Exam 7: Membrane Structure and Function

Which of these are not embedded in the hydrophobic portion of the lipid bilayer at all?

Use the following information to answer the questions below. Cystic fibrosis is a genetic disease in humans in which the CFTR protein, which functions as a chloride ion channel, is missing or nonfunctional in cell membranes. -In the small airways of the lung, a thin layer of liquid is needed between the epithelial cells and the mucus layer in order for cilia to beat and move the mucus and trapped particles out of the lung. One hypothesis is that the volume of this airway surface liquid is regulated osmotically by transport of sodium and chloride ions across the epithelial cell membrane. How would the lack of a functional chloride channel in cystic fibrosis patients affect sodium ion transport and the volume of the airway surface liquid?

In most cells, there are electrochemical gradients of many ions across the plasma membrane even though there are usually only one or two electrogenic pumps present in the membrane. The gradients of the other ions are most likely accounted for by

Which of the following would increase the electrochemical potential across a membrane?

What kinds of molecules pass through a cell membrane most easily?

Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport mechanism is most probably functioning in the intestinal cells?

When biological membranes are frozen and then fractured, they tend to break along the middle of the bilayer. The best explanation for this is that

For the following questions, match the labelled component of the cell membrane in the figure with its description. -Which component is a glycolipid?

Which of the following types of molecules are the major structural components of the cell membrane?

For the following questions, match the labelled component of the cell membrane in the figure with its description. -Which component is the fibre of the extracellular matrix?

Which of the following is one of the ways that the membranes of winter wheat are able to remain fluid when it is extremely cold?

Use the following information to answer the questions below. Five dialysis bags, constructed from a semipermeable membrane that is impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed) and the percent change in mass of each bag was graphed. -Which line in the graph represents the bag with the highest initial concentration of sucrose?

An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function?

Water passes quickly through cell membranes because

Cell membranes are asymmetrical. Which of the following is the most likely explanation?

Which of the following factors would tend to increase membrane fluidity?

Nitrous oxide gas molecules diffusing across a cell's plasma membrane is an example of

The difference between pinocytosis and receptor-mediated endocytosis is that

Use the following information to answer the questions below. Human immunodeficiency virus (HIV) infects cells that have both CD4 and CCR5 cell surface molecules. The viral nucleic acid molecules are enclosed in a protein capsid, and the protein capsid is itself contained inside an envelope consisting of a lipid bilayer membrane and viral glycoproteins. One hypothesis for viral entry into cells is that binding of HIV membrane glycoproteins to CD4 and CCR5 initiates fusion of the HIV membrane with the plasma membrane, releasing the viral capsid into the cytoplasm. An alternative hypothesis is that HIV gains entry into the cell via receptor-mediated endocytosis, and membrane fusion occurs in the endocytotic vesicle. To test these alternative hypotheses for HIV entry, researchers labelled the lipids on the HIV membrane with a red fluorescent dye. -What would be observed by live-cell fluorescence microscopy if HIV is endocytosed first, and then fuses with the endocytotic vesicle membrane?

Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a 0.15 M salt solution become limp and soft. From this we can deduce that the cells of the celery stalks are