Exam 8: Cell-Cell Interactions

Of the following,where would you expect to find tight junctions?

What is a major difference between the extracellular matrix (ECM)of a plant cell and the ECM of an animal cell?

H.V.Wilson worked with sponges to gain some insight into exactly what was responsible for holding adjacent cells together.He exposed two species of differently pigmented sponges to a chemical that disrupted the cell-cell interaction,and the cells of the sponges dissociated.Wilson then mixed the cells of the two species and removed the chemical that caused the cells to dissociate.Wilson found the sponges reassembled into two separate species.The cells from one species did not interact or form associations with the cells of the other species.How do you explain the results of Wilson's experiments?

Scientists have found that extracellular matrix components may induce specific gene expression in embryonic tissues such as the liver and testes.For this to happen there must be direct communication between the extracellular matrix and the developing cells.Which kind of transmembrane protein would most likely be involved in this kind of induction?

Steroid hormones bind to receptors inside the cell and alter their conformation.The hormone-receptor complex is then transported into the nucleus,where it can directly affect gene expression.To get from the location where the receptor binds the hormone to its site of action,the hormone-receptor complex must _____.

Acetylcholine is a neurotransmitter that binds to receptors on skeletal muscle cells.The receptor-signal complex brings about a series of events that result in contraction of skeletal muscle.Venom from black widow spiders causes an explosive release of acetylcholine.What would that do to its victims?

Protein kinase is an enzyme that _____.

Osteocytes are bone cells.Collagen fibers and calcium salts are found in abundance between and among the osteocytes.The collagen and calcium salts are _____.

For a tissue or an organ to function as a unit,_____.

One characteristic of life and living systems is that they are able to adapt.Toward this end,cells interact with other cells and their environment through the action of their _____.

Plasmodesmata are cell-cell junctions that are found between _____.

Intercalated discs are cell-cell junctions found between cardiac muscle cells.One feature of these intercalated discs is that they contain a large number of gap junctions,which means that _____.

Put the steps of the process of signal transduction in the order they occur: 1)A conformational change in the signal-receptor complex activates an enzyme. 2)Protein kinases are activated. 3)A signal molecule binds to a receptor. 4)Target proteins are phosphorylated. 5)Second messenger molecules are released.

Blood sugar is regulated by two pancreatic hormones,insulin and glucagon.When blood sugar rises,insulin is released;it binds to receptors and,through signal transduction,results in an increase in glucose uptake by cells,which effectively lowers blood glucose levels.When blood sugar decreases,glucagon is released,binds to cell receptors,and causes glucose to be released into circulation,thereby increasing blood glucose levels.Diabetes mellitus is a disorder that results from excessively high levels of blood glucose.Type II diabetics have normal to elevated levels of insulin.What,then,might be causing their elevated blood glucose levels?

All of the following proteins may be found in the extracellular matrix of animal cells except _____.

A G-protein receptor with GTP bound to it _____.

Which of the following would you not find in a plant cell?

A gap junction is a channel that connects adjacent cells.From substances listed,which one cannot pass through a gap junction?

Pemphigus vulgaris is an autoimmune disorder in humans in which antibodies are produced against the cadherins of desmosomes.The blistering of the skin and mucous membranes characteristic of this disorder is probably a result of _____.

What does it mean to say that a signal is transduced?