Chapter 5 quiz
The beaker in the illustration below contains two solutions of salt with different concentrations (measured by molarity, M). The two solutions are separated by a membrane that is permeable to both salt and water.
Diffusion of water from B to A and of salt from A to B. Instructional Guidance: Prior adequate attention to the difference between diffusion and net diffusion (or movement and net movement) of a substance across a membrane is very important if this question is used on an exam.
Some drugs are now being delivered into cells through liposomes, in which the drug is surrounded by a phospholipid bilayer. How do the drugs enter into the cell?
The liposome fuses with the phospholipid bilayer of the cell.
Amino acids with hydrophobic side chains are often found in the region of an integral membrane protein that spans the membrane.
True
What factors are required for net movement of a substance to occur by facilitated diffusion?
a concentration gradient, a plasma membrane, a transport protein
The electrical component of an electrochemical gradient is due to:
a greater concentration of positive charges on the side of the membrane with the highest concentration of protons.
Which one of the following describes the hydrophilic component of cholesterol?
a hydroxyl group only
Which one of the following is considered an integral membrane protein?
a protein with its N-terminus in the cytoplasm and its C-terminus in the extracellular space
Freeze fracture is a technique used to visualize membrane proteins. In this technique, cells are rapidly frozen and then split, separating the lipid bilayer into its two component layers. Transmembrane proteins stay associated with one layer and leave a pit in the other. The fluid mosaic model predicts what kind of pattern of proteins and pits?
a random arrangement of proteins and pits
An amphipathic molecule is one that:
contains both polar and nonpolar regions.
The random movement of molecules is referred to as:
diffusion.
A protein that is temporarily associated with a biological membrane is a(n):
peripheral membrane protein.
The lipid components of cellular membranes often include:
phospholipids and cholesterol.
Long, saturated fatty acid tails _____ lipid mobility and _____ membrane fluidity.
reduce; decrease
Which part of a cholesterol molecule is polar?
the OH group
Phospholipids spontaneously form a variety of structures in aqueous solution. This property accounts at least in part for which of the following?
All of the answer options depend on this property of phospholipids.
The plasma membranes of some plant cells use transport proteins to move protons out of the cell against their concentration gradient. This is an example of:
active transport.
A phospholipid molecule in a membrane can:
both spin (rotate around its vertical axis) and move side to side (lateral movement).
Suppose you are studying the transport of a certain polar molecule across the plasma membrane of cells in culture. Over a period of time, you measure the concentration of a polar molecule inside and outside of the cells. You find that the concentration of the molecule is lower in the cell but is gradually increasing. You also measure the ATP concentration inside the cell and find that it is not changing. Which of the following is probably responsible for the transport of this polar substance into the cell?
facilitated diffusion
Exposure of purified phospholipids to water results in the spontaneous formation of
lipid bilayers
Specific types of lipids assemble into defined areas of a biological membrane referred to as
lipid rafts
Which one of the following is NOT a component of an animal cell's plasma membrane?
nucleic acid
