-50 -100 -150 Glutamate + Mg²+ -100 Glutamate, no Mg2+ -50 0 50 Membrane potential (mV) 100 Mg2+ only allows positive ion to enter the cell, causing an inward negative current. The Mg2+ block of the NMDA receptor is removed at this voltage and positive ions leave, causing an outward positive current. Previous O Mg2+ only allows positive ions the to leave the cell, causing an outward positive current. O NMDA receptor with Mg2+ bound is closed at very negative potentials. O The Mg2+ block of the NMDA receptor is removed at this voltage and positive ions enter, causing an inward negative current. Next ▸ Based on the same attached figure as in question 1 above (Figure 6.8A-B in your textbook) describing the NMDA receptor, a ligand-gated ion channel for glutamate, why does the current versus voltage response described by the red line go from near zero to a negative current at around -50 mV? (A) Channel pore Glutamate Mg2+ (B) EPSC (PA) 150 100 50 0 -50 -100 -150 Hyperpolarized, Mg2+ blocks ORA Glutamate + Mg2+ 0/ + Na Ca²+ Glutamate, no Mg2+ Depolarized, no Mg2+ block while K+ 100 Mg2+

-50 -100 -150 Glutamate + Mg²+ -100 Glutamate, no Mg2+ -50 0 50 Membrane potential (mV) 100 Mg2+ only allows positive ion to enter the cell, causing an inward negative current. The Mg2+ block of the NMDA receptor is removed at this voltage and positive ions leave, causing an outward positive current. Previous O Mg2+ only allows positive ions the to leave the cell, causing an outward positive current. O NMDA receptor with Mg2+ bound is closed at very negative potentials. O The Mg2+ block of the NMDA receptor is removed at this voltage and positive ions enter, causing an inward negative current. Next ▸ Based on the same attached figure as in question 1 above (Figure 6.8A-B in your textbook) describing the NMDA receptor, a ligand-gated ion channel for glutamate, why does the current versus voltage response described by the red line go from near zero to a negative current at around -50 mV? (A) Channel pore Glutamate Mg2+ (B) EPSC (PA) 150 100 50 0 -50 -100 -150 Hyperpolarized, Mg2+ blocks ORA Glutamate + Mg2+ 0/ + Na Ca²+ Glutamate, no Mg2+ Depolarized, no Mg2+ block while K+ 100 Mg2+

Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter32: The Reception And Transmission Of Extracellular Information

Section: Chapter Questions

Problem 8P

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The top panel (a) of this figure shows the graded potential change (far right, upper, electrical trace) that results from ligand binding to the ligand gated Na+ channel. The bottom panel of this figure (b) shows a graded potential change (far right, lower, electrical trace) that results from ligand binding to a ligand gated Cl- channel. From this trace you know (Vm = -70 mV) 1. ECl- is -70 mV 2. ECl- is more negative than -70 mV (i.e., -80 mV) 3. ECl- is more positive than -70 mV (i.e., -60 mV)
Cone snails are carnivores that inject a powerful set of toxins into their prey, leading to rapid paralysis. Many of these toxins are found to bind to specific ion-channel proteins. Why are such molecules so toxic? How might such toxins be useful for biochemical studies?
Crystal structures of neurokinin-1 with pdb codes 6hll, 6hlo, 6hlp. Which is the highest quality crystal structure?
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Consider the transport of K+ ions from a surrounding fluid (where [K + ] = 30 mM) into a cell (where [K + ] = 420 mM) where the membrane electrical potential is -0.15 V. Is this process favorable?
Neutral sphingomyelinase 2 converts sphingomyelin into ceramide and phosphorcholine. What kind of enzyme is it? Assume Vmax is 35 µM min-1. When you provide 3.0 x 10-5 M of sphingomyelin, you observe an initial velocity of 6.0 µM min-1. Calculate the KM.
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serotonin [µM] 0.025 transport rate A [dpm/min] 300.0 transport rate B [dpm/min] 10 0.08 920.0 30.0 0.25 2500.0 100.0 0.7 5400.0 350.0 2 8800.0 1100.0 9100.0 3000.0 11. Draw a graph (by using Excel or similar), plotting the serotonin concentration against the transport rate under both conditions. 12. What transport rates for each condition would you expect if the experiment was repeated using 12µM ['H] serotonin? Add your estimate into the table above. 13. Examine the plot obtained for condition A; what can you conclude with regards to whether or not the transport of serotonin into these cells requires a protein? Explain your conclusion.
serotonin [µM] 0.025 transport rate A [dpm/min] 300.0 transport rate B [dpm/min] 10 0.08 920.0 30.0 0.25 2500.0 100.0 0.7 5400.0 350.0 2 8800.0 1100.0 9100.0 3000.0 11. Draw a graph (by using Excel or similar), plotting the serotonin concentration against the transport rate under both conditions. 12. What transport rates for each condition would you expect if the experiment was repeated using 12µM ['H] serotonin? Add your estimate into the table above. 13. Examine the plot obtained for condition A; what can you conclude with regards to whether or not the transport of serotonin into these cells requires a protein? Explain your conclusion. 14. Compare the plots of the transport rates for both conditions. What is most likely mechanism of transport for serotonin into these cells? Explain your interpretation.
If instead of using 3.5 µM myoglobin (receptor) you used half of this (that is, 1.75 µM myoglobin), what would be that value of the Kd, that you calculated ( how would it change)? Please explain so I can solve on my own :) (How does changing concentration of the receptor in a ligand-receptor binding experiment affect the dissociation constant?)
The sarcoplasmic reticulum Ca2+-ATPase, pumps 2 mol Ca2+ out of sarcomeres per mol ATP hydrolyzed.(a) Given the following steady-state concentrations and a membrane potential of 65 mV (inside negative), calculate ΔG for the following activetransport process at 37 °C and pH = 7.4:2Ca2+(in) + ATP + H2O → 2Ca2+(out) + ADP + Pi + H+ATP = 2.6 mM, ADP = 210 μM, Pi = 5.1 mM, Ca2+(in) = 32 mM,Ca2+(out) = 2.2 mM(b) In active muscle the pH can drop below 7.4. Is the reaction above moreor less favorable under these conditions?(c) The activity of the Ca2+-ATPase is regulated reversibly under normalconditions to maintain homeostatic concentrations of Ca2+ inside thesarcomere. However, in a rare genetic disorder, irreversible activation ofthe Ca2+ -ATPase can occur. Assuming 37 °C, pH = 7.4, and the steadystate concentrations for ATP, ADP Pi, and Ca2 +(out) given in part (a),calculate the minimum [Ca2 +] inside a sarcomere that has irreversibly activated Ca2 +-ATPase (i.e., the Ca2 +-ATPase…
The NMDA receptor is described as a "coincidence detector" allowing it to detect concurrent activities in the pre- and postsynaptic cells. What are the 2 biochemical properties of the NMDA receptor that allow it to detect concurrent activities in the pre- and postsynaptic cells?