Cell Biology: Structure & Function (PDF)

Cytology DR\HEBA ABD ALRAZAK Lecturer of Histology October 6 university Objectiv -eDefine the cell -Structure & function of cell membrane -Structure & function of mitochondria -Structure & function of endoplasmic reticulum -Structure & function of Golgi apparatus -Structure & funct...

Cytology DR\HEBA ABD ALRAZAK Lecturer of Histology October 6 university Objectiv -eDefine the cell -Structure & function of cell membrane -Structure & function of mitochondria -Structure & function of endoplasmic reticulum -Structure & function of Golgi apparatus -Structure & function of lysosome - Cell The cell is the functional & structural unit of all living tissues. - The cell is the smallest living structure which has vital properties such as growth, secretion, excretion, digestion, contraction, respiration & reproduction. - The cells of the body are variable in shape, size& functions but they are similar in composition: I. Cytoplasm. II. Nucleus.  cell cytoplasm nucleus Inclusion Organelles They are non- They are permanent minute living structures that are living temporary essential for the vital structures, not processesof all cells e.g. essential for the respiration, secretion,  organelles Membranous Non membranous 1-Cell membrane 1) Ribosomes 2-Mitochondria (2) Cytoskeleton 3-Endoplasmic reticulum A- microtubules 4-Lysosomes Centriole –cilia-flagella 5-Golgi apparatus B- Filamentous structure 6-Peroxisome Thin-intermediate-thick Cell membrane Definition: It is membranous organelles. L.M: Not seen under light L.M seen by special stain Ag, PAS stain very thin(8-10nm). E.M: Two dark thin layer separated by light one.(trilamellar membrane), outer covering rich with carbohydrates called cell coat  Structures of Cell Membrane (Microbiology) ♠Lipid 30%: Phospholipid 2 layers: Polar end (Hydrophilic) Directed out ward & toward cytoplasmic surface carry charge ,Lipid component of the cell membrane allows passage of fat soluble substances through it. Non polar end (Hydro phobic) to directed inward not charged Cholesterol Incorporated with non-polar end. ♠ Proteins 60%: Integral (intrinsic) Protein: Formed of large and small protein large one can trans membrane the cell membrane at both side act as path way for water soluble substance. Peripheral (extrinsic) protein: Small proteins present on extra or intra cellular (both) surface of cell membrane non continuous. ♠ Carbohydrates 10%: Short poly saccharides chain Present on lipid  Glyco lipid and Present on integral proteinGlyco proteins both forming (cell coat) or glycocalex. Functions of the cells membrane: I-Allow passage of substance: 1 Simple Transport: (1) Passive transport (water, salt)molecules cross according to concentration gradient. (2) Facilitated transport (need carrier intrinsic protein)eg: glucouse 2 Active Transport: Need energy cross against to concentration gradient e.g : Sodium pump at polarizing cell 4- Selective permeability: By presence of receptors 3Bulk Transport (vesicular transport): macromolecule enter & leave cell by vesicular transport through cell membrane By exocytosis or endocytosis cytoplasmic extension: A-Endocyosis: In which substances enter the cell. (1) Phagocytosis: Cell engulf large particle Bacteria, virus to Protect cell. (2)Pinocytosis: Cell pass fluids and water in to cell B-Exocytosis: substance leave outside cell II-Surface Coat : it is glycolipid and glycoprotein Site Outer Surface of cell membrane ONLY Functions of Surface Coat: (1)Recognition. (2)Cell Immunity (3)adhesion III- Keep internal composition of cell.  Mitochondria Definition:Membranous organelles in cell. Responsible for respiration & energy production. Number and sits: It varying in number and function and development according to activity of cell not found at RBCs ,present in liver cells liver cells contain 1000- 2000/ cell. L.M:Seen after staining with iron haemolaxylin & janus green appear as rods, granules or filaments E.M: appear as vesicle rounded or oval in shape covered with double membrane E.M: appear as vesicle rounded or oval in shape covered with double membrane (1) Outer Smooth Layer (2) Inner Incomplete layer and alternating shelves (cristae) increase surface area for deposition of enzymes for oxidative phosphorylation. (3)Matrix: Contain: lipid protein carbohydrate, (A) Oxidative Enzymes. (B) Matrix granules is phosphor lipoprotein bind Ca, Mg (C) DNA,RNA for mitochondrial replication. Functions: (1)Production of energy. (2)Responsible for cell respiration. (3)Responsible for mitochondrial replication.  Endoplasmic Reticulum A) Smooth endoplasmic reticulum B) Rough endoplasmic reticulum  ( Granular Endoplasmic Reticulum) Rough Endoplasmic Reticulum Definition: It is membranous organelles protein forming cell.eg. Plasma cell, fibroblast. It is varying in number size development according to type of cell. L.M: It appears as basophilic area due to ribosomes. E.M: It appears as membrane bounded tubules vesicles or cisternae, sheets on it ribosomes.  Functions:- (1)Responsible for protein synthesis. (2)Condensation and packing of proteins. (3)Transfer of protein to Glogi apparatus. (4)Intra cellular pathway of protein to Golgi apparatus or cell. (5)Share in formation of lysosome by formation of hydrolytic enzyme  (A granular Endoplasmic Reticulum) Smooth Endoplasmic Reticulum Definition: It is membranous organelles of cell. L.M: Not seen ( not demonstrated) (no Ribosomes). E.M: Appears as membrane bounded tubules or vesicles surrounded with smooth membrane. Functions (1)Synthesis and storage of lipid and cholesterol. (2)Synthesis of steroid hormone (3)Storage and formation of glycogen in muscle and liver. (4)In liver it responsible for detoxification of drugs and hormones. (5)In muscle responsible for contraction (Ca pump). (6)Transfer lipid and cholesterol to Golgi apparatus. (7)Intra cellular pathway of lipid to Golgi apparatus.  Golgi apparatus Definition: It is membranous organelles considered as secretory system well developed in protein forming cells and secretory cells. L. M: Golgi apparatus networks of fibrils staining with silver stain. When cell stained with haematoxylin and eosine Golgi apparatus not stained Give Golgi negative image.  Golgi apparatus present between nucleus and secondary pole of cell in nerve cells it surrounds the nucleus(perinuclear).  E. M: It appears as suecer shape flattened vesicles stacked over each other.  It has 2 faces. (1)Convex Face (Forming)( immature) (cis) facereceive transfer vesicles as protein from RER (2)Concave Face :(Mature face) secretory vesicles come out carrying condensed& modified protein Function: (1)Concentration of proteins and lipid from rough and smooth endoplasmic reticular. (2)Modification of proteins and lipid by coupling to carbohydrates. (3)Secretion of modified material may be hormones or enzymes (secretory vesicles). (4) Isolation and packing of hydrolytic enzymes in lysosomes, (5) Production and maintenance of cell membrane.  Lysosomes Definition: Membranous organelles rich in hydrolytic enzymes. considered as the digestive system of the cell. Number: They are numerous in phagocytic cells e.g. white blood cells. Origin: The hydrolytic enzymes are formed in rER &carried in transfer vesicles to Golgi apparatus &come out as primary lysosomes  Lysosomes E.M: Vesicles formed from and enzymes at Golgi apparatus formed of from RER Primary lysosomes: newly formed lysosomes homogenous vesicles surrounded single membrane.  Lysosomes Secondary lysosomes:It is Heterogeneous vesicles. It is primary lysosomes engulf macromolecules (1)Heterolysosomes:Fusion of primary lysosome with bacteria or virus (Phagosomes). (2)Multivesicular lysosome :It is primary fusion of lysosome with pinocytic vesicles. (3)Auto lysosome:fusion primary of lysosome with any old Organelles e.g dead mitochondria. (4)Residual bodies: It is secondary lysosome with undigested ruminants as lipofuscin granules in long lived cells as nerve and cardiac Function of Lysosomes: (1)Digestion of Nutrient materials absorbed by cell. (2)Defensive, destruction of Bacteria, virus (Phagocytosis). (3) Removal of any dreaded organelles. (4)Lysis of deeded cells and body after death (autolysis). (5)Change inactive hormone into active one as thyroid hormone (6)Help sperm to penetrate ovum NUCLEUS NUCLEUS Definition: It is largest and most distinct part of cell. It carries genetic information encoded in DNA of the chromosomes and also newly formed RNA present in all cells except RBC,s platelets (not true cells). L.M: Appears as dark blue basophilic body. 1-Site: Occupy the widest part of the cell (Usually in center, may be eccentric at one side, Or peripheral as fat cells). 2-Number One --- Mononucleatide ---- most of cells Two--- Binnucleated ---- liver cells Multi ---- Multi nucleated ---- Osteoclasts, skeletal muscles  3- Size: Small, medium, large. 4- Appearance: -Vesicular: lightly stained (as in nerve cells) -Condensed: darkly stained (lymphocytes) 5- Shape: -Rounded -Oval -Flattened -horse-Shoe (eosinophil) bilobed -Lobulated (Segmented) eg (Neutrophil) - Kidney Shape (Monocyes) Structure of the nucleus Nuclear Membrane Enveloped Chromatin Material Nucleolus Nuclear Sap  Nuclear Membrane envelope LM: Blue Line chromatin on inner surface & ribosomes on outer E.M: Double walled membrane with many pores. *Outer membrane: continuous with endoplasmic reticulum. `*Inner Membrane: continuous with chromatin (Peripheral Chromatin). Nuclear Pores Chromatin Material * Formed mainly of protein+ DNA code of genetic information's. DNA: Double helix around a core of histone. L.M: Basophilic granules may be coarse or fine. E.M : Euchromatin (pale blue by L.M) It is active form (extended).invisible pale by LM HeterochromatinCondensed, inactive, dark nucleus.  Peripheral chromatin (attached by inner nuclear membrane)  Chromatin Island (In Nuclear Sap).  Nucleolus associated chromatin (aggregate to form nucleolus).