CHAPTER 11: MEMBRANE STRUCTURE AND FUNCTION
In considering the movement of small molecules across a lipid bilayer, the permeability
coefficient can be correlated with
the solubility of the molecule in a nonpolar solvent.
The greater the solubility in a nonpolar medium, the more rapidly a molecule crosses
a lipid bilayer.
The most common way in which integral membrane proteins span the membrane is in
Alpha helices offer an energetically favorable way for a protein to span the membrane
in terms of having hydrophobic R-groups on the outside and the polar peptide bonds
hydrogen bonded together on the inside.)
Which membrane component exhibits the fastest movement within the bimolecular
Phospholipids undergoing lateral diffusion.
Within membranes, phospholipids can travel along one side of the bimolecular sheet
very rapidly, in a process called lateral diffusion
Which of the following factors makes the membrane environment more ordered and less
the presence of cholesterol
Cholesterol makes eukaryotic membranes less fluid. The bulky ring structure of
cholesterol interferes with the typical motions of the fatty acid tails of phospholipids.
In addition, cholesterol appears to have some specific interactions with certain
components (such as sphingolipids), forming less mobile raft-like complexes.
In passive transport (also known as facilitated diffusion), the energy driving the
movement of materials across a membrane is provided by
the concentration gradient across the membrane
Materials move from regions of high concentration to low concentration with the
driving force being the concentration gradient itself
pump is an active transport system that
pumps sodium ions out of the cell and potassium ions into the cell
Because the movement of each ion is against its concentration gradient, energy is
needed to move them in the direction indicated
Which of the following is NOT true regarding P-type ATPases?
Because of their common mechanism, they lack specificity and a given P-type ATPase
can often transport different ions or molecules
This statement is not true. Although they share a common mechanism, each different
P-type ATPase has a high specificity for the particular molecule transported
Secondary transporters (or cotransporters) can be divided into symporters and antiporters.
What is the basis for this distinction?
Symporters use the energy from one molecule moving down its concentration gradient to
drive the movement of a second molecule in the same direction against its concentration
gradient while antiporters drive the movement in the opposite direction
This correctly defines the difference between symport and antiport systems
Which of the following is NOT true of ion channels?
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