bio chapter 8

What role do plasmodesmata play in plant cells? They prevent the plant cell from losing water in desert conditions. They serve as communication portals between neighboring plant cells, allowing the passage of substances between the two cells. They allow the plant cell to withstand extreme temperatures. They serve as sites of protein production in the cell.

They serve as communication portals between neighboring plant cells, allowing the passage of substances between the two cells.

The most abundant protein found in the extracellular matrix of animal cells is _____. pectin collagen hemoglobin cellulose

collagen

Why does a hormone only act on specific cell types in an organism and not others? Hormones only act on cells that are adjacent to the releasing cell. Hormones are prevented from entering the bloodstream, and thus only act on the releasing cell itself. All cells will take up the hormone and process it, but not all cells will elicit a response. A cell must have the appropriate receptor before it can bind to the hormone.

A cell must have the appropriate receptor before it can bind to the hormone.

Which statement best describes what would happen if you treated cells in a developing frog embryo with a molecule that blocked a cadherin observed in muscle tissue? Adhesion of muscle cells to other muscle cells would be disrupted. The formation of the middle lamella between adjacent muscle cells would be disrupted. Adhesion of muscle cells to cells of non-muscle tissues would be disrupted. Connections between the cytoskeleton of muscle cells and the ECM would be disrupted.

Adhesion of muscle cells to other muscle cells would be disrupted.

Why is it important for signal transduction systems to trigger a rapid response within a cell and be able to be shut down quickly? All signal transduction cascades are shut down immediately so as to prevent the cell from mounting a response. Cells are unable to respond quickly to hormones, and therefore signal transduction cascades always occur over a long time. Cells often have to respond very quickly to changes in their internal and external environments. Cells have to be able to function alone, because they are unable to work together in a coordinated fashion.

Cells often have to respond very quickly to changes in their internal and external environments.

Which statement best explains why the existence of multiple steps in a signal transduction pathway allows it to be regulated by several other pathways? Multiple steps allow the signal to be amplified. Multiple steps provide a series of points where hormone can bind. Multiple steps convert the signal from one form to another. Multiple steps provide a series of points where cross-talk can occur.

Multiple steps provide a series of points where cross-talk can occur.

How is phosphorylation important in a signal transduction cascade? Phosphorylation will shut down a signal transduction cascade, thus leading to an end of the signal. When the hormone itself becomes phosphorylated, it travels to all nearby cells and activates them to release more hormones of that same type. Phosphorylation will turn an inactive protein into an active one, which triggers another response in the cell. A hormone will phosphorylate the entire cell, thus causing the cell to be marked for destruction.

Phosphorylation will turn an inactive protein into an active one, which triggers another response in the cell.

Which statement is correct concerning how the molecular composition of a plant cell wall compares with the ECM of animal cells? The fibers in a plant cell wall are proteins; ECM fibers are dominated by carbohydrates. Plant cell walls exhibit fundamentally different design principles than ECM. Plant cell wall fibers consist of carbohydrates; ECM fibers are dominated by proteins. In the plant cell wall, the ground substance surrounding the fibers contains carbohydrates; in the ECM it does not.

Plant cell wall fibers consist of carbohydrates; ECM fibers are dominated by proteins.

Which of the following statements most accurately describes the function of plasmodesmata in plant cells or gap junctions in animal cells? Plasmodesmata allow passage of only proteins between adjacent cells. Gap junctions allow passage of proteins and small molecules between adjacent cells. Gap junctions allow passage of only proteins between adjacent cells. Plasmodesmata allow passage of proteins and small molecules between adjacent cells.

Plasmodesmata allow passage of proteins and small molecules between adjacent cells.

Which statement most accurately explains how some signals are amplified? Enzymes remove phosphate groups from proteins. Receptors are blocked. More hormone is produced. Second messengers are produced.

Second messengers are produced.

Which statement most accurately predicts what would happen to animal cells if they are treated with an enzyme that cuts integrin molecules? The adhesion of the cells to adjacent cells would be weakened. The cytoskeleton of the cells would fall apart. The ECM surrounding the cells would dissolve. The cell wall surrounding the cells would dissolve.

The adhesion of the cells to adjacent cells would be weakened.

How can a hormone that is present in very small quantities within the bloodstream elicit such a large response within a cell? The hormone is only taken up by the largest cells in the body, and thus it can elicit a large response. The hormone is always an extra large macromolecule even though it is present in minute quantities. Cells degrade the hormone into many tiny molecules, and then each piece creates a response within the cell. The message from the hormone is amplified many times within the cell.

The message from the hormone is amplified many times within the cell.

The long and complex series of events that occurs when a signal binds to the cell surface and is converted from one form to another is called _____. action potential transesterification reaction signal cross-wiring signal transduction

signal transduction

The type of cell-cell attachment that resembles quilting, with proteins acting as stitches, is _____. tight junctions selective adhesions desmosomes gap junctions

tight junctions