Q. Why can channel and carrier proteins carry only one kind of molecule through the cell membrane?
Channels are very selective and will accept only one type of molecule (or a few closely related molecules) for transport. Passage through a channel protein allows polar and charged compounds to avoid the hydrophobic core of the plasma membrane, which would otherwise slow or block their entry into the cell.
Q. How do carrier proteins move molecules through the lipid bilayer?
Carrier proteins bind specific solutes and transfer them across the lipid bilayer by undergoing conformational changes that expose the solute-binding site sequentially on one side of the membrane and then on the other.
Q. What is the structure of carrier proteins?
Each carrier protein has a specific role. The sequence of the chains of amino acids defines the specific shape and function of the protein. Each carrier protein accepts only one molecule. The molecule is attached to the carrier protein, and the carrier changes shape moving the molecule into the cell.
Q. Which substance use is a carrier protein to cross the plasma membrane by facilitated diffusion?
Facilitated diffusion uses integral membrane proteins to move polar or charged substances across the hydrophobic regions of the membrane. Channel proteins can aid in the facilitated diffusion of substances by forming a hydrophilic passage through the plasma membrane through which polar and charged substances can pass.
Q. Which substance requires a protein carrier in order to cross a membrane?
118 Cards in this Set
| hypotonic solution is one whose concentration is… | less than that inside the cell |
|---|---|
| Name substances that require a protein carrier to cross the cell membrane | water, glucose, sodium ion, an amino acid |
| What substance fails to cross cell membranes under any circumstances? | DNA |
Q. What fails to cross cell membranes?
Polar and charged solutes will not cross cell membranes effectively without specific protein carriers. Large molecules, such as proteins, usually are not transported across cell membranes. e. Ions are typically transported by special proteins that form membrane channels.
