CHAPTER 11: MEMBRANE STRUCTURE AND FUNCTION 1) In considering the movement of small molecules across a lipid bilayer, the permeability coefficient can be correlated with C. 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. 2) The most common way in which integral membrane proteins span the membrane is in B. α-helical segments. -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.) 3) Which membrane component exhibits the fastest movement within the bimolecular sheets? A. Phospholipids undergoing lateral diffusion.-Within membranes, phospholipids can travel along one side of the bimolecular sheet very rapidly, in a process called lateral diffusion 4) Which of the following factors makes the membrane environment more ordered and less fluid? B. 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. 5) In passive transport (also known as facilitated diffusion), the energy driving the movement of materials across a membrane is provided by C. 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 6) The Na +-K + pump is an active transport system that A. 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 7) Which of the following is NOT true regarding P-type ATPases? B. 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 8) Secondary transporters (or cotransporters) can be divided into symporters and antiporters. What is the basis for this distinction? A. 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 9) Which of the following is NOT true of ion channels? B.
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