Chapter 11 Homework
Why does a hormone act only on specific cell types in an organism and not others?
A cell must have the appropriate receptor before it can bind to the hormone.
How does the absence of a signal transduction cascade in the processing of steroid hormones affect the cellular response that is possible?
As with a signal transduction pathway, gene expression may be altered. Other types of responses, such as muscle contraction or the rapid mobilization of glucose, are not possible.
_____ aid in the coordination of the activities of adjacent animal cells.
Gap (communicating) junctions. Gap junctions allow for the passage of material between cells, thus facilitating communication between these cells.
How does the absence of a signal transduction cascade in the processing of steroid hormones affect signal amplification?
No amplification can occur because the number of signaling molecules dictates the size of the response.
How does the absence of a signal transduction cascade in the processing of steroid hormones affect signal regulation?
Only one step is available for regulation, which includes either blocking the receptor or making it more responsive to the signaling molecule.
How is phosphorylation important in a signal transduction cascade?
Phosphorylation will change the activity of target proteins, which triggers another response in the cell.
Which statement most accurately explains how some signals are amplified?
Second messengers are produced.
How can a hormone that is present in very small quantities within the bloodstream elicit such a large response within a cell?
The message from the hormone is amplified many times within the cell.
How do only certain cells respond to particular signaling molecules that may be sent throughout the body?
They express the appropriate receptor.
What characteristics do desmosomes bestow on tissues that use these adhesions to connect adjacent cells?
They provide strong connections to resist pulling forces.
What role do plasmodesmata play in plant cells?
They serve as communication portals between neighboring plant cells, allowing the passage of small molecules between the two cells.
The primary role of _____ is to bind animal cells together.
desmosomes. The primary role of desmosomes (anchoring junctions) is to bind cells together.
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 _____.
signal transduction
Which of these cell junctions form a barrier to the passage of materials?
tight junctions, Tight junctions form a barrier that prevents fluids from moving between cells.