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Explore the tools used to observe cells, from light microscopes to electron microscopes. Dive into important concepts like magnification and resolution, and review key elements of cell theory. Learn about the cell membrane, organelles like mitochondria and ribosomes, and nuclear organelles. Discover the roles of centrioles, cytoskeletal elements, and organelles of locomotion. Delve into lysosomes, peroxisomes, and chloroplasts. An informative guide to understanding the intricate world of cells.
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Cell Structure and Function Bio 100 Tri-County Tec. College Pendleton, S. C.
Tools to observe cells-- • Microscopes • light • transmission electron • scanning electron • Each has a unique value to the person studying cells.
The Light Microscope • uses visible light for illumination • magnifies to 1000x (some to 2000x) • good for looking at most cells • living cells can be observed • not good for looking at cell parts
Two important concepts • Magnification defined as “how much larger/bigger the object appears” • Calculated by multiplying the objective by the ocular (40X objective x 10X ocular = 400 X magnification) • Resolution is the ability of a microscope to show two objects as distinct or separate from each other • Catch 22 to be sure • Chalk talk time on resolution
Transmission Electron Micros. • electron beam for illumination • magnifies 100,000x or more • specimen has to be dead and cut into thin sections • good for observing cell parts
Scanning Electron Micros. • electron beam for illumination • can visualize 3D surfaces of whole specimens • specimen must be dead • good for looking a surface architecture of cells
Let’s Review Cell Theory • The cell is the structural and functional unit of life • Whatever “life” is, it begins at the cellular level • All living things are composed of one or more cells • Cells can only come from preexisting cells • Another Catch 22 is spontaneous generation versus biogenesis
The Cell Membrane • Composed of a phospholipid bi-layer with proteins embedded in it • fluid-mosaic model • proteins are randomly distributed in the membrane (mosaic) • proteins are not static in position (fluid) • membrane contains pores
Cell Membrane, ctd. • movement of materials through pores • if smaller than the pores • lipid soluble substances • dissolve in the membrane and move in on the other side • the membrane is selectively permeable • carrier proteins
Organelles of the cell “little organs” that carry out the functions of the cell
Endoplasmic Reticulum • Looks like a maize in the cytoplasm • smooth endoplasmic reticulum (SER) • does not contain ribosomes • rough endoplasmic reticulum (RER) • contains ribosomes • system of channels for internal cellular transport
Golgi Apparatus • Looks like a stack of pancakes • usually near the ER • packages cellular secretions for export from the cell • In some cells, hormones are produced in the ER and the Golgi Apparatus packages these for export.
Ribosomes • Some are located in ER • others float free in cytoplasm • both kinds are the places where proteins are synthesized • composed of RNA (ribosomal-RNA) • protein synthesis takes place in the cytoplasm
Mitochondria • Sites of energy production (ATP synthesis via cellular respiration) • use oxygen to produce ATP • shaped somewhat like a peanut • reactions of energy production take place on numerous membranes that form the inside of the mitochondrion
Centrioles • form the structures that are involved in pulling the chromosomes apart during cell division. • each cell has two • line up at opposite ends of a dividing cell and establish the direction at which division will take place
Nuclear Organelles • located in or associated with the nucleus • nuclear membrane • chromatin • nucleolus • chromosomes • nuclear membrane • controls what enters and exits the nucleus
Nuclear Organelles--2 • Chromatin • stretched out chromosomes • long, thin strands of DNA • Nucleolus • looks like a small nucleus inside the nucleus • synthesizes ribosomes
Nuclear Organelles--3 • chromosomes • before cell division chromatin condenses into chromosomes • composed of DNA • genes are locations on a chromosome that contain directions for making a specific human protein
Cytoskeletal Elements • Microtubules and microfilaments • microtubules • hollow cytoskeletal elements • microfilaments • solid cytoskeletal elements • support the cell from the inside
Organelles of Locomotion • Cilia and flagella • flagella • long, whiplike structures that cause certain cells to move • human sperm cell has a flagellum • cilia • short structures that move materials over the surfaces of certain human tissues
Inclusions • storage areas in the cell • somewhat like closets • surrounded by a membrane • usually spherical in shape like a beach ball • plant cells usually have more inclusions than do animal cells
Lysosomes • Lysosomes • membranous sacs of powerful digestive enzymes • digest worn out cell parts and foreign matter in the cytoplasm • “garbage collectors” of the cell
Peroxisomes • membranous sacs of oxidizing enzymes • detoxify poisons by oxidation • cells produce hydrogen peroxide which is a poison • peroxisomes destroy hydrogen peroxide • “detox” centers
Chloroplasts • Found only in plant cells • location for photosynthesis • production of glucose from carbon dioxide and water • contain chlorophyll (a and b) • Also contain carotenoids and phycobilins
Meanwhile, back at the ranch.. • Plant cells joined together into tissues by cell junctions • Sticky middle lamella cements adjacent cells together • Each plant cell connected to adjoining cells by plasmodesmata • Tiny channels that allow cytoplasm to be continuous between the cells
Extracellular Matrix • Animal cells have elaborate ECM composed mostly of glycoproteins • Tight junctions=continuous belts around cells (membranes of neighboring cells fused at tight junctions) • Anchoring junctions (desmosomes)=rivets fastening cells together into strong sheets • Communicating junctions (gap)=provide cytoplasmic channels between adjacent cells
Eucaryotic vs. Procaryotic One is complex, the other is simple.
Procaryotic Cell • simple, unorganized cell • no membrane-bound organelles • no nuclear membrane • no nucleus • division by binary fission r/t mitosis • small simple ribosomes • examples: bacteria (K. Procaryotae)
Eucaryotic Cell • complex, well organized cell • membrane-bound organelles • nuclear membrane • division involves mitosis • the kind of cell we are composed of and that we have been discussing • members of all other kingdoms
The End The language of the cell is a key to understanding the science of Biology.