Post Lecture Quiz 3 Flashcards
The solutions in the arms of a U-tube are separated at the bottom of the tube by a selectively permeable membrane. The membrane is permeable to sodium chloride but not to glucose. Side A is filled with a solution of 0.4 M glucose and 0.5 M sodium chloride (NaCl), and side B is filled with a solution containing 0.8 M glucose and 0.4 M sodium chloride. Initially, the volume in both arms is the same. Refer to the figure to answer the following question.
If you examine side A after three days, you should find
1)
a decrease in the concentration of NaCl and a decrease in the water level.
2)
no net change in the system.
3)
a decrease in the concentration of NaCl , an increase in water level, and no change in the concentration of glucose.
4)
no change in the concentration of NaCl and glucose and an increase in the water level.
5) a decrease in the concentration of NaCl and glucose and an increase in the water level.
a decrease in the concentration of NaCl and a decrease in the water level.
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?
1)
similarity of the drug molecule to other molecules transported by the target cells
2)
lipid composition of the target cells’ plasma membrane
3)
lack of charge on the drug molecule
4)
blood or tissue type of the patient
5)
hydrophobicity of the drug molecule
1)
similarity of the drug molecule to other molecules transported by the target cells
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?
A
B
C
D
E
Particular receptor tyrosine kinases (RTKs) that promote excessive cell division are found at high levels on various cancer cells. A protein, Herceptin, has been found to bind to an RTK known as HER2. HER2 is sometimes excessive in cancer cells. This information can now be utilized in breast cancer treatment if which of the following is true?
1)
If the patient has RTKs only in cancer cells.
2)
If the patient’s cancer cells have excessive levels of HER2.
3)
If HER2, administered by injection, causes cell division.
4)
If the patient’s genome codes for the HER2 receptor.
5)
If Herceptin is found in the breast lymph nodes of the patient.
If the patient’s cancer cells have excessive levels of HER2.
Protein kinases are enzymes that catalyze phosphorylation of target proteins at specific sites, whereas protein phosphatases catalyze removal of phosphate(s) from phosphorylated proteins. Phosphorylation and dephosphorylation can function as an on-off switch for a protein’s activity, most likely through
1)
a change in the optimal temperature at which a reaction will occur.
2)
the excision of one or more peptides.
3)
a change in the optimal pH at which a reaction will occur.
4)
the change in a protein’s charge leading to cleavage.
5)
the change in a protein’s charge leading to a conformational change.
When a plant cell, such as one from a peony stem, is submerged in a very hypotonic solution, what is likely to occur?
1)
The cell will burst.
2)
Plasmolysis will shrink the interior.
3)
The cell membrane will lyse.
4)
The cell will become flaccid.
5)
The cell will become turgid.
5)
The cell will become turgid.
Which of the following is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal?
1)
The cotransporter can also transport potassium ions.
2)
A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose.
3)
Sodium ions can move down their electrochemical gradient through the cotransporter whether or not glucose is present outside the cell.
4)
Glucose entering the cell down its concentration gradient provides energy for uptake of sodium ions against the electrochemical gradient.
5)
Sodium and glucose compete for the same binding site in the cotransporter.
A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose.
Which of the following is characterized by a cell releasing a signal molecule into the environment, followed by a number of cells in the immediate vicinity responding?
1)
autocrine signaling
2)
endocrine signaling
3)
hormonal signaling
4)
synaptic signaling
5)
paracrine signaling
5)
paracrine signaling
Which of the following best describes the structure of a biological membrane?
1)
a mixture of covalently linked phospholipids and proteins that determines which solutes can cross the membrane and which cannot
2)
two layers of phospholipids with proteins either crossing the layers or on the surface of the
layers
3)
two layers of phospholipids (with opposite orientations of the phospholipids in each layer) with each layer covered on the outside with carbohydrates
4)
a fluid structure in which phospholipids and proteins flip freely between sides of the membrane
5)
two layers of phospholipids with proteins floating between the two layers
two layers of phospholipids with proteins either crossing the layers or on the surface of the
layers
An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function?
1)
cell-cell recognition
2)
maintaining fluidity of the phospholipid bilayer
3)
transporting ions against an electrochemical gradient
4)
attaching to the cytoskeleton
5)
establishing the diffusion barrier to charged molecules
cell-cell recognition
