Transcript Lecture 6
Cell Theory Robert Hooke: saw “little rooms” when examining cork with his self-made microscope. - cells Four main principles: 1. all organisms consist of one or more cells 2. cells are the smallest living things 3. today’s life is a continuous line of descent 4. all cells come from cells Cells are limited in size - surface-to-volume ratio important - surface area A cell is a sack of rich broth containing salts, minerals, and organic compounds. 1. Is filled with cytoplasm 2. Contains many substructures A cell is a sack of rich broth containing salts, minerals, and organic compounds 1. Is filled with cytoplasm 2. Contains many substructures Cells are active and vital Main components of the cell 1. Cell membrane (plasma membrane) Regulates movement of substances into and out of cell Some molecules may pass freely across Some molecules may not pass freely across Selective permeability 2. Cytoplasm Colorless liquid that fills cell Organelles found within - each with a specific function Organelles surrounded by membranes • Composition Cell Membrane a. Lipids, proteins, carbohydrates b. Primary component = phospholipids c. Embedded proteins 2. lipid bilayer a. phospholipids b. nonpolar fatty acids turn away from H2O c. polar heads turn toward H2O 3. Embedded membrane proteins a. most are transmembrane 3. Embedded membrane proteins a. most are transmembrane b. selective transport c. some are enzymes d. some are receptors for signal transduction i.e., for neurotransmitters and hormones • Fluid Mosaic Model 1. Plasma membrane is not a “solid” structure. 2. Individual lipid and protein molecules are not covalently bonded together. 3. The lipid bilayer acts like a 2-D fluid. 4. Some of the proteins are “floating” and can move about. Cell Types Prokaryotes (bacteria) 1. simple 2. have no organelles 3. have some substructures Cell Types Eukaryotes 1. have membrane-bound organelles 2. DNA is found inside a nucleus 3. are larger Cytoskeleton made up of protein fibers Functions of Cytoskeleton a. Support the cell like a “skeleton” b. Maintains cell shape c. Movement d. Connects organelles Microtubules 1. Hollow cylindrical structures - made up of individual subunits (tubulins) Microtubules 1. Hollow cylindrical structures - tubulins 2. Support “scaffolding” all cells would otherwise form a sphere Microtubules 1. Hollow cylindrical structures - tubulins 2. Support “scaffolding” all cells would otherwise form a sphere 3. Provide the “machinery” for cellular movement - cilia and flagella made of microtubules - also used to move organelles and chromosomes within cells Microfilaments 1. Solid rods of protein - actin is the primary one 2. Responsible for contraction in muscle cells 3. Found in virtually all cells • Cilia Motility hair-like projections on surface of cell used by some single-celled organisms to “swim” found on cells lining certain body passages trachea oviduct Motility • Flagellum long whip-like “tail” propulsion through liquid Motility • Cilia hair-like projections on apical surface of cell found on cells lining certain passages trachea oviduct • Flagellum long whip-like “tail” sperm propulsion • Similar composition 9 + 2 arrangement of microtubules axoneme