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Transcript
Cell Structure and Function The Cell Theory • All living things are made of one or • • more cells All cells come from pre-existing cells Cells are the basic unit for structure and function of all organisms Cell structure • All cells are surrounded by a plasma (cell) • • membrane Cells contain organelles - small structures inside cells that perform various jobs All cells can be divided into two main categories: Prokaryotic vs. Eukaryotic Cells Prokaryotic Eukaryotic - no nucleus - Very small (1-10 - have a nucleus - Larger 10-100um um) - Have very few organelles (some larger) - Have many organelles Eukaryotic Cells • Plant and animal cells are eukaryotic as well fungi and protists (amoeba, paramecium, etc) • Plant and animal cells have important differences (see diagrams) Eukaryotic Cellular Organization • Single celled organisms (unicellular) • Multiple celled organisms (multicellular) - in multicellular organisms, cells become specialized (do a particular job) Plasma (cell) membrane • Consists of a double layer of lipids • The outside and inside of the membrane is hydrophilic (“water-loving”) • The interior of the membrane is hydrophobic (“water-fearing”) • Substances must cross the membrane to enter and exit the cell Types of Membrane Transport Passive Transport (requires NO energy) • Moves substances from a high to a low concentration • Diffusion & osmosis, facilitated diffusion Active Transport (requires energy) • Substances move from a low to a high concentration • Endocytosis & exocytosis Concentration gradient • Passive transport • moves substances WITH (or DOWN) their concentration gradient Active Transport moves substances AGAINST their concentration gradients PASSIVE TRANSPORT a dna ™emiTkciuQ rosserpmoced )desserpmocnU( F FIT .erutcip siht ees ot dedeen era HIGH LOW ACTIVE TRANSPORT Diffusion • Movement of a substance from a high concentration to a low concentration QuickTi me™ a nd a TIFF (Uncompre ssed ) decomp resso r are need ed to se e th is p icture. Osmosis • Movement of water from a high water concentration to a low water concentration QuickTime™ and a TIFF (Uncomp resse d) de com press or are nee ded to s ee this picture. Osmosis in Different Cellular Environments • Hypotonic - solution with • • a lower solute concentration than the cytoplasm of the cell Hypertonic - solution with a higher solute concentration than the cytoplasm of the cell Isotonic - has same solute concentration as the cytoplasm of the cell QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. • Turgor pressure - pressure (from water) pushing against the cell wall of a plant (makes plant cells firm) • Plasmolysis - shrinking of the cytoplasm of a cell caused by the loss of water (causes plants to wilt) Facilitated Diffusion • Diffusion using • membrane protein channels Some substance must use protein channels since they cannot pass through the lipid layer of the membrane QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Active Transport • Requires the input of • energy to move a substance against its concentration gradient (low to high) Energy is used in the form of ATP (energy molecule produced in mitochondria) QuickTime™ and a TIFF (Uncomp resse d) d eco mpres sor are nee ded to s ee this picture . Types of Active Transport: Endocytosis, Exocytosis and Ion Pumps • Endocytosis - cell takes in • • substances too large to pass through the membrane Exocytosis - cell gets rid of large substances Ion pumps - pump ions against their concentration gradient See endocytosis and exocytosis in action