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Cell Membranes

Problems

Structures Responsible for Membrane Transport

How to Cite This SparkNote

Problem : Why is it necessary for cell membranes to have proteins that help transport molecules?

The cell membrane is composed of a lipid bilayer that is highly impermeable to most molecules. As a result, outside structures are required to help transport essential large, polar molecules across the cell membrane.

Problem : What is the name of the natural process by which molecules flow from an area of higher concentration to one of lower concentration?

Diffusion.

Problem : What is the difference between the behavior of carrier and channel proteins?

Carrier proteins allow specific molecules to cross the cell membrane by undergoing a conformational change upon the binding of the molecule. The conformational change opens a hole through which the molecule can enter or exit a cell. Channel proteins do not require the binding of a molecule and conformational change to open. Channel proteins allow molecules to steadily diffuse across the membrane through diffusion.

Problem : What is the function of an ionophore?

Ionophores function to increase a membrane's permeability to a specific ion thereby facilitating its movement across that cell's membrane.

Problem : Name two specific functions of membrane transport.

Membrane transport helps maintain the proper distribution of ions across a cell membrane; helps maintain proper cellular pH, and helps mediate communication between cells in multi-cellular organisms.

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