Biochemistry
6th Edition
ISBN: 9781305577206
Author: Reginald H. Garrett, Charles M. Grisham
Publisher: Cengage Learning
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Question
Chapter 32, Problem 7P
Interpretation Introduction
Interpretation:
The acetylcholine concentration in the synaptic vesicle needs to be calculated.
Concept Introduction :
The shape of a vesicle is like the shape of a cylinder thus its volume can be calculated as follows:
Here, r is radius of the base of the cylinder.
The concentration is calculated as number of moles present in 1 L of the solution.
It is mathematically represented as follows:
From the given
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Myasthenia gravis is a disease that leads to a marked decrease in the number of acetylcholine (Ach) receptors at the neuromuscular junction. As a result, suppose only about 200 (instead of 2000) Ach receptor-channels are opened by each quantum of Ach. The Ach-gated channels that survive operate normally and each cause a depolarization of about 0.25 x 10-3 mV when open. The function of the presynaptic terminal is normal and an action potential will cause the release of 100 quanta of neurotransmitter.
Part a.) For a patient with myasthenia gravis, what would be the size (in mV) of a miniature excitatory post-synaptic potential (or that associated with one quantum of Ach)?
a.) 0.05 mv
b.) 0.25x10-4 mv
c.) 0.25x10-3 mv
d.) 0.5x10-3 mv
e.) 0.5 mv
Part b.) For a patient with myasthenia gravis, what would be the size (in mV) of the full excitatory post synaptic potential consequent to the entry of an action potential into the presynaptic terminal of the neuromuscular junction?
a.) 70 mv…
Myasthenia gravis is a disease that leads to a marked decrease in the number of acetylcholine (Ach) receptors at the neuromuscular junction. As a result, suppose only about 200 (instead of 2000) Ach receptor-channels are opened by each quantum of Ach. The Ach-gated channels that survive operate normally and each cause a depolarization of about 0.25 x 10-3 mV when open. The function of the presynaptic terminal is normal and an action potential will cause the release of 100 quanta of neurotransmitter. For a patient with myasthenia gravis, what would be the magnitude of the depolarization (in mV) associated with opening of one Ach-gated channel?
a.) 0.25x10^-2 mv
b.) 0.25x10^-3 mv
c.) 0.25x10^-4 mv
d.) 0.5x10^-1 mv
e.) 0.5 mv
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+
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- Mechanism of action of depolarizing and nondepolarizing Neuromuscular Blockers (NMBs)arrow_forwardCalculate the equilibrium membrane potentials to be expected across a membrane at 37 ∘C, with a NaCl concentration of 0.50M on the "right side" and 0.08 M on the "left side", given the following conditions. In each case, state which side is (+) and which is (−). (a)Membrane permeable only to Na+.arrow_forwardSome cells with very negative resting membrane potentials, like -80 mV, express an the inward rectifier K+ channel. Describe the channel/ conductance.arrow_forward
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- Calculate the equilibrium membrane potentials to be expected across a membrane at 37 ∘C, with a NaCl concentration of 0.50M on the "right side" and 0.08 M on the "left side", given the following conditions. In each case, state which side is (+) and which is (−). Membrane permeable only to Cl−.arrow_forwardOne of the important uses of the Nernst equation is in describing the flow of ions across plasma membranes. Ions move under the influence of two forces: the concentration gradient (given in electrical units by the Nernst equation) and the electrical gradient (given by the membrane voltage). This is summarized by Ohms law: Ix=Gx(VmEx) which describes the movement of ion x across the membrane. I is the current in amperes (A); G is the conductance, a measure of the permeability of x, in Siemens (S), which is I/V;Vm is the membrane voltage; and Ex is the equilibrium potential of ion x. Not only does this equation tell how large the current is, but it also tells what direction the current is flowing. By convention, a negative value of the current represents either a positive ion entering the cell or a negative ion leaving the cell. The opposite is true of a positive value of the current. a. Using the following information, calculate the magnitude of Na [ Na+ ]0=145mM,[ Na+ ]i=15mM,Gna+=1nS,Vm=70mV b. Is Na+ entering or leaving the cell? c. Is Na+ moving with or against the concentration gradient? Is it moving with or against the electrical gradient?arrow_forwardThe resting membrane potential of a neuron typically is 70 mV. What does this mean?arrow_forward
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