Roxanita
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An experiment was conducted to study diffusion across the nerve cell membrane. Electrophysiologic measurements in several different nerve cells were conducted in response to the addition of several different particles.
Diffusion would most likely be increased by which of the following?
a) Decreased concentration Gradient
b) Decreased electrical Gradient
c) Decreased membrane surface area
d) Increased membrane thickness
e) Lipophilic particles
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| MLF
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E) Lipophillis particles?
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| Roxanita
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for me the correct answer is E)
The plasma membrane is composed of lipids and can be easily penetrated by lipophilic molecules. Therefore, the more lipid soluble a molecule, the easier it will cross the membrane.
Decrease Concentration Gradient (choice A) and decrease Electrical Gradient (choice B) would decrease the Driving Force behind molecule movement. Molecules move from high concentration to low concentration. The closer a molecule gets to equilibrium, the less the driving force for movement across the membrane. Molecules also move toward the side of the opossite charge. Like the concentration gradient, the more similar the two sides are electrically, the less force will be driving molecule movement.
Decreased Membrane Surface Area (choice c) is incorrect because this would decrease the space available for particle diffusion.
This can be illustrated by Fick's Law, which states that:
J=-DA x (C1-C2) / DX
J= flow of solute, D= diffusion coefficient of the solute, A=surface area through which flow is measured, C= concentration of the solute, and DX=distance between regions 1 and 2.
Therefore a reduction in A would decrease flow (J).
Also increased membrane thickness (choice D) is incorrect answer because Fick's Law shows that an increase in Membrane Thickness (DX) decreases solute flow.
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"We all basically have 2 choices in life: Let things stay the way they are or work to make them better"
-Julia Havey
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