Chapter 19

Which of the following cell junctions uses cadherin cell adhesion molecules to anchor the actin cytoskeleton via catenins? A. Adherens junction B. Tight junction C. Desmosome D. Add to dictionary E. Gap junction

A. Adherens junction

Which collagens are the most common in our body? A. Fibrillar B. Fibril-associated C. Network-forming D. Proteoglycan core E. Anchorage fibril

A. Fibrillar

Desmosomes and hemidesmosomes are anchored to which component(s) of the cytoskeleton? A. Intermediate filaments B. Actin and microtubules C. Microtubules D. Actin belts

A. Intermediate filaments

Cell junctions that prevent small molecules from passing in between two other cells are called A. Tight junction B. Gap junctions C. Adhesions D. Plasmodesmata E. All of the above

A. Tight junction

Which of the following is NOT an anchoring junction? A. Tight junction B. Adherens junction C. Desmosome D. Actin-linked cell-matrix junction E. Hemidesmosome

A. Tight junction

Which of the following cell junctions uses cadherin cell adhesion molecules to anchor the actin cytoskeleton? A. Tight junction B. Adherens junction C. Desmosome D. Hemidesmosome E. Gap junction

B. Adherens junction

Which of the following junctions is most abundant in tissues such as skin that are required to resist significant mechanical stress? A. Gap junctions B. Desmosomes C. Focal adhesions D. Tight junctions E. All are abundant in tissues resisting stress

B. Desmosomes

Which components of the extracellular matrix are mostly responsible for its ability to resist compressive and tensile forces, respectively? A. Collagens and glycoproteins B. Glycosaminoglycan and collagens C. Glycoproteins and collagens D. Glycosaminoglycan and glycoproteins E. Collagens and glycosaminoglycans

B. Glycosaminoglycan and collagens

For cadherins in general, binding A. Is heterophilic B. Is homophilic C. Depends on the Sn+ concentration D. Requires matrix metalloproteases

B. Is homophilic

Collagens are extremely rich in ... A. alanine and valine. B. glycine and proline. C. lysine and arginine. D. serine and threonine. E. tyrosine and phenylalanine.

B. glycine and proline.

This large glycoprotein of the extracellular matrix is associated with elastin fibers and is essential for their integrity. Its deposition in the developing connective tissues often precedes the appearance of elastin. It is part of microfibrils that cover the elastic fibers. This protein is ... A. Collagen. B. Fibronectin. C. Fibrillin. D. Filamin. E. Laminin.

C. Fibrillin.

Type IV collagen molecules can interact at their C-termini to form dimers and at their N-termini to form tetramers. What category do you think this type of collagen belongs to? A. Fibrillar B. Fibril-associated C. Network-forming D. Proteoglycan core E. Anchorage fibril

C. Network-forming

Animal extracellular matrices contain each of the following except A. Collagens B. Proteoglycans C. Pectins D. Fibronectins E. Elastins

C. Pectins

Plasmodesmata in plant cells are functionally similar to animal cells' ... A. adherens junctions. B. desmosomes. C. gap junctions. D. hemidesmosomes. E. tight junctions.

C. gap junctions.

Indicate whether each of the following descriptions better applies to connective (C) or epithelial (E) tissues. Your answer would be a four-letter string composed of letters C and E only, e.g. EEEE. ( ) Cells are usually distributed sparsely in the extracellular matrix. ( ) Gap junctions are rarely found. ( ) Direct cell-cell attachments are common. ( ) Cells are tightly associated into sheets.

CCEE

Consider two cells attached to each other via adherens junctions. The forces generated by the actin cytoskeleton in one cell... A. Are dependent on myosin activity B. Are normally balanced by similar forces in the neighboring cell C. Can strengthen the adherens junction by unfolding catenin proteins D. All of the above

D. All of the above

Which of the following molecules is capable of tension-sensing by exposing binding sites for other proteins when mechanically stretched? A. α-Catenin B. Talin C. Fibronectin D. All of the above

D. All of the above

Consider two cells attached to each other via adherens junctions. The forces generated by the actin cytoskeleton in one cell ... A. are dependent on myosin activity. B. are normally balanced by similar forces in the neighboring cell. C. can strengthen the adherens junction by unfolding catenin proteins. D. All of the above.

D. All of the above.

Selectins... A. Mainly mediate cell-matrix attachments B. Are members of the Ig superfamily of cell adhesion molecules C. do NOT require Ca2+ for their adhesive function, unlike integrins. D. Are carbohydrate-binding proteins E. All of the above

D. Are carbohydrate-binding proteins

Which components of the extracellular matrix are mostly responsible for its ability to resist compressive and tensile forces, respectively? A. Collagens and glycoproteins B. Glycoproteins and collagens C. Glycosaminoglycans and glycoproteins D. Glycosaminoglycans and collagens E. Collagens and glycosaminoglycans

D. Glycosaminoglycans and collagens

In insects such as Drosophila melanogaster, electrical synapses are abundant in the ventral nerve cord. Unlike a chemical synapse, the cytosols of pre- and postsynaptic cells in an electrical synapse are connected, allowing action potentials to spread rapidly and without delay. What junctional proteins in the flies are chiefly responsible for this unique feature of the electrical synapses? A. Cadherins B. Claudins C. Connexins D. Innexins E. Integrins

D. Innexins

Gap junctions ______ A. Couple cells metabolically, but not electrically B. Are formed from monomeric hemichannels C. Are made of innexins in humans D. None of the above are correct

D. None of the above are correct

Which of the following extracellular matrix components contains a transmembrane protein? A. Type I collagen B. Perlecan C. Aggrecan D. Syndecan E. Decorin

D. Syndecan

Selectins ... A. mainly mediate cell-matrix attachments. B. are members of the Ig superfamily of cell adhesion molecules. C. do NOT require Ca2+ for their adhesive function, unlike integrins. D. are carbohydrate-binding proteins. E. All of the above.

D. are carbohydrate-binding proteins.

Overproduction of cadherins such as E-cadherin ... A. is often found in cancers originating from epithelia. B. is induced by the transcription regulatory protein Twist. C. induces epithelial-mesenchymal transition. D. leads to stronger cell-cell adhesion. E. All of the above.

D. leads to stronger cell-cell adhesion.

Fill in the blank in the following paragraph. Do not use abbreviations. "Particularly abundant in cells of heart muscle and the epidermis, ... are structurally similar to adherens junctions and contain a number of homologous components. However, their cadherin molecules are linked to intermediate filaments instead of the actin cytoskeleton."

Desmosomes

How is hyaluronic acid different from other glycosaminoglycans of the extracellular matrix? A. It lacks sulfate groups B. It is generally not covalently linked to proteins C. It is not assembled in the Golgi apparatus D. It can be several megadaltons in mass E. All of the above

E. All of the above

Slug, Snail, and Twist are important factors in which of the following processes? A. Epithelial to mesenchymal transition (EMT) B. Cancer C. Cell migration D. Altered expression of cadherins E. All of the above

E. All of the above

How is hyaluronic acid different from other glycosaminoglycans of the extracellular matrix? A. It lacks sulfate groups. B. It is generally not covalently linked to proteins. C. It is not assembled in the Golgi apparatus. D. It can be several megadaltons in mass. E. All of the above.

E. All of the above.

Polarized cells are characterized by A. Random orientation within a tissue B. Being surrounded on all sides by a basement membrane C. Junctions only to ECM and not to other cells D. Formation of several connected layers of cells E. Distinct apical and basolateral ends of the cell

E. Distinct apical and basolateral ends of the cell

Which of the following is NOT an anchoring junction? A. Adherens junction B. Desmosome C. Actin-linked cell-matrix junction D. Hemidesmosome E. Tight junction

E. Tight junction

Indicate true (T) and false (F) statements below regarding integrin signaling. Your answer would be a four-letter string composed of letters T and F only, e.g. TFTT. ( ) Integrins usually bind their ligands with a higher affinity compared to other cell-surface receptors. ( ) Unlike cadherins, integrins usually function as individual dimers and do not cluster. ( ) Anchorage dependence is mainly mediated via integrin signaling. ( ) Integrins can activate the Ras-MAPK pathway.

FFTF

Indicate true (T) and false (F) statements below regarding cadherins. Your answer would be a four-letter string composed of letters T and F only, e.g. TFTT. ( ) Cadherins are present in all multicellular organisms. ( ) Adhesion by cadherins is dependent on Ca2+ ions. ( ) In contrast to nonclassical cadherins, classical cadherins are more closely related in sequence. ( ) E, N, and P cadherins are mainly found in desmosomes.

FTTF

Indicate true (T) and false (F) statements below regarding glycosaminoglycan chains in the extracellular matrix. Your answer would be a four-letter string composed of letters T and F only, e.g. TFTT. ( ) They are highly branched polysaccharides. ( ) They are strongly hydrophilic and absorb a large amount of water. ( ) They all contain N-acetylglucosamine or N-acetylgalactosamine. ( ) They are highly positively charged.

FTTF

Indicate true (T) and false (F) statements below regarding the interaction of cells with the extracellular matrix using matrix receptors. Your answer would be a four-letter string composed of letters T and F only, e.g. TFTT. ( ) Integrins are the only known matrix receptors in animal cells. ( ) Integrins can transmit signals in both directions across the membrane; that is, both outside-in and inside-out. ( ) Tension can increase the binding affinity of an integrin for its intracellular and extracellular ligands. ( ) Integrins can convert molecular signals into mechanical ones.

FTTT

Fill in the blank in the following paragraph regarding the extracellular matrix. Do not use abbreviations. "The extracellular matrix of connective tissues in animals is primarily made and secreted by the ... family of cells, although they may have more specific names in certain tissues. Being common in connective tissues, these cells can also migrate and proliferate if need be."

Fibroblasts

Indicate whether each of the following descriptions better applies to glycosaminoglycans (G), fibrous proteins (F), or glycoproteins (P) of the extracellular matrix in animal cells. Your answer would be a six-letter string composed of letters G, F, and P only, e.g. GFPGFP. ( ) They include laminin and fibronectin. ( ) They primarily include collagens. ( ) They include hyaluronan. ( ) They are found in proteoglycans. ( ) They occupy large volumes and form hydrated gels. ( ) They constitute the major proteins of the matrix.

PFGGGF

Indicate whether each of the following descriptions better applies to adherens junctions (A), desmosomes (D), gap junctions (G), or tight junctions (T). Your answer would be a four-letter string composed of letters A, D, G, and T only, e.g. AAAD. ( ) They play a direct role in structural polarization of epithelial cells. ( ) They couple cells both electrically and metabolically. ( ) They are formed from hexameric hemichannels that can assemble into heterotypic complexes. ( ) They create semipermeable paracellular pores.

TGGT