#Question id: 1373
#Unit 4. Cell Communication and Cell Signaling
Following statements are regarding to cholera toxins which can affect the junction’s activity.
a. Toxins produced by Vibrio cholerae, the enteric bacterium that causes cholera, alter the permeability barrier of the intestinal epithelium by altering the composition or activity of gap junctions.
b. Vibrio cholerae also releases a protease that disrupts tight junctions by degrading the extracellular domain of occludin.
c. Toxin-induced changes in tight-junction permeability (increased paracellular transport) and in protein-mediated ion pumping (decreased transcellular transport) can result in massive losses of internal body ions and water into the gastrointestinal tract, which in turn leads to diarrhea and potentially lethal dehydration.
d. Toxin-induced changes in tight-junction permeability (decreased paracellular transport) and in protein-mediated ion pumping (increased transcellular transport) can result in massive losses of internal body ions and water into the gastrointestinal tract, which in turn leads to diarrhea and potentially lethal dehydration.
Which of the following statements are correct?
#Question id: 1374
#Unit 4. Cell Communication and Cell Signaling
Following statements are regarding to gap junctions.
i. Vertebrate gap junctions are composed of connexins, a family of structurally related transmembrane proteins with molecular weights between 26,000 and 60,000.
ii. Each vertebrate hexagonal particle consists of six noncovalently associated connexin molecules. Each individual connexin molecule has two membrane-spanning α helices with a topology similar to that of claudin.
iii. The permeability of gap junctions is regulated by posttranslational modification of connexins (e.g., phosphorylation) and is sensitive to changes in environmental conditions
such as intracellular pH and Ca2+ concentration, membrane potential, and the intercellular potential between adjacent interconnected cells (“voltage gating”).
iv. The assembly of connexins, their trafficking within cells, and the formation of functional gap junctions apparently depend on N-cadherin and its associated adapter proteins as well as desmosomal proteins.
Which of the following statements are correct?
#Question id: 1375
#Unit 4. Cell Communication and Cell Signaling
Four ECM ubiquitous protein components, each of which comprises multiple, distinct, repeating domains, are found in basal laminae. Given below are a list of some extracellular matrix (ECM) proteins in column A and their characteristics in column B.
|
Column A |
Column B |
|
a. Type IV collagen |
i. a large multidomain proteoglycan that binds to and cross-links many ECM components and cell-surface molecules. |
|
b. Laminins |
ii. a rodlike molecule that cross-links type IV collagen, perlecan, and laminin, which helps incorporate other components into the ECM and also stabilizes basal laminae. |
|
c. Perlecan |
iii. a family of multi-adhesive, cross-shaped proteins that form a fibrous two-dimensional network with type IV collagen and that also bind to integrins and other adhesion receptors. |
|
d. Nidogen |
iv. trimeric molecules with both rodlike and globular domains that form a two-dimensional network. |
Which one of the following is the most appropriate match?
#Question id: 1376
#Unit 4. Cell Communication and Cell Signaling
Which of the following statements is NOT TRUE about gap junctions?
#Question id: 1377
#Unit 4. Cell Communication and Cell Signaling
Which of the following statements apply to both eukaryotic cell walls and animal cell extracellular matrices? Please select all that apply.
a) They are inflexible structures that support cells.
b) They are built to a common overall structure that can be described as 'fibres in a matrix'.
c) Their protein components are synthesized by ribosomes of the rough endoplasmic reticulum.
d) They limit the diffusion of ions and small molecules into the cell.
#Question id: 1378
#Unit 4. Cell Communication and Cell Signaling
Which of the following apply to fibronectins? Please select all that apply.
a) They are disulphide linked dimers, with each polypeptide composed of a number of binding domains joined together by short flexible segments.
b) They have an essential role in linking the extracellular matrix to its underlying cells.
c) Like integrins, fibronectins are directly connected to the cytoskeleton.
d) They participate in 'inside out' and 'outside in' signalling mechanisms.