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cell membrane q& a

cell memb q&a /bio 101

QuestionAnswer
What is the main function of the lipid bilayer? The lipid bilayer acts as a barrier between the inside and outside of the cell. It is highly impermeable and does not allow most molecules to freely pass through it into or out of the cell.
Why is the structure called a lipid bilayer? It is called a lipid bilayer because it is composed of two layers of fat, or lipid, molecules.
A phospholipid molecule contains two distinct regions. The __________ region is attracted to water and the ___________ region is repelled from water. As a result of its both polar and nonpolar regions, it is classified as a(n) __________ molecule. Hydrophilic. Hydrophobic. Amphipathic.
Are the two layers of the lipid bilayer identical in composition? No. As a result of the bilayer's fluidity, structures such as lipids and proteins can freely move around within the lipid bilayer.
Will you find the same set of membrane proteins in each cell membrane? No. Membrane proteins perform a number of functions within cells, as a result, different proteins are necessary in different regions of cells depending on the function of the cell and the interactions it may take part in.
What are the names of the two main classes of membrane proteins ? The two main classes of membrane proteins are integral versus peripheral proteins.
How could you tell the difference of integral protiens vs peripheral protiens? Since peripheral proteins are easily dissociated from the lipid bilayer, one could treat a cell with a mild detergent that does not disrupt the cell membrane and then see if the specific protein remains associated with the lipid bilayer or is removed.
What is the name of the configuration that membrane proteins adopt in regions that span the lipid bilayer? This configuration is called an alpha-helix. It is the same structure that DNA adopts naturally.
Which class of proteins, integral or peripheral, are freer to move around within the lipid bilayer? Integral proteins can be thought of as icebergs that float in a lipid bilayer sea. They are relatively mobile in the cell membrane.
The cell surface is covered with an additional set of molecules. What name is given to these structures and what is their function in the cell? The cell surface is covered with a cell coat or glycocalyx which consists of carbohydrate chains. They help protect the cell from damage.
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.
What is the name of the natural process by which molecules flow from an area of higher concentration to one of lower concentration? Diffusion.
What is the behavior of carrier 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.
What is the behavior of channel proteins? 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.
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.
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.
Created by: vcopeland
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