesicles.

17. Secretory Vesicles • The trans side of the Golgi saccules distend to form presecretory granules which bud off when their contents become condensed to form the secretory vesicles. • Secretory products are released at the cell surface by exocytosis. • Some vesicles are not discharged and form lysosomes.

18. Lysosomes • They are rounded membranous vesicles containing different types of acid hydrolases such as: sulphatases, proteases, nucleases, lipases and glycosidases. • They function in digestion macromolecules, phagocytosed microorganisms, cellular depris and aged organelles such as mitochondria and RER. • Some vesicles are not discharged and form lysosomes.

19. PEROXISOMES • They are small spherical membranous organelles containing oxidative enzymes. • They are concerned with reactions which produce or break down hydrogen peroxide. • Hydrogen peroxide used in killing phagocytosed bacteria and breaking down fatty acids.

20. Smooth Endoplasmic Reticulum • They are a system of anastomosing and branching membranous tubules that lack ribosomes at their external surface. • Their functions are: • Synthesis of concerned steroid, cholesterol and triglycerides. • Detoxification of drugs. • Muscle contraction (sarcoplasmic reticulum)

21. Free Ribosomes and Polysomes • Under LM, free ribosomes appear as diffuse cytoplasmic basophilia. • They may aggregate together to form the polysomes. • They synthesize the proteins of cytoplasmic matrix and nucleus and some mitochondrial proteins

22. Cytoskeleton • Is the internal cytoplasmic support system that controls and maintain the shape of the cell. • It consists of microtubule and filaments.

23. Microtubules • Sites of microtubules: • Centrioles. • Cilia. • Flagella. • Mitotic spindles • Function of microtubules: • Change in cell shape. • Movement of the cell organelles and vesicles. • Control movement of chromosomes.

24. Filaments • Types of filaments: • Thin filament: actin in muscle. • Intermediate filament: neurofilament. • Thick filament: myosin. • Function of filaments: • Give 3 dimentional support to the cell. • Allow shortening of the muscle fibers.

25. Cytoplasmic inclusions • Stored food: • Glycogen. • Lipid. • Pigments: • Exogenous: carotine, carbon particles. • Endogenous: hemoglobin, hemosiderin, bilirubun, melanin and lipofuscin.

26. The Nucleus • Nuclear envelop. • Nuclear chromatin. • Nucleolus.