Which of the following is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal?
A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose
Which of the following would increase the electrochemical potential across a membrane?
a proton pump
The sodium-potassium pump in animal cells requires cytoplasmic ATP to pump ions across the plasma membrane. When the proteins of the pump are first synthesized in the rough ER, what side of the ER membrane will the ATP binding site be on?
It will be on the cytoplasmic side of the ER.
Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya. What does this most probably mean?
Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life.
Several epidemic microbial diseases of earlier centuries incurred high death rates because they resulted in severe dehydration due to vomiting and diarrhea. Today they are usually not fatal because we have developed which of the following?
hydrating drinks that include high concentrations of salts and glucose
Familial hypercholesterolemia is characterized by which of the following?
defective LDL receptors on the cell membranes
The difference between pinocytosis and receptor-mediated endocytosis is that
pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity.
In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis?
on the inside surface of the vesicle
A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in
After the system reaches equilibrium, what changes are observed?
The water level is higher in side A than in side B.
If you examine side A after three days, you should find
a decrease in the concentration of NaCl and a decrease in the water level
Which line in the graph represents the bag that contained a solution isotonic to the 0.6 M solution at the beginning of the experiment?
Which line or lines in the graph represent(s) bags that contain a solution that is hypertonic at 50 minutes?
What would be observed by live-cell fluorescence microscopy if the red fluorescent lipid dye-labeled HIV membrane fuses with the target cell plasma membrane?
The red fluorescent dye-labeled lipids will diffuse in the infected cell's plasma membrane and become difficult to detect
What would be observed by live-cell fluorescence microscopy if HIV is endocytosed first, and then fuses with the endocytotic vesicle membrane?
A spot of red fluorescence will move into the infected cell's interior.
Using live-cell fluorescence microscopy, researchers observed that a red fluorescent spot moved from the plasma membrane into the interior of target cells when red fluorescent dye-labeled HIV was added to the cells. What is the best conclusion from these observations?
The hypothesis that HIV enters the cell via fusion with the target cell plasma membrane is not supported.
If HIV first enters the cell in an endocytotic vesicle, instead of directly fusing with the plasma membrane, then
HIV infection should be hindered by microtubule polymerization inhibitors such as nocodazole.
In an HIV-infected cell producing HIV virus particles, the viral glycoprotein is expressed on the plasma membrane. How do the viral glycoproteins get to the plasma membrane?
They are synthesized by ribosomes in the rough ER, and arrive at the plasma membrane in the membrane of secretory vesicles.
If the sodium ion concentration outside the cell increases, and the CFTR channel is open, in what direction will chloride ions and water move across the cell membrane?
Both chloride ions and water will move out of the cell.
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?
Sodium ion transport will decrease; lower osmotic potential will decrease airway surface liquid volume.
A patient has had a serious accident and lost a lot of blood. In an attempt to replenish body fluids, distilled water-equal to the volume of blood lost-is transferred directly into one of his veins. What will be the most probable result of this transfusion?
The patient's red blood cells will swell because the blood fluid has become hypotonic compared to the cells.
You are working on a team that is designing a new drug. In order for this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule selectively enters the target cells?
similarity of the drug molecule to other molecules transported by the target cells
In what way do the membranes of a eukaryotic cell vary?
Certain proteins are unique to each membrane.
According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly
embedded in a lipid bilayer
Which of the following factors would tend to increase membrane fluidity?
a greater proportion of unsaturated phospholipids