Exam 8: Cell Membranes

Which of the following cellular processes includes all of the others?

In some cells, there are many different ion electrochemical gradients across the plasma membrane even though there are usually only one or two types of proton pumps present in the membrane. The gradients of the other ions are most likely established by which of the following?

Which component in the figure above represents a protein fiber of the extracellular matrix?

The force driving simple diffusion is ________, while the energy source for active transport is ________.

Which of the following processes is used by white blood cells when engulfing bacteria?

Which of the following statements best describes a characteristic feature of osmosis?

Which of the following results is most likely result if a portion of an animal's blood is replaced with distilled water?

A new drug designed for the treatment of lung cancer must specifically enter the cytoplasm of lung cells while not entering the cells of other tissues. Which of the following characteristics would likely enhance the specificity of this drug?

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 enters the cell by endocytosis first, and then later fuses with the endocytotic vesicle membrane?

Which of the following statements best explains how the membranes in winter wheat are able to remain fluid in extremely cold temperatures?

Three lab groups carried out an experiment to identify the concentration of sucrose in six solutions. Each unknown solution (1-6) 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. Which unknown solution contains the highest concentration of sucrose?

Which of the following molecules would likely diffuse through the lipid bilayer of a plasma membrane most rapidly?

Which of the following statements best describes a characteristic of biological membranes?

Which component in the figure above is hydrophilic?

Which of the following statements most accurately compares primary factors responsible for simple diffusion versus active transport?

Which of the following statements best describes a characteristic feature of diffusion?

The phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. Because phosphate import depends on a pH gradient across the membrane, phosphate transport is most likely an example of which of the following transport processes?

Three lab groups carried out an experiment to identify the concentration of sucrose in six solutions. Each unknown solution (1-6) 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. From the data provided, which unknown solution has a molarity that most closely reflects the molarity of sweet potato cells?

The voltage across a membrane is called the ________.

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly ________.