Chapter 11

Put the steps of the process of signal transduction in the order they occur:

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11) Which component is a protein fiber of the extracellular matrix?

A

Consider this pathway: epinephrine → G-protein-coupled receptor → G-protein → adenylyl cyclase → cAMP. The second messenger in this pathway is ________.

A) cAMP

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?

A) integrins

50) Which of the following statements about quorum sensing is FALSE? Quorum sensing ________.

A) is cell—cell communication in eukaryotes

One characteristic of life and living systems is that they are able to adapt. In general, cells interact with other cells and their environment through the action of their ________.

A) plasma membrane and extracellular matrix

18) In plant cells, the middle lamella ________.

Allows adjacent cells to adhere one another

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

B) Plant ECM is primarily carbohydrate in nature, whereas animal ECM is mainly proteins.

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?

B) The victim's muscles would be unable to relax.

When yeast cells of opposite mating types are in close proximity, cell changes occur inside those cells that result in the polymerization of actin filaments, allowing the yeast cells to mate. Those changes in cell behavior are initially due to signaling molecules (pheromones) released by the yeast cells. Pheromones are ________.

B) a type of hormone that binds cell-surface receptors causing cytoplasmic actin proteins to form filaments

Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because ________.

B) intracellular receptors are present only in target cells

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

B) part of the extracellular matrix

17) For a tissue or an organ to function as a unit, ________.

B) there must be cell—cell communication among the cells within a tissue or organ

22) 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 ________.

B) water ions and small molecules can readily pass from one cardiac muscle cell to the next

7) Which of the following statements is FALSE?

C) A plant cell continues growing after the secondary cell wall forms but stops growing with the formation of the tertiary cell wall.

26) Different body cells can respond differently to the same peptide hormones because

C) a target cell's response is determined by the components of its signal transduction pathways

10) All of the following proteins may be found in the extracellular matrix of animal cells EXCEPT ________.

C) actin

Protein kinase is an enzyme that ________.

C) activates or inactivates other proteins by adding a phosphate group to them

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

C) collagen

Signals from the extracellular matrix to the cytoskeleton may be transmitted by ________.

C) integrins

24) 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 ________.

D) a loss in cell—cell adhesion

Hormones are chemical substances produced in one organ that are released into the bloodstream and affect the function of a target organ. For the target organ to respond to a particular hormone, it must ________.

D) have receptors that recognize and bind the hormone molecule

The extracellular matrix is thought to participate in the regulation of animal cell behavior by communicating information from the outside to the inside of the cell via which of the following?

D) integrins

One of the major categories of receptors in the plasma membrane reacts by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this?

D) receptor tyrosine kinases

25) A cell with membrane-bound proteins that selectively bind a specific hormone is called that hormone's ________.

D) target cell

At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of estrogens and other steroid hormones. How can one hormone, such as estrogen, mediate so many effects?

Estrogen binds to specific receptors inside many kinds of cells, each with different responses.

When yeast cells of the "a" mating type are exposed to a solution of "α" pheromones ________.

G-proteins will be activated in the cell-signaling pathway and the yeast cells will change shape

15) Plasmodesmata in plant cells are most similar in function to which of the following structures in animal cells?

Gap Junctions

Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through ________.

Gap Junctions

Which observation suggested the involvement of a second messenger in epinephrine's effect on liver cells?

Glycogen breakdown was observed only when epinephrine was administered to intact cells.

A mutation that disrupts the ability of an animal cell to add polysaccharide modifications to proteins would most likely cause defects in its ________.

Golgi apparatus and extracellular matrix

19) Where would you expect to find tight junctions?

In the epithelium of an animals stomach.

43) Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because they ________.

amplify the original signal many times

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 (cell junctions), 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 that 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?

The molecules responsible for cell—cell adhesion (cell junctions) differed between the two species of sponge.

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

The physical form of the signal changes from one form to another.

The cell walls of bacteria, fungi, and plant cells and the extracellular matrix of animal cells are all external to the plasma membrane. Which of the following is a characteristic common to all of these extracellular structures?

They are constructed of polymers that are synthesized in the cytoplasm and then transported out of the cell.

What do the cell walls of plants and the extracellular matrix of animal cells have in common?

They have functional connections with the cytoskeleton inside the cell.

Not all intercellular signals require transduction. Which one of the following signals would be processed without transduction?

a lipid-soluble signal

Plasmodesmata are cell—cell junctions that are found between ________.

adjacent plant cells

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 ________.

be transported through the nuclear pore complex

Integrins are integral membrane proteins. They are often attached to ________.

cytoskeletal proteins and proteins in the extracellular matrix

Type II diabetics have normal to elevated levels of insulin. What, then, might be causing their elevated blood glucose levels?

defective receptors

The activation of receptor tyrosine kinases is characterized by ________.

dimerization and phosphorylation

Forms of the Ras protein found in tumors usually cause which of the following?

excessive cell division

In signal transduction, phosphatases ________.

inactivate protein kinases and turn off the signal transduction

Which of the following is characteristic of a steroid hormone action?

internal receptor binding

36) A G-protein receptor with GTP bound to it ________.

is in its active state

Scaffolding proteins are ________.

large molecules to which several relay proteins attach to facilitate cascade effects

48) The cancer-causing forms of the Ras protein are involved in which of the following processes?

relaying a signal from a growth-factor receptor

In general, a signal transmitted via phosphorylation of a series of proteins ________.

results in a conformational change to each protein

A gap junction is a channel that connects adjacent cells. Which one of the following cannot pass through a gap junction?

ribosomes

receptors for steroid hormones are located inside the cell instead of on the membrane surface like most other signal receptors. This is NOT a problem for steroids because ________.

steroid hormones are lipid soluble, so they can readily diffuse through the lipid bilayer of the cell membrane