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The Cell Theory

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The Cell Theory 11/15/2015 The History of Cells & the Discovery of Cells Cell Theory 1665- English Scientist, Robert Hooke, discovered cells while looking at a thin slice of cork. He described the cells as tiny boxes or a honeycomb He thought that cells only existed in plants and fungi Anton van Leuwenhoek 150-200 Year Gap??? 1673- Used a handmade microscope to observe Between the Hooke/Leuwenhoek discoveries pond scum & discovered single-celled organisms and the mid 19th century, very few cell theory He called them “animalcules” advancements were made. This is probably due to the widely accepted, traditional belief in Spontaneous Generation. Examples: He also observed blood cells from fish, birds, -Mice from dirty clothes/corn husks frogs, dogs, and humans -Maggots from rotting meat Therefore, it was known that cells are found in animals as well as plants 19th Century Advancement Development of Cell Theory Much doubt existed around Spontaneous Generation 1838- English Botanist, Matthias Schleiden, Conclusively disproved by Louis Pasteur concluded that all plant parts are made of cells Pasteur: Ummm, I 1839- German physiologist, Theodor Schwann, don’t think so!!! who was a close friend of Schleiden, stated that ? all animal tissues are composed of cells. = + 1 11/15/2015 Development of Cell Theory 3 Basic Components of the Cell Theory 1858- Rudolf Virchow, Russian physician, after extensive study of cellular pathology, 1. All organisms are composed of one or more cells. concluded that cells must arise from (Schleiden & Schwann)(1838-39) preexisting cells. 2. The cell is the basic unit of life in all living things. (Schleiden & Schwann)(1838-39) 3. All cells are produced by the division of preexisting cells. (Virchow)(1858) Theory Modern Cell Theory Modern Cell Theory consists of the 3 basic components A set of statements or principles of cell theory, plus 4 additional statements: devised to explain a group of 4. The cell pass information from cell to cell during cell division using DNA. facts or phenomena, especially 5. All cells have basically the same chemical one that has been repeatedly composition and metabolic activities. tested or is widely accepted and 6. All cells have basically the same chemical & can be used to make predictions physiological functions.(movement, digestion, etc) 7. Cell activity depends on the activities of structures about natural phenomena. within the cell. (organelles, nucleus, plasma membrane) Characteristics of Cells How Has The Cell Theory Been Used? All Cells have common structures The previously discovered truths Cell Membrane about cells listed in the Cell Theory are the basis for things such as: Ribosomes Disease/Health/Medical Research Cytoplasm and Cures(AIDS, Cancer, Vaccines, Cells contain DNA Cloning, Stem Cell Research, etc.) Found in the nucleus Cells are independent units of life 2 11/15/2015 Prokaryotic cells Characteristics of Prokaryotes Components Cytosol does not have a nucleus Ribosomes single celled organisms Nucleoid region Circular DNA have few organelles Plasmid perform few functions Cell Membrane Eat Cell Wall Capsule Respire (or slime layer) Reproduce Pili Flagellum smaller than other cells Bacteria are the only known prokaryotes Characteristics of Viruses Bacteriophage Virus “bacteria eater” • Viruses are not living because they: are not made of cells need a host cell to reproduce • A virus is very small compared to a cell • Like cells, viruses contain nucleic acids 3 11/15/2015 Components Characteristics of Eukaryotes Cytosol Eukaryotic cells Nucleus Mitochondria has a nucleus Chloroplast Ribosomes can be single or multicellular Rough ER have many organelles, Smooth ER Golgi body performing complex functions Vacuoles specialized to perform Lysosomes specific functions Cytoskeleton Centriole larger than prokaryotic cells Cilium and Flagellum Animals, plants, fungi and Cell membrane protists are made of Cell Wall eukaryotic cells Animal and Plant Cells Summary of Differences Both Have: Prokaryotic Cells Eukaryotic cells small cells (< 5 mm) larger cells (> 10 mm) A nucleus always unicellular often multicellular no nucleus or any membrane-bound always have nucleus and other Ribosomes that make protein organelles membrane-bound organelles DNA is circular, without proteins DNA is linear and associated with Rough and smooth endoplasmic proteins to form chromatin reticulum ribosomes are small (70S) ribosomes are large (80S) Golgi bodies no cytoskeleton always has a cytoskeleton Mitochondria cell division is by binary fission cell division is by mitosis or meiosis Cytoplasm reproduction is always asexual reproduction is asexual or sexual Vacuoles that store food, water and waste products. Animal Cells Animal cells cont. Do not have a cell wall Can not make their own food Do not have a large vacuole Have many lysosomes Do not have chloroplasts Are more round shaped Have centrioles Use mitochondria to release energy Have many Golgi bodies Have more extensive cytoskeleton than plant cells 4 11/15/2015 Figure 3.2 Structure of the generalized cell. Chromatin Nuclear envelope Nucleolus Nucleus Animal Cell Diversity Plasma Smooth endoplasmic membrane reticulum Cytosol Mitochon- drion Lysosome Centrioles Rough Centro- endoplasmic some reticulum matrix Ribosomes Golgi apparatus Secretion being released from cell by exocytosis Cytoskeletal elements • Microtubule • Intermediate filaments Peroxisome © 2013 Pearson Education, Inc. Figure 7-5 Plant and Animal Cells Eukaryotic Cell Organelles and Section 7-2 Animal Cell Function Cytoplasm Nucleolus Ribosomes 1. Nucleus Nucleus Cell Membrane Nickname: “The Control Center” Function: holds the DNA Smooth Endoplasmic Rough Endoplasmic Reticulum Parts: Reticulum 1. Nucleolus: dark spot in the middle of the nucleus that helps make ribosomes Golgi Bodies Go to Section: Nucleus – largest organelle; control center of the cell; consists of: Nuclear envelope – double membrane structure containing pores Nucleoli – synthesize ribosomes Chromatin – threadlike material composed of DNA (genes) & proteins Note: during cell division, chromatin condenses to form chromosomes Figure 3.28a 5 11/15/2015 Cytoplasm Consists of: Cytosol – liquid portion Mitochondria Organelles – specialized cellular compartments Nickname: “The Powerhouse” Function: Energy formation Inclusions – chemical substances Breaks down food to make ATP Glycogen (muscle & liver cells) – ATP: is the major fuel for all cell activities that Lipid droplets (fat cells) require energy Melanin granules (skin & hair cells) Mitochondria – double membrane structures; site of cellular respiration (ATP synthesis) Contain their own DNA & RNA Able to replicate themselves Ribosomes – dense particles of rRNA and protein Free ribosomes – synthesize proteins that function within the cell Ribosomes Attached ribosomes – synthesize proteins Function: makes proteins incorporated into cell membranes or Found in all cells, prokaryotic and exported outside the cell eukaryotic 6 11/15/2015 Cytoskeleton – network of rods that support Microfilaments – thin filaments composed of the cell actin Microtubules – thick rods composed of involved in muscle contraction tubulin form cleavage furrow during cell division form cilia, flagella & centrioles Intermediate filaments – tough protein fibers attached to desmosomes Cellular extensions Centrioles – paired cylindrical bodies Microvilli: fingerlike composed of microtubules projections of the plasma Organize spindle apparatus (cell division) membrane; increase surface area for absorption Cilia: short hair-like projections; propel substances over surface of cell Flagella: long hair-like projections; propel the cell Endoplasmic Reticulum Endoplasmic Reticulum (ER) 2 Types: Nickname: “Roads” 1. Rough ER: Function: The internal delivery system of – Rough appearance because it has the cell ribosomes – Function: helps make proteins, that’s why it has ribosomes 2. Smooth ER: – NO ribosomes – Function: makes fats or lipids 7 11/15/2015 . Endoplasmic reticulum (ER) – extensive membrane system Functions 1. Synthesis of proteins, carbohydrates, and lipids 2. Storage of synthesized molecules and materials 3. Transport of materials within the ER 4. Detoxification of drugs or toxins Rough ER – studded with ribosomes; abundant in secretory cells Smooth ER – free of ribosomes Synthesizes lipids and steroids Detoxifies drugs/poisons (liver cells) Stores calcium ions (muscle cells) Figure 3.18 Golgi Apparutus AKA Golgi Body or Golgi complex Nickname: The shippers Function: packages, modifies, and transports materials to different location inside/outside of the cell Appearance: stack of pancakes Figure 3.19 Golgi apparatus – stack of flattened membranous sacs Packages proteins for secretion from the cell (exocytosis) Packages proteins for incorporation into plasma membrane Forms lysosomes Figure 3.21 8 11/15/2015 Lysosomes – membranous sacs of hydrolytic enzymes; sites of intracellular digestion Lysosomes: circular (but bigger than Primary lysosome ribosomes) Formed by Golgi apparatus and inactive enzymes Secondary lysosome Nickname: “Clean-up Crews” Lysosome fused with damaged organelle Function: to break down food into Digestive enzymes activated particles the rest of the cell can use and Toxic chemicals isolated to destroy old cells Peroxisomes – membranous sacs of oxidase & Plant Cells catalase enzymes; detoxify alcohol & neutralize dangerous free radicals Have
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