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Exam 1 Study Guide Membrane Transport Lecture 1 Chapter 6 Understand the processes of diffusion and osmosis and the mechanisms of carrier protein mediated transport across the cell membrane o Diffusion Due to random movement thermal energy solute molecules will show net movement from region of high concentration to region of low concentration solute moves down concentration gradient Rate of Diffusion increases with temperature increases with concentration gradient increases with surface area of membrane decreases with distance o Osmosis Diffusion of water across a semipermeable membrane water moves from low solute concentration solution to high solute concentration solution from regions with high water concentration to low water concentration o Carrier protein mediated transport Facilitated diffusion Transported molecule is moved down its concentration gradient Does not require extra energy from the cell uses potential energy of concentration gradient transport is regulated by increasing or decreasing the number of transporters in a cell Primary active transport Membrane carrier protein is an ATPase that breaks down ATP to release energy Energy is used to transport molecule against its concentration gradient Ca 2 ATPase pump and Na K ATPase pump Secondary active transport coupled transport Co transporter allows molecule 1 to move down concentration gradient couples energy of first molecule to co transport molecule 2 up its gradient Be able to recognize if transport is mediated by carrier proteins and whether it is active or passive transport o Passive transport is diffusion or osmosis o Active transport are mediated by carrier proteins and are facilitated diffusion active transport and coupled transport Be sure to understand how to determine the net ow of water during osmosis o Net flow of water during osmosis is determined by osmotic pressure Osmotic Pressure is how strongly a concentrated solution pulls water by osmosis across the membrane Pure Water osmotic pressure 0 Equal osmotic concentration on each side isotonic less concentrated solution lower osmotic pressue hypotonic More concentrated solution higher osmotic pressure hypertonic o Determine osmotic pressure with osmolality Osmotic concentration is measured in Osmolality Osm number of particles in moles liter water Osmosis is diffusion of water from low osmolality to high osmolality If the osmolality of the inside of the cell is higher than the solution than the flow of water is into the cell and it is hypertonic Remember particles suck Membrane Potential Lecture 2 Chapter 6 Memorize the Nernst Equation as given in the textbook p 148 Be able to calculate the equilibrium potential for an ion you will be given the concentration of the ions on the exam but you need to be able to apply the Nernst Equation o Eion equilibrium potential in millivolts mV for ion x o ion out concentration of the ion outside the cell o ion in concentration of the ion inside the cell o Charge valence of the ion so 1 for Na 90 mV Equilibrium charge for common molecules EK 61 1 log 5 mM 125 mM ENa 61 1 log 150 mM 15 mM ECl 61 1 log 125 mM 10 mM ECa 61 2 log 25 mM 0002 mM 136 mV 61 mV 61 mV You do NOT need to memorize the Goldman equation but you should understand how the membrane permeability of the different ions contributes to resting membrane potential o The resting membrane potential is dependent on the most permeable ion Understand the role of the Na K pump to maintain Na and K concentrations in and out of the cell o The concentrations of K and Na are maintained constant because of the constant use of energy in active transport by the pumps The Na K pumps transports 3 Na out of the cell for every 2 K that moves in As a result the resting membrane potential in absence of stimulation in nerves and muscles is 70mV Neurons Lecture 3 Chapter 7 Know the basic anatomy parts of a neuron e g Fig 7 2 7 6 o Cell body Nucleus endoplasmic reticulum Golgi apparatus etc o Dendrites branches Inputs of the neuron Many sensory receptors or other neurons release chemical signals onto receptor molecules in the dendrites o Axon Output of the neuron of neuron to target cells o Synapses Long fiber extending up to meters to carry output signal action potential connections between the axon of a neuron presynaptic cell with a target cell postsynaptic cell o Postsynaptic target cell could be another neuron or it could be muscle or gland cells Know the basic functions of glial cells astrocytes schwann cells and oligodendrocytes o glia glue Support cells for neurons Provide electrical insulation nutrition and growth factors to neurons o Astrocytes star shaped Provide nutrition to brain spinal neurons Take up glucose from blood convert to lactate released for neurons Remove excess K and neurotransmitters from intracellular space In the CNS convert glucose to lactate and release lactate for neurons to use Also remove excess K neurotransmitters released by neurons from intracellular fluid o Schwann insulate peripheral axons form sheath around axons of peripheral nerves Transected peripheral nerves can regrow along nerve sheath to re innervate target tissue Central nerves can not regenerate degenerate in multiple sclerosis contain myelin a fatty insulating compound white matter of brain o Oligodendrocytes many branches insulate brain spinal neurons Degenerate in multiple sclerosis contain myelin a fatty insulating compound white matter of brain Understand the phases of the action potential and the timing and role of voltage gated Na and K channels during the action potential and the refractory periods 1 Depolarization by electrical stimulation or neurotransmitter 2 Vm rises above AP threshold depolarization 3 Voltage gated Na channels open Vm moves to ENa 4 Rising Vm depolarizes neighboring membrane AP starts moving down axon speed depends on cable properties 5 Voltage gated Na channels inactivate Voltage gated K channels open Vm moves to EK 6 Voltage gated K channels close Vm returns to resting potential Understand how action potentials code for stimulus intensity o If Vm is kept above threshold then neuron fires multiple action potential but each Action Potential is the same size So duration of firing of Action Potentials duration of stimulation o The stronger the stimulation the faster the neuron fires Action Potentials So frequency of Action Potentials strength of stimulation Remember what tetrodotoxin TTX does o Found in the pufferfish blocks voltage gated Na channels


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FSU PCB 3743 - Membrane Transport

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