BSC2010 EXAM 2 Chapters 6 10 Chapter 6 Microscopes given the ability to visualize cells progresses have lead to ability to view smaller parts of the cell Electron microscope used to study sub cellular structures and there are two types 1 scanning electron microscope provide images that look 3D by focusing a beam of electrons ONTO to specimen transmission electron microscope focus a of electrons THROUGH specimen 2 Cell Fractionation takes cells apart and separates the major organelles from one another enables scientists to determine the function of organelles structures of cell Prokaryotic cells bacteria and archaea no nucleas DNA in unbound region called nucleoid no membrane bound organelles cytoplasm is bound by plasma membrane Eukaryotic cells Protists fungi animals and plants DNA is in nucleus which is bounded by membranous envelope Has membrane bounded organelles These cells are much larger than Prokaryotic cells Cytoplasm in region b t plasma membrane and nucleus Basic feature for all cells plasma membrane cytosol cytoplasm chromosomes carry genes Ribosomes makes protein Cytoskeleton network of fibers that organizes structures and activities in the cell helps the cell keep its shape plays a part in movement in cells with the interaction of motor proteins composed of three parts microtubules microfilaments intermediate filaments these structures include cell walls of plants extracellular matrix ECM of animal cells and intercellular junctions Cell wall distinguishes plant cell from animal cell protects plant cells maintain its shape and prevents excessive uptake of water made up of cellulose fibers embedded in other polysaccharides and proteins Plasmodesmata are channels between the adjacent plant cells ECM instead of a cell wall animal cells are covered with this made up of glycoproteins and also bind to receptor proteins called integrins Intercellular junctions facilitate direct contact of cells in tissues that allow them to communicate adhere and interact Plasmodesmata are plants intercellular junctions Tight junctions Desmosomes and Gap junctions are part of the animal cell Plasmodesmata connects the cytoplasm of cells which allows water and small solutes can pass from cell to cell Tight Junctions cells are pressed together preventing leakage of extracellular fluid Desmosomes anchoring junctions fasten cells together into strong sheets which involves the cytoskeleton Gap Junctions communication junctions provide cytoplasmic channels b t adjacent cells Cellular Membranes Chapter 7 Are a mosaic of lips and proteins Phospholipids in the membrane can move within the bilayer most lipids and proteins Membranes must be fluid to work properly Membranes rich in unsaturated fatty acids are more fluid than those rich in saturated Lipid steroid cholesterol has opposite effects on membrane when it comes to drift laterally temperature At cool temperature this lipid maintains fluidity Membrane Protein determine most of the membranes functions Membrane carbohydrates can be covalently bonded to lips forming glycolipids and proteins forming glycoproteins Vocabulary Selective permeability a property of biological membranes that allows them to regulate the passage of substances across them Fluid mosaic model the currently accepted model for cell membrane structure which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids Diffusion the spontaneous movement of a substance down its concentration or electrochemical gradient from a region where it is more concentrated to a region where it is less concentrated Concentration gradient a region along which the density of a chemical substance increases or decreases Osmosis the diffusion of free water across a selectively permeable membrane Facilitated diffusion the passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific trans membrane transport protein requiring no energy expenditure Ion channel a trans membrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient o particular stimulus Gated channel a trans membrane protein channel that opens or closes in response to a Active transport the movement of a substance across a cell membrane against its concentration or electrochemical gradient mediated by specific transport proteins and requiring an expenditure of energy Sodium potassium pump a transport protein in the plasma membrane of animal cells that actively transport sodium out of the cell and potassium into the cell Membrane potential the difference in electrical charge voltage across a cells plasma membrane due to the differential distribution of ions Membrane potential affects the activity of excitable cells and the trans membrane movement of all charged substances Electrochemical gradient the diffusion gradient of an ion which is affected by both the concentration difference of an ion across a membrane a chemical force and the ion s tendency to move relative to the membrane potential an electrical force Proton pump an active transport protein in a cell membrane that uses ATP to transport hydrogen ions out of a cell against their concentration gradient generating a membrane potential in the process Co transport the coupling of the downhill diffusion of one substance to the uphill transport of another against its own concentration gradient Exocytosis the cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane Endocytosis cellular uptake of biological molecules and particulate matter via formation of vesicles from the plasma membrane Ligand a molecule that binds specifically to another molecule usually a larger one Phospholipid A lipid made up of glycerol joined to two fatty acids and a phosphate group The hydrocarbon chains of the fatty acids act as nonpolar hydrophobic tails while the rest of the molecule acts as a polar hydrophilic head Phospholipids form bilayers that function as biological membranes Understanding homework 1 What is true of a typical plasma membrane a The two sides of the plasma membrane have different lipid and protein composition i Because the membrane serves different functions on the cytoplasmic and exterior surfaces the structure and composition of the surfaces must be different 2 Singer and Nicolson s fluid mosaic model of the membrane proposed that a Membranes consist
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