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Transcript
Membrane Transport • There are many molecules on (peripheral), within (trans), and inside (intracellular) the cell membranes. These all aid in getting necessary molecules into and out of the cell. They also play a role in cell to cell communication. • Most are proteins with or without carbohydrates or lipids attached These structures make membrane Selectively permeable • : The cell membrane acts like a wall around the cell but it does have pores that act like doors (see page 97) • Some molecules are brought into the cell and it TAKES energy to do this. ACTIVE TRANSPORT • Some molecules can flow through without costing the cell any energy. PASSIVE TRANSPORT Passive Transport & examples • Osmosis: The movement of water from High to low concentrations.Aquaporins for diffusion of water, • Filtration: process that is driven by hydrostatic pressure (pressure from water) it drives particles in and out of cell • Blood pressure forces fluid through gaps in capillary walls • Water, salts, nutrients are transferred from blood to tissues . • Diffusion of molecules from High to Low conc • O2 from the air to blood • Facilitated diffusion: Uses carrier proteins but does not use energy. Active Transport and examples • Carrier Mediated Transport: TAKES energy to do this!!! Usually in the form of ATP • This can pump a molecule AGAINST the gradient!!! • Sodium/Potassium pump 3 Na out, 2K in • • • • • • Half your daily calories are used for this alone!!!!!! Why so important?? THIS PUMP: 1. Regulates cell volume 2. Provides secondary active transport via generating electricity to pump other things..kidney function or Sodium Glucose transport 3. Heat production(thyroid stimulates na/k pump production..raising heat 4. Maintenance of membrane potential(Imp. In nerve function) • Vesicular Transport: TAKES energy • Endocytosis, exocytosis, phagocytosis, pinocytosis Most important Pumps • Sodium-potassium pumps(Na-K): this pump burns one ATP to push 3 Na+ out of cell and 2 K+ into the cell • Sodium-glucose transport protein(SGLT): binds Na+ and glucose outside of cell. Uses ATP and Na+ gradient to push glucose into cell • ATP synthetase: As Na+ enters the cell ATP is made from ADP and P+ Diffusion • Diffusion: the process of particles, nutrients, molecules, salts moving from high to low concentration to achieve a balance • Concentration Gradient: when the concentration of a particle is higher in one area then another Osmolality • Osmolality is the amount of solute (stuff) in a solution. • HYPO-tonic solution= has a LOW concentration of solute compared to that inside the cell High conc of water • HYPER-tonic solution= has a HIGH concentration of solute compared to that inside the cell Low conc of water • ISO-tonic solution= has equal conc of water is same as the cell. Movement of water • Osmosis: the process of water moving from low solute(High Water) to high solute (Low Water)through a selectively permeable membrane • Osmotic Pressure: the force that stops osmosis due to filtration.(the flow of water across the membrane due to it’s own weight = the flow of water due to osmosis • http://www.mhhe.com