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BIOB10H3 (252)
Aarti Ashok (125)
Lecture

Important Terms and Definitions

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Department
Biological Sciences
Course
BIOB10H3
Professor
Aarti Ashok
Semester
Summer

Description
LECTURE#5 x A function of the plasma membrane is that it serves as a scaffold fro biochemical activities eg. signalling proteins send signals to the nucleus x It allows the cell to respond to extracellular signals eg. signals could tell cels to prepare for cell division ; cell surface receptors that bind ligand on the cell exterior can send signals into the cytoplasm of the cell x PM is a lipid bilayer x Hydrophobic interactions of the fatty acid tails of the PM x Protein channels within the bilayer x Short sugar chains on proteins and lipids are called glycoproteins or glycolipids x Membrane lipids are amphipathic, contain both hydrophobic and hydrophilic regions; 3tyes o Phospholipids o Sphingolipids o Cholesterol x Sphingolipids are composed of an amino alcohol with a long hydrocarbon chian called sphingosine and a single fatty acid chain; fatty acid is attached to the amino group of sphingosine; ceramide is the simplest sphingolipid x Glycolipids are formed when a sugar is attached to the terminal alcohol of a sphingosine; certain viruses and txins eg. cholera/influenza toxins bind to cell surface glycoproteins and gain access to cells x 3 types of membrane proteins o Integral membrane proteins: transmembrane proteins (expand bilayer)  Are single or multipass; can pass through membrane once or several times  CFTP is defective in cystic fibrosis patiens (ccystic fibrosis transmembrane proteins) o Peripheral membrane proteins: on cytoplasmic or extracellular side of PM  Often transiently interact with PM eg. response to signals o Lipid-anchored proteins: can be on cytoplasmic or extracellular side (anchored on wither side)  On the extracellular side, proteins are attached to a complex oligosaccharide linked to a phosphatidylinotisol t form GPI glycophosphatidylinisol linked proteins eg. some receptors such as prion x Membrane fluidity depends on: o Temperature o The types of lipids o The presence of cholesterol tdisrupts the packing of fatty acid chain x Transition temperature = the greater the degree of unsaturation, the lower the temperature beore the bilayer gels; eg. butter gels at higher temp than oil; more trans fats in oil than butter x Various factors influence the mobility of integral membrane proteins o Local crowding of proteins; neighbours restrict movement www.notesolution.com o Barriers on the cytoplasmic side of the membrane o Interaction with the extracelleular material x The movement of solutes through diffusion; if substance is a charged ion, diffusion affected by the difference in charge between the compartments (opposites attract); energetically favoured if compartments have opposite charges referred to as the electric potential gradient x Osmosis = water moves froma region of low solute concentration to a region of high solute concentration o Hypoosmotic solution with low solute conc: water enters cell, cell swells o Hyperosmotic solution with high solute conc: water leaves cell, cell shrinks o Isoosmotic solution with equal solute conc. In solution and inside cell x Types of gated ion-channels o Voltage gated: opening is dependent on the difference of ionic charge between the 2 sides of the membrane eg. K+ ion channel o Ligand-gated: the binding of a specific molecule/ligand opens and closes the channel to ions eg. acetylcholine neurotransmitter binds to the outside of the channel x Facilitated diffusion; regulation of glucose transporters o Blood sugar level low tinsulin low t GLUT 4(=transporter) in cytoplasmic vesicles(endocytosed) t few transporters on PM t very little internalization of glusocse into cells o Blood sugar level is high, insulin high, insulin binds to insulin receptors on PM = signal for vesicles to exocytose GLUT4 Æ more transporter on PM Æmore internalization of glucose into cells x Active transport similar to facilitative transporter in that binding if the molecule to the pump results in a conformational change that allows the molecule to be delivered to the other side of the membrane www.notesolution.comLECTURE#5 N A function of the plasma membrane is that it serves as a scaffold fro biochemical activities eg. signalling proteins send signals to the nucleus N It allows the cell to respond to extracellular signals eg. signals could tell cels to prepare for cell division ; cell surface receptors that bind ligand on the cell exterior can send signals into the cytoplasm of the cell N PM is a lipid bilayer N Hydrophobic interactions of the fatty acid tails of the PM N Protein channels within the bilayer N Short sugar chains on proteins and lipids are called glycoproteins or glycolipids N Membrane lipids are amphipathic, contain both hydrophobic and hydrophilic regions; 3tyes o Phospholipids o Sphingolipids o Cholesterol N Sphingolipids are composed of an amino alcohol with a long hydrocarbon chian called sphingosine and a single fatty acid chain; fatty acid is attached to the amino group of sphingosine; ceramide is the simplest sphingolipid N Glycolipids are formed when a sugar is attached to the terminal alcohol of a sphingosine; certain viruses and txins eg. cholerainfluenza toxins bind to cell surface glycoproteins and gain access to cells N 3 types of membrane proteins o Integral membrane proteins: transmembrane protei
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