Cytoplasmic Organelles I PDF

Cytoplasmic Organelles I By: Dr. Moustafa Al Sawy Dr. Shaimaa Mohamed Amer MBBCH, M.SC. M.D HISTOLOGY MBBCH, M.SC. M.D HISTOLOGY Associate Professor of Histo...

Cytoplasmic Organelles I By: Dr. Moustafa Al Sawy Dr. Shaimaa Mohamed Amer MBBCH, M.SC. M.D HISTOLOGY MBBCH, M.SC. M.D HISTOLOGY Associate Professor of Histology & Cell Biology Associate Professor of Histology & Cell Biology Certified Medical Educator Intended Learning Outcomes (ILOs): Knowledge : By the end of the lecture , each student will be able to: 1.Outline microscopic feature of the eukaryotic cell. 2.Describe the electron microscopic features of the plasma membrane. 3. Enumerate membranous & non –membranous cytoplasmic organelles. 4.Describe LM & EM and mention functions of (cell membrane, mitochondria & Golgi body).  Cytology Cytology means study of cells which is the structural & functional unit of the body. The cell Definition: It is the structural & functional unit of all living tissues. *Cells have different shapes ( flat, cubical, columnar, rounded or irregular ) & sizes. *Lymphocytes is the smallest while fat cells & ova are the largest cells. Structure of cell Cytoplasm Nucleus Organelles Inclusions Living Nonliving Permanent Temporary Essential Not essential Active Inert as glycogen & lipids  The Cytoplasmic Organelles (A) Membranous (B) Non-membranous Cell membrane. Free ribosomes & polysomes. Mitochondria. Rough endoplasmic reticulum. Microtubles. (rER) Smooth endoplasmic reticulum. (sER) Filaments. Golgi apparatus. Centrioles, cilia & flagella Lysosomes. Peroxisomes. Light Microscope  1. Cell (Plasma) Membrane Site : Each cell is bounded by a very thin cell membrane. It is also known as plasma membrane , plasmalemma or unit membrane The cell membrane encloses the cellular contents and regulates transport of substances. Structure: By LM, cell membrane is invisible. By EM: *At low magnification it appears as a dense thin line 7.5 - 10 nm in thickness. * At High magnification, it appears as two electron-dense lines (dark) separated by an electron-lucent intermediate zone (light). Therefore, it has a characteristic trilaminar..Chemical composition (molecular biology (The fluid-mosaic theory) The cell membrane is composed of: A- Lipids (30 %), B- Proteins (60 %) C- Carbohydrates (10 %).  A- The lipid components 1- Phospholipids bilayer. 2- Cholesterol. Each phospholipids molecules have: Polar hydrophilic phosphate heads Non-polar hydrophobic tails of long fatty acid chains Cholesterol molecules: Fill the gaps between the fatty acid tails  B- The protein components 1- Intrinsic (integral transmembrane) proteins: extend across lipid bilayer & protrude from both surfaces. 2- Extrinsic (peripheral) proteins: they stick on the surface (either inside or outside of cell)  C- The carbohydrates Present on the external surface of cell membrane. It consists of short chains of polysaccharides. They are conjugated mainly with membrane proteins to form glycoprotein to some of the membrane lipids to form glycolipids. Form the cell coat.  The cell coat ( glycocalyx) *It is a layer of glycoprotein & glycolipid, on the external surface of the cell membrane. Functions of the cell coat: 1-It plays a role in immunological specificity, contains blood group antigens, has receptor sites, hold the cells together. 2- It shares in the formation of the basement membrane of epithelial tissues and acts as a protective mechanical barrier.  Functions of the cell membrane 1- Protect the structure integrity of the cell. 2- Regulating cell-cell interactions. 3- Recognition of antigens, foreign cells via receptors. 4- Phagocytosis, pinocytosis, and exocytosis. 5- Controlling movements of substances in and out of the cell (selective permeability).  Transport of materials through cell membrane 1. Passive transport 2. Active transport 3. Bulk transport A. simple diffusion Na/K A. Endocytosis Water Phagocytosis Gases Pinocytosis B. Facilitated diffusion B. Exocytosis fat insoluble a) Endocytosis: 1.Phagocytosis (cell eating); engulfed particle is solid & Phagosome is formed. 2.Pinocytosis (cell drinking); engulfed particle is liquid & form pinocytic vesicle. 3.Receptor mediated endocytosis; highly selective process need specific receptors Internally the endosytotic vesicles become associated with special protein called clathrin. b) Exocytosis: Movement of large molecules from inside to outside the cell as extrusion of residual bodies.  2- The Mitochondria Site & Size - Vary in Number & Size. Str u c tur eo f Mit ocho ndri a - Move, divide as it has its own small circular DNA, ribosomes, mRNA, tRNA and systems for protein synthesis independent of the cell nucleus. So, it can divide independently. Structure *LM Rods, granules or filaments. EM: They are enclosed by two membranes; each one has the trilaminar unit membrane. 1.Outer smooth membrane contains specialized transport proteins such as porin, which allow free permeability to molecules to and from the cytosol. 2.Inner membrane *It is thrown into folds, called cristae to increase the surface area and is the location of respiratory chain enzymes, as well as ATP synthetase. *It is highly impermeable to small ions. 3. The cavity is filled with mitochondrial matrix rich in oxidative enzymes together with dense granules that can store the Ca+.  Functions of the mitochondria: *Responsible for energy (ATP) production needed by the cell. So, it considered the power-house of the cell (respiratory apparatus of the cell). *Their number is increased in cells of high metabolic activity e.g. liver cells (2000 in each cell). It supplies the cell with the needed energy (ATP).  Medical Application Abnormal mitochondrial DNA leading to failure of oxidative metabolism that impair mitochondrial function especially in highly needed energy cells as muscle and nervous cells. The most common patterns of clinical disease are: Muscle weakness (Mitochondrial myopathy), particularly affecting the extra ocular muscles. Degenerative disease of the central nervous system (e.g. loss of the optic nerve fibers, loss of cerebellar tissue or degeneration of brain white matter). Metabolic disturbances, by accumulation of high levels of lactic acid. *Such diseases is maternally inherited and may manifest at any age from childhood into adult life. *The diagnosis can be assisted by muscle biopsy, and analysis of mitochondrial DNA.  Subtypes of mitochondrial myopathies MELAS: characterized by mitochondrial encephalomyopathy, lactic acidosis, recurring stroke- like episodes Other findings include Muscle weakness Tonic-clonic seizures MERRF: characterized by myoclonic epilepsy with ragged red fibers destruction of important proteins involved in oxidative phosphorylation Other findings include Generalized seizures  3-Golgi Body Site: Membranous cytoplasmic organelle, between nucleus & periphery. It is the secretory apparatus of the cell. Structure: *LM *Negative Golgi Image: H&E staining of intensely basophilic cells (e.g plasma cells), *Golgi can be seen after special techniques. e.g. silver stain, it appear as a darkly staining granules & fibrils.  3-Golgi Body *E/M 1- Flattened vesicles *They are consisting of elongated parallel sacs piled one upon the other to form Stacks. *Each has an inner concave surface (trans, mature) facing the cell surface and outer convex surface (cis, forming, immature) facing the cell base. *They are the sites of protein concentrations. 2- Transfer vesicles (microvesicles): 3- Macrovesicles (Condensing Vacuoles): *They are large distended vesicles separate from the They carry the formed protein from the rough periphery of mature face of flattened vesicles. endoplasmic reticulum to the outer convex *Condensing vacuoles mature into secretory vesicles or surface of the flattened vesicles. secretory granules through concentration of secretory materials within the vacuoles. *They either discharge their enzymes outside the cell (zymogen granules) or remain in the cell as lysosomes. Golgi apparatus  Function of Golgi Apparatus 1- Packaging and storage of proteins. 2- Adding of CHO, glycogen or phosphate to proteins (modification of proteins). 3- Formation of secretory proteins. 4- Renewing of the cell membrane. 5- Formation of lysosomes.  Case Scenario A 32-year-old woman comes to the physician for genetic consultation. She has a history of recurrent generalized seizures, diffuse muscular weakness, and multiple episodes of transient left-sided paresis. She has been hospitalized several times for severe lactic acidosis requiring intravenous fluid hydration. Her 10-year-old daughter also has seizures and muscle weakness. Her 7-year-old son has occasional muscle weakness and headaches but has never had a seizure. Pathologic examination of a biopsy specimen from the woman's soleus muscle shows ragged-appearing muscle fibers. Genetic analysis of the patient's son is most likely to show which of the following? A) Silenced paternal gene copy B) Heterogonous mitochondrial DNA C) Mutation in DNA repair gene D) Genetically distinct cell line G) Altered allele on X chromosome Any Questions?  References: 1.Basic Histology: Text & Atlas. Editor: Luiz Carlos Junqueira, MD, PhD; Jose Carneiro, MD, PhD. 14th Ed, chapter 2. 2.Wheatear’s functional histology. A text & color atlas.15th Ed. 3.AMBOSS platform Thank You