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UT Arlington BIOL 2457 - Chapter 3: The Cellular Level of Organization

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BIOL 2457 1st Edition Lecture 6Outline of Last Lecture I. Acids, Bases, and SaltsOutline of Current LectureI. The cellular level of organization CELL THEORYI. The three tenets to cell theory are: II. All organisms are composed of one or more cells.III. The cell is the most basic unit of structure, function, and organization in all organisms.IV. All cells arise from pre-existing, living cells.V. BIG IDEAS IN CELL BIOLOGYVI. Genetic information stored in one-dimensional chemical sequences in DNA (occasionally RNA) is duplicated and passed on to daughter cells.VII. One-dimensional chemical sequences stored in DNA code for both the linear sequences and three-dimensional structures of RNAs and proteins and ultimately the architecture of cells and tissues.VIII. Macromolecular structures assemble from subunits.IX. Membranes separate cells from their external environment, form biochemically distinct compartments in eukaryotic cells, and grow by expansion of preexisting membranes.X. Signal–receptor interactions target cellular constituents to their correct locations.XI. Many cellular constituents move by diffusion, but energy-consuming pumps and motors move some constituents and whole cells.XII. Receptors and signaling mechanisms allow cells to adapt to environmental conditions.XIII. Molecular feedback mechanisms control molecular composition, growth, anddifferentiation.XIV. A Generalized Cell1. Plasma membrane- forms the cell’s outer boundary2. - separates the cell’s internal environment from the outside environment- is a selective barrier- plays a role in cellular communicationXV. A Generalized CellXVI. 2. Cytoplasm- all the cellular contents between the plasmaXVII. membrane and the nucleus - cytosol - the fluid portion, mostly water- organelles - subcellular structures havingXVIII. characteristic shapes and specific functions XIX. A Generalized CellXX. 3. Nucleus- large organelle that contains DNA- contains chromosomes, each of which XXI. consists of a single molecule of DNA and XXII. associated proteins- a chromosome contains thousands of XXIII. hereditary units called genesXXIV. Plasma MembraneXXV. Flexible yet sturdy barrierXXVI. The fluid mosaic model - the arrangement of molecules within the membrane resembles a sea of lipids containing many types of proteinsXXVII. The lipids act as a barrier to certain substancesXXVIII. The proteins act as “gatekeepers” to certain molecules and ionsXXIX. Structure of a MembraneXXX. Consists of a lipid bilayer - made up of phospholipids, cholesterol and glycolipidsXXXI. Integral proteins - extend into or through the lipid bilayerXXXII. Transmembrane proteins - most integral proteins, span the entire lipid bilayerXXXIII. Peripheral proteins - attached to the inner or outer surface of the membrane, do not extend through itXXXIV. Structure of a MembraneXXXV. Glycoproteins - membrane proteins with a carbohydrate group attached thatprotrudes into the extracellular fluidXXXVI. Glycocalyx - the “sugary coating” surrounding the membrane and made up ofthe carbohydrate portions of the glycolipids and glycoproteinsXXXVII. Functions of Membrane ProteinsXXXVIII. Some integral proteins are ion channelsXXXIX. Transporters - selectively move substances through the membraneXL. Receptors - for cellular recognition; a ligand is a molecule that binds with a receptorXLI. Enzymes - catalyze chemical reactionsXLII. Others act as cell-identity markersXLIII. Membrane PermeabilityXLIV. The cell is either permeable or impermeable to certain substancesXLV. The lipid bilayer is permeable to oxygen, carbon dioxide, water and steroids, but impermeable to glucoseXLVI. Transmembrane proteins act as channels and transporters to assist the entrance of certain substances, for example, glucose and ionsXLVII. Passive vs. Active ProcessesXLVIII. Passive processes - substances move across cell membranes without the input of any energy; use the kinetic energy of individual molecules or ionsXLIX. Active processes - a cell uses energy, primarily from the breakdown of ATP, to move a substance across the membrane, i.e., against a concentration gradientL. DiffusionLI. Steepness of LII. concentration gradientLIII. TemperatureLIV. Mass of diffusing substanceLV. Surface areaLVI. Diffusion distanceLVII. OsmosisLVIII. Net movement of water through a selectively permeable membrane from an area of high concentration of water (lower concentration of solutes) to one of lower concentration of waterLIX. Water can pass through plasma membrane in 2 ways:1. through lipid bilayer by simple diffusion2. through aquaporins, integral membrane proteinsLX. Active TransportLXI. Solutes are transported across plasma membranes with the use of energy, from an area of lower concentration to an area of higher concentration LXII. Example: Sodium-potassium pumpLXIII. Secondary Active Transport MechanismsLXIV. Antiporters carry two substances across the membrane in opposite directionsLXV. Symporters carry two substances across the membrane in the same directionLXVI. Transport in VesiclesLXVII. Vesicle - a small spherical sac formed by budding off from a membrane LXVIII. Endocytosis - materials move into a cell in a vesicle formed from the plasma membrane LXIX. three types: receptor-mediated endocytosis - phagocytosis1. bulk-phase endocytosis (pinocytosis)LXX. Exocytosis - vesicles fuse with the plasma membrane, releasing their contents into the extracellular fluid LXXI. Transcytosis - a combination of endocytosis and


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UT Arlington BIOL 2457 - Chapter 3: The Cellular Level of Organization

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