Exam 7: Membrane Structure and Function

According to the fluid mosaic model of cell membranes, phospholipids ________.

For the following questions, match the labeled component of the cell membrane in the figure with its description. - Which component in the accompanying figure plays a critical role in cell-cell recognition? A) A B) B C) C D) E

A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in ________.

In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis?

A sodium-potassium pump ________.

For the following questions, match the labeled component of the cell membrane in the figure with its description. - Which component in the accompanying figure is hydrophilic? A) A B) B C) C D) D

When a plant cell, such as one from a tulip leaf, is submerged in a hypertonic solution, what is likely to occur?

Which of the following types of molecules lack hydrophilic domains?

Which of the following statements correctly describes osmosis?

Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells? The animal cell is in ________.

Which of the following types of molecules are hydrophilic and therefore excluded from the hydrophobic portion of the phospholipid bilayer?

Use the paragraph and accompanying figure to answer the following questions. 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 labeled the lipids on the HIV membrane with a red fluorescent dye. -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 ________.

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

Use the paragraph and accompanying figure to answer the following questions. 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 labeled the lipids on the HIV membrane with a red fluorescent dye. -What would be observed by live-cell fluorescence microscopy immediately after HIV entry if HIV is endocytosed first, and then later fuses with the endocytotic vesicle membrane?

Three lab groups carried out an experiment to identify the concentration of sucrose in six solutions. Each unknown contained one of the following sucrose concentrations: 0.0 M, 0.2 M, 0.4 M, 0.6 M, 0.8 M, and 1.0 M. Cubes of sweet potato (1 cm³) were soaked for 24 hours in each solution and weighed to determine the change in mass. Each data entry represents the average of three sample replicates expressed as percent change in mass following a 24-hour soak in the unknown solutions. Based on the data provided, the intracellular molarity of dissolved solutes in sweet potato cells is approximately ________.

Which of the following statements describes a characteristic feature of a carrier protein in a plasma membrane?

The solutions in the two arms of this U-tube are separated by a membrane that is permeable to water and glucose but not to sucrose. Side A is half-filled with a solution of 2 M sucrose and 1 M glucose. Side B is half-filled with 1 M sucrose and 2 M glucose. Initially, the liquid levels on both sides are equal. In the U-tube illustrated above, ________.

Which of the following statements about diffusion is true?

The membranes of winter wheat are able to remain fluid when it is extremely cold by ________.

In which of the following environments would there be the greatest need for osmoregulation?