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Cell Membranes Problem Set

Problem 7: Diffusion

Tutorial to help answer the question


Crossing a membrane by easy diffusion can be distinguiburned from helped with diffusion because:

A.
Simple diffusion does not require energy: promoted diffusion needs a source of ATP.

You are watching: Unlike simple diffusion, facilitated diffusion requires energy expenditure by the cell.

B. Simple diffusion can only move material in the direction of a concentration gradient; promoted diffusion moves products through and versus a concentration gradient.
C. Simple diffusion is not saturable; facilitated diffusion rates are restricted by the variety of useful membrane proteins and can be saturated*
D. Simple diffusion is discovered only in prokaryotes while helped with diffusion is uncovered only in eukaryotes.

Tutorial

Diffusion

Diffusion suggests that the net activity of pposts (molecules) is from an area of high concentration to low concentration.
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If the pposts have the right to move through the lipid bilayer by basic diffusion, then tright here is no limit to the number that can fit through the membrane. The price of diffusion boosts lipractically as we include more particles to one side of the membrane.

If the pposts can just pass through protein networks, then the price of diffusion is determined by the variety of networks as well as the number of particles.

See more: Broken Bells - Holding On For Life, Holding On For Life By Broken Bells

Once the channels run at their maximal rate, a additionally rise in pshort article numbers no longer rises the noticeable rate of diffusion. At this limited price we explain the protein channel as being saturated.

The cartoon illustprices numerous points around facilitated diffusion. The pwrite-ups are more focused on one side of the membrane, and yet they can relocate in both directions. However, the net motion is from high pshort article concentration to low. If the number of pwrite-ups gets so high on one side of the membrane that they interfere with diffusion via the protein channel, then we observe a limit to the rate of diffusion at the suggest of saturation.


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computer animation provided with permission of the Virtual Cell Internet Page
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