Exam 7: Cell Membranes, Transport, and Communication

In the flowchart below summarizing membrane transport, both active and facilitated transports terminate at separate carrier proteins; explain why the lines do not converge at the same carrier protein.

The principle of cell ____________________ is that different cells in the same organism may have different functions.

A given signaling molecule can bind to several different kinds of cell surface receptors.

Active carrier proteins use energy to carry passive carrier proteins into cells.

Several types of lipoproteins exist; the best balance for cardiovascular health is achieved with ____________________ LDL and ____________________ HDL.

Gap junctions allow large molecules to move from cell to cell.

Cells that experience high mechanical stress, like heart cells, typically connect to one another using a(n)____________________ junction, allowing the stress to be distributed to a larger area.

Cell surface receptors of chemical messages are made of

Active transport

Water moves across a membrane from a hypotonic solution to a ____________________ solution.

Channel proteins require energy for transporting molecules across the plasma membrane.

Lipids often move within the body in complexes known as lipoproteins; what advantage does this strategy provide?

Signaling molecules can be "tagged" by attaching glow-in-the-dark molecules to them. After adding tagged signaling molecules to the fluid around several cells, you observe the cells with a microscope designed to see glow-in-the-dark molecules. After a few minutes, you notice that the plasma membrane of some of the cells begins to glow. This observation indicates that some cells

Which of the following could not easily diffuse across a plasma membrane?

Animal cells are attached to neighboring cells by

Plants have hormones.

The arrows in the figure below show the movement of water across the cell wall and plasma membrane of a plant cell. For water to move in the direction indicated, the solution surrounding the cell must be

Passive carrier proteins

All steroid hormones are hydrophobic. Where would you expect the receptor proteins for these hormones to be located?

All movement, including that of diffusing molecules, requires a small expenditure of energy; what is the source of the energy that makes diffusion across the cell membrane possible?