Cell Biology PDF - Helwan National University

HELWAN NATIONAL UNIVERSITY FACULTY OF SCIENCE BIOTECHNOLOGY & GENETIC ENGINEERING PROGRAM Cell biology First year students 2024-2025  The functional and structural What is the cell ? unit of living organisms It is a unit...

HELWAN NATIONAL UNIVERSITY FACULTY OF SCIENCE BIOTECHNOLOGY & GENETIC ENGINEERING PROGRAM Cell biology First year students 2024-2025  The functional and structural What is the cell ? unit of living organisms It is a unit which surrounded by plasma membrane (plasma lemma) which contains cytoplasm and organisms as mitochondria, lysosomes, endoplasmic reticulum, ribosomes, …etc.  Cell Theory (Schleiden and Theodore Schwann) All organisms are composed of cells Cell is the structural and functional unit of life Cells arise from pre-existing cells Nerve cell Cells vary in shape and size Muscle cell Different human Epithelial cell cells  The main function: it covers and protects the outer (skin) and inner layers of body (as internal organs; small intestine).  It can be modified to performs as specific function as secretion of some substances.  It has several types; squamous, cuboidal and columnar cells. Muscular cells  The main function: it is responsible for movement of body.  It has several types; cardiac muscles (in heart), skeletal muscles and smooth muscles. Nervous cells  The main function: it is responsible for sensation and transportation of nerve impulses.  Neurons (nerve cells) are the functional, building unit of nervous system. EXAMPLES ON DIFFERENT TYPES OF HUMAN CELLS Cuboidal epithelial cells Smooth muscles (covers Neurons or nerve cells (with round and central internal organs, involuntary (formed from soma or body nucleus) movements) and long axon)  Cell modification Any structural or functional What is the cell change in cell that helps it modification ? perform a specific functions Types of cell modification Epithelial cells as Muscle cells as Nervous cells as modified cells modified cells modified cells 1- Epithelilal cells with brush boarders, microvilli Smooth muscle cells in Sensory cells (neurons) 2- Secretory cells internal human organs 3- basket cell  Brush boarders and microvilli Brush boarder Microvillus It is a dense layer of Tiny, finger-like microvilli on the surface projection on surface of of some epithelial cells some epithelial cells  The main function: to increase the surface of absorption in their sites  The location of this structure: as the small intestine and kidney tubules  Ultra-structure of brush boarders and microvilli under electron microscope Microvillus Brush boarder Secondary lysosome  It is a cuboidal epithelial cell Mitochondria with brush boarder (group of microvilli) to increase the surface of absorption. Round nucleus  Mainly it is found in kidney tubules.  Ultra-structure of epithelial secretory cells Rough endoplasmic reticulum (RER) Nucleus  It is a secretory epithelial cells which contains secretory vacuoles which secreted from the rough endoplasmic Mitochondria reticulum (RER).  Main function: secretion of enzymes. Secretory  It is found in stomach faces the vacuoles gastric cavity and releases digestive enzymes.  Ultra-structure of Smooth muscles  Smooth muscles are non-striated and involuntary muscles.  They have elongated nucleus.  They are found in internal organs as stomach and small intestine. Smooth  Main function: it is responsible for myocyte involuntary internal organs. (muscle cell) Elongated nucleus  Ultra-structure of neurons (nerve cells) Nucleus Nucleolus Soma of neuron Nissl’s  Neuron is the functional and structural unit of the bodies nervous system.  It contains group of Nissl’s bodies (group of RER and ribosomes), which produce proteins of neurons.  Ultra-structure of basket cells Nucleus Basket cell Gland  Basket cell is modified epithelial cell that turns to myofibroblast and it becomes contractile cell.  It is found around glands.  Main function: squeezing of glands for excretion  Sensory cells  Sensory cells are specialized cells that detect the stimuli like light, sound, touch or chemicals.  They able to covert the stimuli into nerve impulses for the brain to process.  Examples: 1- photoreceptors (in eyes). 2- mechanoreceptors (in skin). 3- taste cells (on tongue).