1. Which of the following statements about collagen is false?
It is asecreted protein.
It is the mostabundant protein in animal tissues.
It forms adouble helix, with two collagen molecules wrapped around oneanother in a ropelike structure.
It contains anamino acid called hydroxyproline.
2. Which of the following is not a reason why collagenfibrils form extracellularly rather than intracellularly during thebiosynthesis and transport of collagen from the endoplasmicreticulum through the Golgi apparatus to the cell surface?
Type Iprocollagen synthesized in cells contains nonhelical segments ateach end of the polychain that limit their ability to oligomerizeinto collagen fibrils.
Type Iprocollagen cannot form the triple helical oligomers that are thecore structure of any collagen oligomer.
Type Iprocollagen contains hydroxylated proline and lysine residues thatprevent polypeptide chain oligomerization within the cell.
Procollagenmust be soluble and small enough to fit within the intracellulartransport machinery.
3. Homophilic interactions between cells involve interactions between
between integrins and ICAMs.
adhesionmolecules of the same molecular class.
cadherins andβ-catenin.
adhesionmolecules of different molecular classes.
4. The basic structural polysaccharide of fungal cell walls, crabshells, and insect exoskeletons is
chitin.
cellulose.
collagen.
hemicellulose.
5. Adherens junctions and desmosomes may be distinguished fromeach other on the basis of
the presenceof cadherins versus ICAMs.
whether thecadherins are linked directly or indirectly to the cytoskeletalelements.
the linkage ofcadherins either to actin filaments or to intermediatefilaments.
whether thelinkage is between two cells or between a cell and theextracellular environment.
6. Which of the following is not true of integrins?
Each subunithas a large extracellular head group.
It has twosubunits termed α and β that dimerizewith each other.
Each subunithas a short cytoplasmic domain that interacts with intracellularproteins such as talin, α-actinin, and plectin.
Signals fromthe extracellular matrix activate integrins to assume ahead-group-extended conformation.