Exam 16: Cell Walls, the Extracellular Matrix, and Cell Interactions

Responsible for much of the rigidity of plant tissues, _______ is the internal hydrostatic pressure that builds up within the cell and equalizes its osmotic pressure.

The major protein of the extracellular matrix of animal cells is

Tight junctions provide strong adhesions between cells.

What is the primary function of tight junctions?

Tight junctions involve a fusion between the outer leaflets of two membranes in the region of the junction.

Integrins are homodimers of two transmembrane polypeptide subunits.

Desmosomes are linked to cytoplasmic

Integrins are dimeric transmembrane proteins of the plasma membrane. According to the fluid mosaic model of membrane structure (see Chapter 14), transmembrane proteins should be free to diffuse within the lipid bilayer. Yet, as shown by Tamkun and colleagues in 1986, integrins have a very restricted distribution in the plasma membrane of fibroblasts. The distribution often appears as a series of tracks across the cell surface. How can this distribution be explained?

A major function of tight junctions is to

Unlike polysaccharides such as glycogen or cellulose, glycosaminoglycans (GAGs) are highly negatively charged. What is the source and function of this negative charge?

Charcot-Marie-Tooth disease is a tight junction disease.

Suppose you have treated plant cells in culture with a drug to disrupt microtubules. You then examine the orientation of cellulose fibrils in newly-synthesized primary cell walls that developed under these conditions. What will be the observed orientation of the cellulose fibrils with respect to one another?

A standard approach to detaching tissue culture cells from substratum is to incubate the culture briefly in a saline solution containing a divalent cation chelator and trypsin. How does this procedure detach the cells from the surface?

Animal cells are embedded in a(n)

The cell-cell interactions mediated by the selectins, integrins, and most members of the Ig superfamily are _______ interactions in which the cytoskeletons of adjacent cells are not linked to one another.

Plasmodesmata can open and close in response to signals.

Although structurally different from gap junctions in animal cell tissues, _______ may be thought of as the functional equivalent of gap junctions in plants.

Integrin was first localized to sites of cell adhesion to the extracellular matrix by immunofluorescence microscopy.

The cell walls of bacteria are made of a copolymer of

Collagen fibrils form extracellularly and not intracellularly, even though their components are synthesized within the cell and transported to the cell surface via the Golgi. Which statement explains why this happens?