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Transcript
Chapter 7: Cell Structure and Function Robert Hooke (1635-1703) • English Scientist • First to use the microscope to observe cells • Coined the term “cell” • Looked at cork cells Anton van Leeuwenhoek 1632-1723 • Dutch scientist • Invented the first compound microscope • First to observe LIVING cells • Blood cells and protists Robert Brown 1773-1858 • Scottish botanist • In 1831 he was the first person to observe the nucleus of a cell Schleiden & Schwann 1804-1881 1810-1882 Developing Cell Theory 1838 • Schleiden • Said “all plants are made up of cells” • Schwann • Said “all animals are made up of cells” Johannes Purkinje Rudolph Virchow • Coined the term • Said “all cells “protoplasm” to arise only from refer to the preexisting jellylike material cells” that fills the cell. Cell Theory Overview 1. All organisms are made of one or more cells. 2. All cells carry on life activities. 3. New cells arise only from other living cells. Prokaryotic vs Eukaryotic • PROKARYOTIC • Simplest form • Lack membrane bound structures • Example: bacteria and some protists • EUKARYOTIC • Most common • Possess membrane bound structures and a nucleus • Found in most living things Sizes of Cells • Eukaryotic are usually larger than prokaryotic • Both nutrients and wastes are constantly entering and exiting cells • Vary in size and shape Cell Structures and Organelles Organelles = specialized internal structures of eukaryotic cells CELL WALL • Found in most bacteria and all plant cells • Gives cell its shape and provides protection • Allows passage of materials • In plant cells, it is made of cellulose • http://www.cellsalive.com/ THE NUCLEUS • Control center or “ city hall ” of cell. • Largest organelle • Controls metabolism and cell reproduction Structure of nucleus • Nuclear envelope = membrane that surrounds the nucleus that acts in manner similar to the cell membrane • Nucleolus = dense are in center of nucleus where DNA,RNA, and proteins are found. *site where ribosomes are produced Picture of nucleus: MICROFILAMENTS • Long, solid, threadlike structures • Made of actin • Involved in muscle contraction and cyclosis – Movement of cytoplasm MICROTUBULES • Hollow, cylindrical structures • Helps to give cell its shape • Made of tubulin • Involved in mitosis • More information Cytoplasm • Watery material lying within the cell between the cell membrane and the nucleus • Formally called the protoplasm by Purkinje • Contains all the other organelles RIBOSOMES • Very small • “mini factories” of the cell • Responsible for protein synthesis with the help of RNA • Examples: John Morrell, Gateway ENDOPLASMIC RETICULUM (ER) • Fluid filled canals • Continuous paths for transport of materials • Divides the cell into compartments ER continued • Acts as a “street system” in a city or conveyer at a factory • Rough ER = surface lined with ribosomes • Smooth ER = no ribosomes GOLGI BODIES • Packaging, storage and processing of proteins • “ Post Office ” of the cell • Protein arrives from the ER to be packaged in vesicles. ER, Ribosome, & Golgi LYSOSOMES • Many strong digestive enzymes • Produced by Golgi Bodies • Involved in digestion of food in the cell • Helps break down worn out organelles and wastes • “ Garbage Truck ” • Recycles cell materials VACUOLES • Found mainly in plants but a few are found in animal cells • Many different types • Examples: Food and contractile • Act as a storage unit Contractile vacuoles • Location in plant cells where excess water collects Chloroplasts • A special type of chromoplast that contains chlorophyll • Most important • Contains grana and stroma • Contain their own DNA • Site of photosynthesis Chloroplast Structure MITOCHONDRIA • Release energy used by the cell • “power plant” • Double membrane for extra surface area • Responsible for cellular respiration – Process by which energy is released using oxygen Mitochondria structure Mitochondria (powerhouse) • Act similar to electric power plant • Upto 300 to 800 per cell • What advantage is their to having its own DNA? • Can replicate itself Organelle DNA • The only two organelles that contain their own DNA are mitochondria and chloroplasts • In animals, all of an organisms organelle DNA is maternal in origin. • Why? CELL MEMBRANE • Controls what materials move in and out • Helps to maintain homeostasis • Similar to the “city limits” • Made up of three substances : – Lipids, proteins, and carbohydrates Fluid-Mosaic Model Protein functions 1) Transport proteins = control movement of materials. 2) Receptors = act to signal cell when to begin or stop metabolizing. 3) Enzymes = start chemical rxns. 4) Binding site for internal structures. Selectively permeable Some substances pass through while others may not. Regulates chemical composition Maintains homeostasis Diffusion • Movement of molecules from a region of high concentration to a region of low concentration Osmosis • Diffusion of WATER across a selectively permeable membrane from a region of high water concentration to a region of low water concentration. • Osmotic pressure = – Increased pressure resulting from osmosis Isotonic solution • Same concentration of dissolved substances in solution as there is in the cell • Same water concentrations • Net result – No net gain or loss of water Hypotonic solution • Lower concentration of dissolved substances in solution than in the cell • More water outside the cell than inside the cell • Net result : Hypertonic pressure • A high concentration of dissolved substances outside the cell • More water in the cell than outside the cell • Net result : Facilitated diffusion vs Active transport • Facilitated diffusion • No energy needed • Concentration gradient determines movement • Uses protein channels • ACTIVE • Usually works against the conc. Gradient • Often a transport protein helps the movement (ATP) Sodium-potassium pump Endocytosis • Transport of material into the cell by means of a vesicle 1. Pinocytosis = small amounts of liquid engulfed 2. Phagocytosis = small amounts of solid ingested Exocytosis • Transport of material out of the cell by means of a vesicle • Exocytosis movie Cellular organization • Simplest form of life: unicellular Ex. bacteria, protists, algae • Multicellular: – The simplest form is that of a colony – Little if any cellular specialization – Example: Volvox (algae) Organization CELLS TISSUES ORGAN SYSTEM ORGANISM ORGANS Tissues: • A group of cells which are structurally similar and perform the same function. 1. Epithelial Tissue • Tissue that covers surfaces inside and outside the body • Example: skin • Sheets of closely packed cells 2. Connective Tissue • Supports and binds tissues and organs together • Widely separated cells • EX. bone, blood 3. Nervous Tissue • Specialized for electrical impulse transport • Ex. brain, spinal cords, nerves 4. Muscle Tissue • Specialized for contraction • Lots of mitochondria Organs • Group of tissues that work together to perform a specific function • Ex. heart, stomach, flower Organ system • Group of organs that perform a specific task • Ex. digestive, skeletal, circulatory Assignment • Pages 197-198 – 1-10,11,12,15,17,18,22,26,27 Page 199 1-11