Chapter 12: Transport Across Cell Membranes Flashcards
The ______ the molecule and the more __________, the more rapidly it will diffuse across the lipid bilayer
smaller, hydrophobic
What is the term for a substance that dissolves in water
solutes
T/F lipid bilayers are highly impermeable to all charged substances no matter how small
True
Name the most plentiful cation outside the cell
Na+
Name the most plentiful cation inside the cell
K+
The high concentration of Na+ outside the cell is electrically balanced by ____
Cl-
What are the two main classes of membrane transport proteins?
Channels and transporters
How do channels discriminate what goes through the lipid bilayer?
mainly on the basis of size and electrical charge:
when the channel is open, only ions of an appropriate size and charge can pass through.
How do transporters discriminate what goes through the bilayer?
Transfers only molecules or ions that fit into specific binding sites on the protein.
How do some freshwater protozoans eliminate excess water?
Through contractile vacuoles that periodically discharge their contents to the exterior
T/F Passive transporters move a solute along its electrochemical gradient
True
How many times does the glucose transporter cross the cell membrane?
12 times
What are the 3 ways that transmembrane pumps carry out transport in the cell?
- gradient-driven pumps:
these link the uphill transport of one solute across a membrane to the downhill transport of another - ATP-driven pumps use the released energy released by the hydrolysis of ATP to drive uphill transport
- light driven pumps: mainly in bacterial cells, use energy derived from sunlight to drive uphill transport
what would happen if an atp-driven Na+ pump ceased operating?
everything would shut down
How do plant cells, fungi and many bacteria use ATP driven H+ pumps?
by pumping H+ out of the cell, these proteins create an electrochemical gradient of H+ across the plasma membrane
