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Transcript
Chapter 4 DISCOVERING THE CELL Discovering the Cell • Robert Hooke – Simplistic microscope to examine cork – Referred to compartments as ‘cellulae’ • Origin for today’s term cell • Antoni Van Leeuwenhoek – Invented many simplistic microscopes – 1st to observe and describe bacteria • Termed ‘animalcules’ • Contemporaries in the late 1600’s Cell Theory • All living things are composed of cells – Schleiden and Schwann – 1 to many billions with different functions • Smallest unit to demonstrate properties of life • New cells are only formed from existing cells – Virchow – Mitosis and meiosis Compound Light Microscope • Visible light is refracted (bent) through glass lenses • Apparent size seen is magnification • Clarity to discern 2 points as distinct is resolution – HD TV’s, DVD players, and Blue-Ray players Electron Microscope (EM) Scanning (SEM) Transmission (TEM) • Details of cell surfaces, 3D image • Details of internal cell structures • Uses a beam of electrons = higher resolution • Can’t be used on living cells Limits on Cell Size • Communication time b/w inside and outside • Interaction of with environment – Ratio of surface area to volume • Larger volume needs more nutrients = more wastes • More surface area speeds mov’t of ‘stuff’ – Volume increases faster than surface area with growth • Cell so big transport can’t keep up • Effects shapes and body plans too Cellular Classification • Prokaryotes – – – – – NO nucleus (nucleoid region) NO membrane bound organelles Single, circular DNA Smaller, less complex E.g. bacteria and archaea • Eukaryotes – Nucleus – Membrane bound organelles – DNA arranged on multiple chromosomes – Larger, more complex – E.g. protists, fungi, plants, and animals The Basic Cell • Plasma membrane – Phospholipid bilayer – Regulates mov’t in and out • Cytoplasm – Fills cell – Contains organelles and surrounding substances • DNA – Genetic material – Location varies in cell types • Ribosomes – Synthesize proteins – Composition varies in cell types Prokaryotic Cells • Nucleoid region • Chromosome/DNA (see previous) • Cell membrane • Cell wall (peptidoglycan) • Capsule (glycocalyx) • Cytoplasm • Ribosomes (antibiotic functions • Pili • Flagellum/cilia Eukaryotic Cells • Most living organisms – – – – Protists Fungi Plants Animals • Organelles allow compartmentalizing – Different areas carrying on reactions independently of rest of cell • Endomembrane system connects – Nuclear membrane rough ER smooth ER golgi apparatus lysosomes/vacuoles plasma membrane Nucleus • Control center • Nucleolus – Constructs ribosomes • Chromatin – All DNA in cell – Organized into chromosomes – 6 Feet of DNA in one nucleus!!! • Nuclear envelope/membrane – Regulates transport of molecules – Receptors for signaling – Nuclear pores • Allow communication with cytoplasm Endoplasmic Reticulum (ER) • Smooth ER – No ribosomes – Lipid synthesis – Carbohydrate synthesis • Rough ER – Ribosomes attached • Protein and rRNA • Free or attached – Synthesize proteins Golgi Apparatus (Body) • Package and process proteins & lipids – “Warehouse & finishing factory” • Polarity – Receives vesicles from ER – Produces finished vesicle products Cellular Production • Vesicles are sacs containing enzymes – Lysosomes • Intracellular digestion • Destroy bacteria in white blood cells • Breaks down damaged organelles – Peroxisomes • Break down fatty acids & proteins • Detoxify alcohol & other toxic substances • Vacuoles are large storage vesicles – Varies between eukaryotic cells • Food vacuoles • Contractile vacuoles protists • Central vacuoles plants Cellular Energy • Mitochondria eukaryotic cells – Site of cellular respiration • Forms ATP (energy) from carbohydrates – Similar to bacteria have their own DNA & ribosomes – Double membrane, matrix, cristae • Chloroplast plants and algae – Site of photosynthesis • Forms sugars from sunlight – Double membrane, thylakoids, grana, stroma • Theorized as both results of endosymbiosis Cytoskeleton • Protein fibers that extend throughout the cytoplasm • Microfilaments – Supports shape and allows change • Intermediate filaments – Reinforce shape and anchors organelles • Microtubules – Produce movement • Cilia, flagella, and pseudopodia – Assembled by centrioles Eukaryotic Cell Types Animal Cells Plant Cells