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BIO1000- Notes TEST2 FRI NOV 8.docx

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York University
BIOL 1000
Megan Hillman

Chapter 5 Membranes and Signalling continued see previous notePeripheral Proteins Attached to one hydrophillic side either intracellular or extracellular Primarily found on cytosolic intracellular side Attach via noncovalent bonds easy to detach Can attach via integral protein or lipid anchor or directly with lipid moleculesOn surface of membraneDo not interact with hydrophobic coreHeld together by noncovalent bondsMost on cytoplasmic side of membraneMade up of mixture of polar and nonpolar amino acids Ligand signaling molecule sent from signaling cell2 Categories of Proteins Integral Proteins Inserted into the membrane Must interact with polar and nonpolar region of membrane therefore are amphipathic Must have a nonpolar region for interaction with the hydrophobic nonpolar region of the membrane Difficult to remove TRANSMEMBRANE PROTEINS Most common integral proteins Cross entire membrane from extracellular to intracellular space Integral Membrane ProteinsProteins embedded in phospholipid bilayerComposed of predominantly nonpolar amino acids usually coiled into alpha helicesTransmembrane proteins Most integral proteins aquaporin polytopic goes through the entire membraneTonicity of a solution relative to and in comparison to another solution knowing tonicity of a solution is relative to another solution Determines direction of water flow osmosis Hypertonic solute high relative to the solution hypotonic solute low relative to solution isotonic Osmosis Can be compared in two different ways Hypotonic low solute on outside relative to inside hypertonic high solute on outside relative to inside Hyponatraemia overloading cells with liquid disrupt electrolyte balance low salt concn Dieretic to remove water and supplement saltlow to high concentrationActive transport against the gradient requires energy in the form of ATP Na K H gradients so that passive facilitated or not diffusion can occur when necessary Primary Active transport pumps cations positive charge against the gradient to maintain or create stronger gradient Conformational changes helps maintain Membrane potential refers to the difference between the inside charge and outside charge difference is a negative value 50mv to 200mv Overall the charge insidethe cell is more positive than outside more negativeSodium potassium pump help set up overall negative inside and overall positive outside the cell to transmit nerve signals down axons At restMove 3 sodium ions out of the cell and two potassium into the cellBind to sodium proteinphosphorylation causes pump to change conformation so that Na binding sites are exposed to opposite side of membrane and 3 NA are released to the fluid outside the cell where Na concentration is high as affinity of Na binding site greatly decreasesWhen 2 potassium form the fluid outside the cell where K concentration is low bind to the pump Dephosphorylation release of phosphate group conformation changes to the original conformation and causes the pump to revert to its original conformationBINDING SITES3 for sodium and 2 for potassiumamino acids causes the negative charge inside Secondary driving ion high to low High concentration set up by active primary driving ion will move down its concentration high to low drives the blue ones to move against concentration gradient low to high Two K are released into cytosol where K is high as affinity of K binding sites markedly decreases during change in shape At the same time affinity of Na binding sites greatly increases returning to step oneSymport the cotransported solute moves through the membrane channel in the same direction as the driving ion a phenomenon known as cotransportamino acids glucose Antiport concentration of the driving high inside low outside one into the cell and one out of the cellRED BLOOD CELLS driving ion moves through the membrane channel in one direction providing the energy of active transport of another molecule in the opposite direction Process called exchange diffusionOSMOSIS RULEwater will move from low to high concentration toward hypertonic portionENDOCYTOSIS Pinocytosis drinking cell bulk phase endocytosis not specific Receptor mediated endocytosis vesicle forms as a result from specific proteins outside the cellClathrin coats outside of vesicle causing it to form clathrin interacts with receptors molecules will bind to receptor Due to forming of clathrin will cause the vesicle to bud inward All proteins are brought into the cell Phagocytosis autophagocytosis digesting own components Phagocytosis prey and larger particles can be taken in Lobes surround brey and close around it and prey is enclosed vesicle forms due to engulfment and then transports the substance to lysosomesExtra cellular intercellular between cells direct conntach attrachted or touching plasmodesmata gap junctions local situatioed ear each other long distance situated far awayDictyostelium slime mold cells attracted to each other aggragating Chemotaxis the chemical is detected to single cell slime mold amoeba and releases a chemical trail for other slime mold cells to followControlling signalling cell synthesizes specific molecule that affects activity of target cell hormones and neurotransmitters small proteins Target cell receives the signal released from the controlling cellBinds to receptor protein specific to a certain protein intergral move signal from outside to inside MUST CROSS BOTH PARTS
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