Lecture 1: The Cell - Human Anatomy

PAS 313: Human Anatomy Lecture 1: Cell 1 Dr. Joseph Costa, PhD Department of Pathology and Anatomical Sciences 1 Chemical Cellular Tissue Smaller & Organ less complex...

PAS 313: Human Anatomy Lecture 1: Cell 1 Dr. Joseph Costa, PhD Department of Pathology and Anatomical Sciences 1 Chemical Cellular Tissue Smaller & Organ less complex Organ System Larger & Organism More complex 2  The Cell The fundamental structural & functional unit of all organisms. Wide variety of shapes and sizes 3 Liver Heart Intestine Bone & blood 4 A. General Structure Although cells are morphologically different, cells have many common characteristics 5  B. Chemical Composition Most Commonly occurring elements In general, all cells contain the following: Oxygen (O) 65% Carbon (C) 18% Hydrogen (H) 10% 1. Inorganic compounds Nitrogen (N) 3% Water (75% of cell mass) Electrolytes (acids, bases, salts) Additional (and important) elements 2. Organic compounds—contain Carbon Calcium (Ca) Potassium (K) Protein (2%, composed of amino acids) Sodium (Na) Phosphorus (P) Magnesium (Mg) Chlorine (Cl) Sulfur (S). 6 Types of Organic compounds 1. Protein Structure and function determined by number & sequence of amino acids. Example of protein functions: Structural: Responsible for cell “form” or “shape” Enzymes: Catalyze chemical reactions Hormones: Act as regulators 7  Types of Organic compounds (cont.) 2. Carbohydrates (CH2O) Monosaccharide: Simple sugar (glucose) Disaccharide: two sugars linked together (sucrose) Polysaccharide: many sugars linked together (glycogen) 8  Types of Organic compounds (cont.) 3. Lipids: Stored as fats Cholesterol Precursor to Fat sol Vitamins and steroid hormones Phospholipids: Major component of cell Cell membrane membrane bilayer (bilayer: 2 layers) 9  Types of Organic compounds (cont.) 4. Nucleic acids DNA (deoxyribonucleic acid) chromosomes, genetic information RNA (ribonucleic acid) Involved in protein synthesis Human chromosome 10 C. Major Components of Cells 1. Cell Membrane (plasma membrane, plasmalemma) Composed of: Lipids (phospholipids) Proteins Carbohydrates General Structure is the Fluid Mosaic Model Current theory for cell membrane arrangement 11 Cell Membrane Functions: 1. Compartmentalize specific regions for cell-to-cell signaling 2. Regulate movement of materials Selectively permeability: Only certain substances pass in or out of cell 12  Phospholipids are amphipathic: 2 Major components 1. Polar Head (positive charge) = Hydrophilic: “water loving” 2. Non-polar Tail (negative charge) = Lipophilic: “lipid loving” 13  The Fluid Mosaic Model Amphipathic phospholipid components arranged in bilayer Membrane almost fluid-like Proteins & carbohydrates “float” like icebergs in sea of phospholipids 14 Cell Membrane 3. Provides for intercellular interactions Communication between cells Place for cell-to-cell adhesions Provides recognition (binding) sites for: Hormones Antibodies Enzymes Other signaling molecules 15  Organelles: Small functional structures within the cell 2. Nucleus A) Structure: dense mass with following components: 1. Contains Chromatin: DNA and protein Chromosome: condensed form in nucleus Chromatid: ½ of duplicated chromosome Both covered in mitosis lecture 2. Nuclear envelope: membrane surrounding nucleus 3. Nucleolus: Site of RNA synthesis 16 b) Nucleus function 1. Stores genetic material 2. Involved in cellular division (mitosis) 3. Regulates cellular metabolism and activity of all organelles 17 3.) Cytoplasm: Substance within the cell a.) Cytosol Fluid w/ in cell Varies in composition depending on cell type b.) Organelles Small structures that perform specific cellular functions Organelles in cytoplasm 18 C. Cytoskeleton Proteins: Maintain cell shape and structure Involved in movement Compartmentalize organelles d. Inclusions Small substance associated with cell function Not organelles E.g. Lipids, pigments, glycogen, etc. 19 b.) Other Organelles 1. Ribosomes “protein factories” of cell Structure: Composed of protein and RNA Function: Site of protein synthesis Cells producing large amounts of protein More ribosomes present 20 b. Organelles 2. Endoplasmic Reticulum Structure Membranous network of channels Located throughout the cytoplasm Continuous with nuclear envelope Function Provides a channel for communication and transport of substances throughout the cell 21 Types of Endoplasmic Reticulum Rough (R.E.R.): Has multiple ribosomes on surface. Responsible for manufacture and transport of protein Smooth (S.E.R.): responsible for lipid production, metabolism, and calcium storage. 22 b.)Organelles 3.) Golgi Apparatus/ Complex Structure Stacks of flattened “sacs” Function Storage of protein Packages materials into vesicles or granules for storage or secretion 23  Golgi apparatus Note the spatial relationship with nucleus and ER 24 b. Organelles 4. Mitochondria: “Powerhouse” of the cell Structure Rod-shaped Has internal folds called cristae Function Cellular respiration Production of energy from ATP for cellular functions 25 c. Cytoplasmic Inclusions Wide variety of chemical substances whose presence varies depending on the type of cell. Secretory granules Hemoglobin Lipid droplets Pigments Lysosomes Peroxisomes Vacuoles 26 d. Cytoskeleton 1. Microtubules Small, hollow tubules which run throughout the cytoplasm. Formed by protein tubulin. Function: Provide cellular framework Serve as conducting channels through which substances pass through the cytoplasm Structural component of centrioles and cilia 27 d. Cytoskeleton 1. Centrosome Located near nucleus 1 or 2 per cell (depend on cell type) houses 2 centrioles centrosome 2. Centrioles Cylindrically shaped organelles Composed of 9 nine triplets of microtubules 2 per cell, located near nucleus BOTH Play important role in cell division 28 d.) Cytoskeleton 3.) Microfilaments Thin strands of protein which are usually found in bundles. Provide “skeletal” support Associated with contractile activities and cell locomotion ( actin / myosin) 29 30 Microfilaments are abundant in muscle cells 31 Surface Specializations 1. Microvilli Structure: Finger-like projections of cell membrane made by in-folding Function: Increase surface area of cell membrane Facilitates transport 32  2. Cilia Structure: Cytoplasmic projections made of microtubules Function: Move in a wave-like fashion to move mucous, etc. 33 e. Surface Specializations 3.) Cellular Adhesions: Junctional complexes; specialized regions of cell-to-cell contact Tight junctions Form tight seal between cells Desmosomes: “Spot-weld” cells together Gap junctions Allow for cell-to-cell exchange and communication 34 Up Next: Cell 2 - Mitosis 35