Exam 5: Cell Membrane Structure and Function

Which of the following is an energy-requiring mode of transport that brings substances into a cell?

When a mouse cell and a human cell are fused, the membrane proteins of the two cells become uniformly distributed over the surface of the hybrid cell. This occurs because

The cytoplasm of a certain cell, such as a neuron, already has a high concentration of K ⁺ ions. How can K⁺ ions continue to enter the cell?

In reference to diffusion, passive really means

The bacterium Vibrio cholerae releases a toxin that blocks a channel protein in the membranes of cells that line the intestine. This toxin prevents the movement of sodium ions from the inside of the intestine into cells. If the sodium ions could not move into the cells, how would this affect the movement of water between the inside of the intestine and the cells?

What would happen if the plasma membrane were composed solely of phospholipids and no proteins?

Osmosis is the diffusion of water molecules across selectively permeable membranes.

The antibiotic polymyxin B attaches itself to the phospholipids in the phospholipid bilayer and increases the permeability of the membrane. Describe what will occur as a result.

Protein channels that provide passage for hormones and nutrients between animal cells are termed

Solutions that cause water to enter cells by osmosis are called

Suppose that plasma membranes were single layers of phospholipids rather than double layers, and the heads faced the extracellular fluid. The interior of this hypothetical cell would have to be

Facilitated diffusion and active transport both require__________for the movement of molecules across the membrane.

According to the fluid mosaic model of cell membranes, which of the following is a TRUE statement about membrane phospholipids?

The rate of facilitated diffusion of a molecule across a membrane will increase as the concentration gradient of the molecule across the membrane increases to a certain point. Eventually, an increase in the concentration of the molecule will not cause any further increase in facilitated diffusion. Thus, there is a maximal rate of facilitated diffusion. This is because

Carbon dioxide crosses the plasma membrane by simple diffusion. The rate at which carbon dioxide enters the cell is determined by the

Which of the following would NOT be found in a membrane?

The main lipids found in cell membranes are

For diffusion to occur, there must be

Cystic fibrosis is a genetic disease that leads to the production of excessive, thick mucus in the respiratory tract, causing frequent and serious respiratory infections. The defect is due to the production of a faulty membrane protein for the transport of the chloride ion. The protein exists in membranes, but it doesnʹt function normally. Based on this scenario, what is occurring at the molecular level in a person with cystic fibrosis?

Communication between cells occurs via __________in plant cells and via__________ in animal cells.