Question Set #8

Zona occludens are formed at ____ junctions and desmosomes are formed at ____ junctions

1. cell - cell 2. cell - matrix

A calcium - dependent cell adhesion molecule found at desmosomes is:

Cadherin

Each of the following statements about cadherins is true EXCEPT: A. adhesion is Ca 2+ - dependent and homophilic B. Cadherins interact with components of the basement membrane C. Cadherins associate with the actin cytoskeleton D. When mixed together, cells expressing different cadherins sort out into homotypic cell aggregates

Cadherins interact with components of the basement membrane

Which of the following is not associated with cell - cell adhesions? A. Collagen B. Desmosome C. Gap junction D. Tight junction

Collagen

T/F: Cadherins are cell - surface carbohydrate - binding proteins that mediate transient, Ca 2+ dependent cell - cell adhesion in the bloodstream, for example between white blood cells and endothelial cells

False!

T/F: The immunoglobulin superfamily of proteins are calcium dependent cell adhesion molecules found at desmosomes

False!

T/F: The immunoglobulin superfamily of proteins are calcium - dependent cell adhesion molecules found at desmosomes

False! * Ca 2+ independent

T/F: Besides the plasma membranes of the cells, adherens junctions are primarily responsible for the function of the columnar epithelium as a permeability barrier.

False!!

Action potential propagation in cardiac cells is important for the proper function of the heart. Which of the following intracellular connections will be most effective in cardiac cells? A. Gap junctions - they facilitate exchange of fluid between cells B. Gap junctions - they facilitate exchange of ions between cells C. Tight junctions - they facilitate exchange of ions between cells D. Tight junctions - they facilitate exchange of fluid between cells

Gap junctions - they facilitate exchange of ions between cells

Integrin binding to I- CAM (IgSF member) is best categorized as an example of which of the following adhesion? A. Homophilic B. Lectin - carbohydrate C. Heterophilic D. Junctional

Heterophilic

A patient is found to have a defect in his intermediate filaments. Which of the following cellular junctions will be absent in this patient? I. Desmosomes II. Gap junctions III. Hemidesmosomes

I and III

Which of the following are true of the integrins? A. each member of the family recognizes only a single ECM protein B. All integrins are involved in the cell - ECM adhesion C. Integrin binding of ECM can stimulate cell - signaling pathways that regulate cell growth, survival and gene expression D. Integrins are a major component of the zonula adheres junctions

Integrin binding of ECM can stimulate cell - signaling pathways that regulate cell growth, survival and gene expression

Which of the following processes is required in order for neutrophil rolling to occur in response to inflammatory signals? A. recognition of endothelial cell fibronectin by interns on the neutrophil surface B. Integrin dependent binding of the neutrophil to I -CAM under flow conditions C. Arrest and extravasation of the neutrophil under flow conditions D. P - selection dependent binding of neutrophil to the endothelium under flow conditions

P - selection dependent binding of the neutrophil to the endothelium under flow conditions

Member of a family of cell - surface carbohydrate - binding proteins that mediate transient, Ca 2+ dependent cell - cell adhesion in the bloodstream, for example between white blood cells and the endothelium of the blood vessel wall.

Selectins

Which statement BEST describes tight junctions? A. The main function of the tight junction is for cell - to - cell communication B. The main function of the tight junction is for cell - to - cell adhesion C. The main function of the tight junction is to provide an occluding barrier to free movement of materials across an epithelium D. Tight junctions tether epithelial cells underlying basement membrane

The main function of the tight junction is to provide an occluding barrier to free movement of materials across an epithelium

A researcher is analyzing an autoimmune disease. The results indicated that the patient has antibodies targeting occluding proteins. What is likely to be true for the patient?

There is an easy passage of molecules through the space between adjacent cells

Which of the following statements about desmosomes is true? A. They are the portion of the junctional complex that is closest to the lumen B. They function as a diffusion barrier C. They are associated with intermediate filaments D. Connexin membrane proteins contribute to their structure

They are associated with intermediate filaments

Tight junctions have which of the following characteristics? A. They function in intracellular communication B. They function as a permeability barrier C. They anchor cells to the basal lamina D. They give strength to the epidermis of the skin so that it can resist abrasion

They function as a permeability barrier

Desmosomes provide structural integrity to tissues that undergo severe mechanical stress. What characteristics of these junctional structures provides the mechanical stability that many tissues require?

They link intermediate filaments of the cytoskeleton in one cell to those in another cell

Which of the following statements about tight junctions is correct: A. They allow for intracellular communication B. They maintain the distinct composition of plasma membrane domains C. They are associated with cadherin molecules D. They bind to proteins in the basal lamina

They maintain the distinct composition of plasma membrane domains

A researcher notices a connection between two cells. Upon analyzes, he concludes that there is no exchange of water or ions between cells. Which could be the identity of the connections between the two cells ?

Tight junction

Monocytes (precursors of neutrophils) are attracted to a site on inflammation. The directed motion is accomplished by the expression of selectins expressed by the monocytes and the endothelial cells lining the blood vessel. Once at the site of damage, the monocyte leaves the blood vessel and enters the tissues (extravasation). Which of the following cell junctions would block best the movement of the monocyte from the vessel into the tissue? A. Adherens junctions B. Hemidesmosomes C. Gap junctions D. Tight junctions

Tight junctions

The association of actin filaments with which of the following junctions gives mechanical stability to the apical end of the columnar epithelial cells?

adherens junctions (zonulae adherens)

Which of the following is true for desmosomes and hemidesmosomes? A. The cell adhesion molecule integrin is used in both junctions B. Both are made of the same cytoskeletal filaments C. Desmosomes are cell matrix junctions, whereas, hemidesmosomes are cell - cell junctions D. only desmosomes are found in epithelial cells

both are made of the same cytoskeletal filaments

Each of the following is true of both cadherins and integrins EXCEPT: A. both are transmembrane glycoproteins B. both can associate with the actin cytoskeleton C. both may be found in zonula adherens junctions D. both may represent gene families

both may be found in zonula adherens junctions

Focal adhesions are dynamic structures that contain integrins attached to the cytoskeleton and the ECM protein fibronectin. What functions are attributed to the dynamic nature of focal adhesions?

cell migration (locomotion)

Malignant melanoma cells arise from melanocytes, pigment producing cells that normally reside in the basal layer of the epidermis (skin). Progression to highly invasive metastatic cancer involves a number of steps that involve changes in cell adhesion. Which of the following changes are most likely to precede the initial release of a melanoma cell from the epidermis?

decreased cell - cell adhesion and decreased adhesion to the basement membrane

Type of anchoring junction that links intermediate filaments in two adjoining cells

desmosome

Which cellular junctions mediate direct attachment of the cytoskeletons between adjacent cells?

desmosomes

Which of the following cell surface specializations involves both cadherin membrane proteins and intermediate filaments? A. Desmosomes B. Focal contacts (focal adhesions) C. Hemidesmosomes D. Tight Junctions

desmosomes

Which type of cell junction would be adversely affected by a disorder resulting in functionally defective integrins?

focal adhesions

Some extracellular matrix (ECM) molecules are able to function in cell - cell adhesion by acting as an "intermediate linker" between cells. Which of the following statements is most likely to be a common feature of any individual ECM molecule capable of linking adjacent cells to one another?

has multiple binding sites for cell - surface adhesion molecules

A defect in which of the following types of junctions is likely to result in an epithelium that is no longer tightly adherent to the basement membrane? A. Gap junction B. Tight junction C. Adherens junction D. Hemidesmosome

hemidesmosome

Which of the following classes of junctions would be adversely affected in a disease that reduced integrin gene expression in an epithelium?

hemidesmosomes

Which of the following types of adhesion best describes cadherin function at sites of cell -cell contact? A. homophilic adhesion B. lecithin binding to carbohydrate C. heterophilic adhesion D. hemidesmosome binding to the basement membrane

hemophiliac adhesion

In the ECM, fibronectin is a ligand of a particular adhesion molecule. Therefore, that adhesion molecule most likely belongs to which family?

integrins

The key components of desmosomes are cadherins and ____ ?

intermediate filaments

In patients with leukocyte adhesion deficiency (LAD), which of the following cells are conspicuously absent from sites of infection? A. mast cells B. neutrophils C. plasma cells D. eosinophils

neutrophils

What is the main function of a tight junction?

restricts paracellular transport, segregates plasma membrane proteins in domains (e.g. apical, basolateral)

What property is unique to cell adhesion mediated by selectins?

selectins on one cell bind to the glycosylated ligands on another cell

Cell adhesion to the ECM glycoprotein fibronectin can involve:

the binding of integrins to the Arg- Gly- Asp (RGD) sequence in fibronectin

Which of the following is NOT a property of integrins? A. they are transmembrane proteins B. they exist in the membrane as homodimers C. they bind to extracellular matrix glycoproteins D. they are mechanically linked to the actin cytoskeleton

they exist in the membrane as homodimers

Besides the plasma membrane of its cells, which one of the following features of columnar epithelium is primarily responsible for its function as a permeability barrier?

tight junctions (zonula occludens)

Peptides containing the sequence RGD (arginine - glycine - aspartic acid) would be expected to interfere with all of the following functions EXCEPT: A. platelet aggregation B. adhesion of cells to extracellular matrix C. fibroblast movement D. tissue - specific cell sorting

tissue - specific cell sorting