Exam 11: Membrane Structure

Cholesterol can either make membranes more rigid or more fluid.Explain how this is possible.

In the photosynthetic archaean Halobacterium halobium, a membrane transport protein called bacteriorhodopsin captures energy from sunlight and uses it to pump protons out of the cell.The resulting proton gradient serves as an energy store that can later be tapped to generate ATP.Which statement best describes how bacteriorhodopsin operates?

Which of the following substances is most commonly used to help purify a membrane protein?

Which of the following statements about the carbohydrate coating of the cell surface is FALSE?

Consider the apical location of a particular protein expressed in epithelial cells, illustrated in part A of Figure 11-35.Which type of defect described below is the most likely to cause the redistribution of that protein around the entire cell, shown in part B of Figure 11-35 Figure 11-35

Water molecules readily form hydrogen bonds with other polar molecules, and when they encounter nonpolar molecules they must form hydrogen-bonding networks with neighboring water molecules.Which of the following molecules will cause a "cage" of water to form?

For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below.Not all words or phrases will be used; each word or phrase should be used only once. amphipathic hydrophobic phosphatidylserine cholesterol lipid bilayer phospholipids fatty acid tails lipid monolayer proteins glycolipids lipids sterols hydrophilic head groups phosphatidylcholine sugars The specialized functions of different membranes are largely determined by the __________ they contain.Membrane lipids are __________ molecules, composed of a hydrophilic portion and a hydrophobic portion.All cell membranes have the same __________ structure, with the __________ of the phospholipids facing into the interior of the membrane and the __________ on the outside.The most common lipids in most cell membranes are the __________.The head group of a glycolipid is composed of __________.

Where does most new membrane synthesis take place in a eukaryotic cell?

Both glycoproteins and proteoglycans contribute to the carbohydrate layer on the surface of the cell.Which of the following statements about glycoproteins is FALSE?

Plasma membranes are extremely thin and fragile, requiring an extensive support network of fibrous proteins.This network is called the

Which of the following membrane lipids does not contain a fatty acid tail?

Explain the reasons why membrane proteins are more difficult to isolate and purify for in vitro studies compared to cytosolic proteins.

Which of the following phospholipid precursors is the most hydrophobic?

A group of membrane proteins can be extracted from membranes only by using detergents.All the proteins in this group have a similar amino acid sequence at their C-terminus: -KKKKKXXC (where K stands for lysine, X stands for any amino acid, and C stands for cysteine).This sequence is essential for their attachment to the membrane.What is the most likely way in which the C-terminal sequence attaches these proteins to the membrane?

Sodium dodecyl sulfate (SDS) and Triton X-100 are both detergents that can be used to lyse cells to study individual components.Your first project as a Ph.D.student is to create an in vitro model that allows you to study the mechanism of action of a novel glucose transporter protein.You use SDS to lyse the cells.Later experiments demonstrate that the transporter is not functional.Provide a possible explanation for what happened, propose a solution for your next experiment, and articulate the reasons you think the new method will be more successful.