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Cell Membranes Problem Set

Problem 13: Cell junctions

Tutorial to help answer the question

The cell junctions respectively that exclude the passage of water between cells, maintain tissue form and strength, and allow the exchange of small molecules between cells are:
A. gap junctions, desmosomes, and tight junctions.
B. desmosomes, tight junctions and gap junctions.
C. tight junctions, gap junctions, and tight junctions.
D. gap junctions, tight junctions, and desmosomes.
E. tight junctions, desmosomes, and gap junctions.


Cell junctions

Graphic of junctions in animal cells

Tight junctions
Tight junctions block the flow of fluids between epithelial cells.

For example, the cells that line the intestine are responsible for taking up nutrients from the gut. The nature of the material taken up must be controlled to block unwanted substances from entering our bodies. The control comes from the fact that materials must pass through receptors on the epithelial cell membranes.

Tight junctions form a water tight seal and prevent material from passing between cells.

Tight Junctions
Desmosomes form links between cells, and provide a connection between intermediate filaments of the cell cytoskeletons of adjacent cells. This structure gives strength to tissues.
Gap junctions
Finally, the need for signaling is a function of gap junctions that form pores connecting adjacent cells. Small molecules and electrical signals in one cell can pass through the gap junctions to adjacent cells. This process allows tissues to coordinate responses to stimuli. For example, gap junctions permit coordinated movements of muscles leading to childbirth.
Gap junctions

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