Cell Biology Course (Bio-1101) Lecture 2: Specialized Cells of Higher Organisms PDF

Cell Biology Course (Bio-1101) Lect. 2: Specialized cells of higher organisms Assoc. Prof. / Reda M. Mansour The Scale of Life Division of Metric Unit  Tools and techniques of Cell Biology A- Histology & using of microtome Fixation: preserve tissues & prevent pos...

Cell Biology Course (Bio-1101) Lect. 2: Specialized cells of higher organisms Assoc. Prof. / Reda M. Mansour The Scale of Life Division of Metric Unit  Tools and techniques of Cell Biology A- Histology & using of microtome Fixation: preserve tissues & prevent post-mortem changes. Embedding: Tissue is infiltrated by Paraffin. A microtome: is a device used for sectioning paraffin- embedded tissues for light microscopy. Staining: Tissues are stained by different stain.  B- Using of Light Microscope (LM): - It uses light that passes through the specimen and glass lenses. The lenses refract (bend) the light as an image magnified into the eye or into a camera. - It can magnifies up to 1000-2000 X (Bright-Field Microscopy) or 400-800 (inverted microscopy) or 5-250 (dissecting microscopy).  1- Bright field light microscopy = Compound microscopy - Light pass from below the specimen (from the bottom) to condenser and to stained specimen on the stage. - Then, light (the image) is collected and magnified by objectives (above the specimens) and ocular lens at the top. Types of lenses: 1- Objective lenses: 4, 10, 40, 100 X. 2- Ocular lenses; 10, 20 X.  Note the positions of Light source, Objectives, ocular lenses, condenser & Stage in each microscope LM Light microscopy of Trachea  2- Inverted microscope - Inverted microscope is a microscope with its light source and condenser on the top, above the stage while the objectives are below the stage. - Importance: It is useful for observing living cells or organisms in a large container (e.g., a tissue culture flask or petri dishes) Inverted Microscope  3- The stereo or dissecting microscope It is designed with a low magnification power (5x-250x), by use of light reflected from the surface of the specimen. It has 2 light sources  3- Electron microscope (EM): It uses a beam of electrons through the specimen or onto its surface. Types of Electron microscopy: 1- Scanning electron microscope (SEM): - It studies surface topography of specimens. - It magnifies up to 30, 000 X. 2- Transmission electron microscope (TEM): - It studies the internal structure of cells. - It magnifies up to 1, 000, 000 X. SEM SEM of Blood cells SEM of different bacterial cells TEM TEM of liver cell  C- Subcellular fractionations All centrifugations should be done at 4°C. Samples should be kept on ice throughout the procedure. - It isolates subcellular organelles to study their structures & functions by biochemical studies. - It occurs through differential centrifugation which is “the separation cell components according to their size and density”. The first step is the disruption of the plasma membrane. Several methods are used: 1- Sonication (exposure to high-frequency sound). 2- Grinding in a mechanical homogenizer. 3- Treatment with a high-speed blender. All these procedures break the plasma membrane and the endoplasmic reticulum into small fragments while leaving other components of the cell (such as nuclei, lysosomes, peroxisomes, mitochondria, and chloroplasts) intact. The suspension of broken cells (a lysate = homogenate) is fractionated into its components by ultracentrifuge, which rotates samples at very high speeds (up to 100,000 rpm = 500,000 times greater than gravity). So, cell components move toward the bottom of tube to form a pellet (sediments) and supernatant (the remaining solution). 1- at 1,000 g, nuclei & cellular debris is sediment into pellet (sediments) & other in supernatant (remaining of solution). 2- at 20,000 g, supernatant is separated into pellet (containing mitochondria, chloroplat, lysosomes & peroxisomes) and supernatant again. 3- 80,000 g, supernatant is separated into pellet (containing fragments of plasma membrane, endomembranes & microsomes) and supernatant again. 4- at 150,000 g, supernatant is separated into pellet (containing microsomes) and supernatant containing cytosol (soluble portion of cytoplasm). Homogenizer Homogenizer Note: A vortex mixer, or vortexer, is a simple device used commonly in laboratories to mix small vials of liquid. Some specialized cells in kingdom Animalia  Examples of eukaryotic cells 1- Circulatory system e.g. erythrocytes (red blood cells), leukocytes (white blood cells), thrombocytes (platelets) 2- Muscular system ( e.g. cardiac, skeletal, smooth muscle fibers) 3- Digestive system (e.g. enterocytes) 4- Urinogenital system (e.g. sperm cells, egg cells) 5- Skeletal system (osteoblast, Chondroblast) 6- Nervous system (neurons)  Some specialized human cells The average adult human body consists of nearly 40 trillion cells. Human body contains over 200 different types of specialized cells. Systems Cells Characteristic Structure Function 1- Integumentary keratinocytes - Stratified squamous Protection & keratin secretion 2- Respiratory Tracheal cells - Ciliated columnar Mucus secretion & Protection epithelium (sweeps up foreign particles. 3- Circulatory Erythrocytes - Biconcave with no nucleus Transport O2 & CO2 and contain hemoglobin Leucocytes - nucleated round cells Defense & Immunity mostly with granules Thrombocytes - Discoid with thread-like Blood clotting appendages 4- Muscular Skeletal cells - Cylindrical, not branched Movement & Contraction Cardiac cell - Cylindrical, branched  Systems Cells Characteristic Structure Function 5- Digestive Enterocytes - Have microvilli Digestive enzymes secretion, absorption Hepatocytes - Polygonal to flat Formation of bile, enzymes, albumin, clotting factors 6- Urinary renal - Simple cuboidal Filtration, ion homeostasis, and epithelium blood pressure control 7- Reproductive Sperm cell - Flagellated cell Carry male genetic material to ovum Egg cell - Oval cell Carry female genetic material & store food 8- Skeletal Osteocytes - Stellate or star-shaped - bone formation or resorption with slender processes 9- Nervous Neurons - Polar with dendrites & - Sensory axons  V.S. in human skin Stratum corneum = Keratinocytes LM of tracheal cells (ciliated columnar epithelia) SEM of tracheal cells with mucous particles (red) & cilia  Blood cells Thrombocytes = LM of human blood smear  Red and white blood cells Erythrocyte Leukocyte SEM of Erythrocytes SEM of erythrocytes, leukocytes, thrombocytes Thrombocytes  In alimentary canal In heart Attached to skeleton wall, blood vessels, Muscle cells LM of liver tissue (hepatocytes) LM of liver tissue (hepatocytes) LM of intestinal tissues(enterocytes) TEM of enterocytes T.S. of bone T.S. of bone T.S. of bone SEM of osteocytes  Sperm cell A mature human sperm cell is composed of: 1- Head: It is spherical consisting of large nucleus and a dome shaped acrosome. Function: it contain the genetic material. The acrosome releases a hyaluronidase enzyme which destroys hyaluronic acid of the ovum and enters into the ovum. 2- Neck: It contains centrioles which gives rise to axial filament (flagellum) of the sperm. 3- Middle piece: It is tubular structure in which mitochondria are spirally arranged. Function: It gives energy to the sperm to swim in the female genital tract. 4- Tail: It contains axial filaments. Function: Tail helps the sperm to swim in the female genital tract (motility). A- SEM of human sperms 1- Sex cells B- SEM of human egg SEM of human egg surrounded by many sperms Neurons  Some specialized cells in kingdom Plantae e.g. 1: Palisade cell (in leaf) contain large vacuole filled with cell sap chloroplast to carry out photosynthesis. e.g. 2: Root cell with root hair to increase the surface area for absorption and anchorage. It contains no chloroplast as there is no light in soil. TEM of palisade cell SEM of Root hairs