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Cells Types of Cells prokaryotes eukaryotes organelles also fungus & protist cells no organelles plant cells bacteria cells animal cells Cell size comparison Animal cell Bacterial cell • Most bacteria • 1-10 microns • Eukaryotic cells • 10-100 microns micron = micrometer = 1/1,000,000 meter diameter of human hair = ~20 microns Why study cells? • Cells Tissues Organs Bodies • Bodies are made of cells • Cells do all the work for life The work for life • STERNGRR • Synthesis: build molecules (carbs, lipids, proteins, nucleic acids) • Transport: move materials in/out & within the cell • Excretion: remove wastes • Respiration: gas exchange; make energy • Nutrition: take in & digest food • Grow & repair • Regulation: control internal conditions (homeostasis) • Reproduction: make more cells • Respond to external environment ATP The main jobs of cells • Cells have 3 main jobs: • Make energy ATP • Need energy for all activities • Need to clean up waste produced by energy production • Make proteins • Proteins do all the work in the cell, so we need lots of them Our organelles do of these jobs?! • All Make more cells AWESOME!! • For growth • For repair (replace damaged or diseased cells) Parts of the Cell Theory • All living things are made of one or more cells • Cells are the basic unit of structure & function in organisms • Cells come only from the reproduction of preexisting cells Cell Scientists • Robert Hooke • looked at cork under a microscope • 1st to use term “cell” Cell Scientists • Anton van Leeuwenhoek • looked at pond water • 1st to see living cells • called them “animalcules” Cell Scientists • Schleiden, Schwann, & Virchow • came up with the cell theory Cell Scientists • Schleiden • 1838 • claimed plants are made of “independent, separate beings” called cells Cell Scientists • Schwann • 1839 • claimed animals are also made of cells Cell Scientists • Virchow • 1855 • stated that living cells must come from other living cells Cell Scientists • Louis Pasteur • 1860’s • disproved spontaneous generation The Cell Theory Prokaryotic vs Eukaryotic Cells Prokaryotic Cells • • • • • • • • • Appeared 3.5 billion years ago Primitive, simple Small in size (less than 10 µm) No membrane-bound organelles DNA in cytosol (nucleoid region) Single, circular chromosome “Naked” DNA Smaller ribosomes (70S) BACTERIA Eukaryotic Cells • • • • • • • • Appeared 1.5 billion years ago Complex More than 10 µm in size Contain membranebound organelles Larger ribosomes (80S) Paired, linear chromosomes DNA wrapped around histones (proteins) NUCLEUS • Let’s draw a prokaryotic cell and label it …. Prokaryotic reproduction • Asexual = binary fission • Produces two DNA Copies identical daughter cells Cytokinesis Clones! Prokaryotic reproduction • Sexual = conjugation • Uses conjugation pili to exchange plasmids Parts of a Eukaryotic Cell Plasma Membrane • Also called the Cell Membrane • Separates cell from its environment Plasma Membrane • Semipermeable • Allows only certain molecules to enter or exit Plasma Membrane • Phospholipid Bilayer • Embedded with proteins • Cholesterol is embedded in bilayer to help membrane fluidity Nucleus • “Boss” or “Brain” of the cell • Controls cellular activities • Contains DNA (chromosomes) Nucleus • Nuclear Membrane • Surrounds nucleus • Double membrane • Contains nuclear pores (holes) Nucleus • Nucleolus • Produces ribosomes • Ribosomes leave through nuclear pores Cytoplasm • Cytosol • Fluid portion • Organelles • Membrane-bound compartments that carry out specific functions Mitochondria • Breaks down glucose to CREATE ENERGY (ATP) • Active cells (muscle) -> hundreds of mitochondria • Inactive cells (fat) -> few mitochondria • Have own DNA & ribosomes • Have a double membrane Ribosomes large subunit small subunit ribosome • Create proteins • Composed of 2 interlocking subunits • Some float free in cytosol • Some attach to the ER Endoplasmic Reticulum (ER) • Intracellular highway • 2 Types • Rough ER • Smooth ER Endoplasmic Reticulum (ER) • Rough ER • Covered in ribosomes • Transport and develop proteins • may be used in membranes, enzymes, and cell communication Endoplasmic Reticulum (ER) cisternal space polypeptide signal sequence ribosome ribosome mRNA Synthesizing proteins membrane of endoplasmic reticulum cytoplasm Endoplasmic Reticulum (ER) • Smooth ER • Lacks ribosomes • Produces lipids, estrogen, & testosterone • Helps detoxify drugs & poisons • Increased use = increased smooth ER • Possibly linked to increased tolerance Endoplasmic Reticulum (ER) Golgi Apparatus • Transport (FedEx/UPS of the cell) • Collects, packages, modifies, and distributes materials made in the cell • Prevalent in cells that secrete substances nucleus Vesicles • Lysosomes lysosomes • Contain digestive enzymes • Digest organic molecules, worn organelles, or dying cells Vesicle transport protein vesicle budding from rough ER ribosome migrating transport vesicle fusion of vesicle with Golgi apparatus Vacuoles – Plant cells • Central vacuole • Large, fluid-filled organelle • Stores water, ions, enzymes & waste • Can be up to 90% of cell’s volume • Why so big in plants? Vacuoles – Animal cells • Food vacuoles • Store and process food • Contractile vacuoles • Removes excess water from cell • Prevents cell from exploding Working together … ER vesicle Golgi complex vesicle vesicle vacuole Centrosome • Centrosome • Assembles microtubules • May contain centrioles • Used during cell division Cilia/Flagella • Cilia • Hair-like • Short & numerous • Flagella • Tail-like • Long & less numerous Plant Cell versus Animal Cell Animal Cells Only! • Cytoskeleton • Network of microtubules & filaments • Gives the cell shape • Holds organelles in place Plant Cells Only! • Cell Wall • Rigid layer surrounding plasma membrane • Made of cellulose • Pores allow water, ions, & other molecules to pass • Bacteria (peptidoglycan), some protists & fungi (chitin) also have cell walls Plant Cells Only! • Chloroplast • Contain chlorophyll • Site of photosynthesis • Energy (sunlight) food • Contain own DNA & ribosomes • Have a double membrane Any Questions??