Which statement is most accurate concerning how the molecular composition of a plant cell wall compares with the ECM of animal cells?
Plant cell wall fibers consist primarily of carbohydrates; ECM fibers are dominated by proteins.
Because cell walls consist of a cross-linked network of long filaments embedded in a stiff surrounding material, they can be called _____.
The most abundant protein found in the extracellular matrix of animal cells is _____.
Which statement best describes what would happen if you treated cells in a developing frog embryo with a molecule that blocked a cadherin present in muscle tissue?
Adhesion of muscle cells to other muscle cells would be disrupted.
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 proteins and small molecules between adjacent cells.
The type of cell–cell attachment that resembles quilting, with proteins acting as stitches, is _____
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.
Which statement most accurately explains how some signals are amplified?
Second messengers are produced.
Based on what you have learned about how cells ensure that proteins end up in the right place (Chapter 7), what type of signal would you expect to be exposed on a cytosolic receptor after a steroid hormone changes the receptor's conformation?
Amino acids required for transport through the nuclear pore complex
How do only certain cells respond to particular signaling molecules that may be sent throughout the body?
They express the appropriate receptor.
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.
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 _____.
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 is phosphorylation important in a signal transduction cascade?
Phosphorylation will change the activity of target proteins, which triggers another response in the cell.
A common GTP-binding molecule that links the receipt of an extracellular signal to the production of an intracellular one is _____.
a G protein
Why is it important for signal transduction systems to trigger a rapid response within a cell and be able to be shut down quickly?
Cells often have to respond very quickly to changes in their internal and external environments.
Which statement most accurately predicts what would happen to animal cells if they were treated with an enzyme that cuts integrin molecules?
The adhesion of the cells to adjacent cells would be weakened.
Adrenalin is a hormone that binds to a receptor in the plasma membrane. Which statement best explains how adrenalin can stimulate cells in both the heart and the liver, yet trigger different responses (increasing heart rate versus releasing glucose)?
Both tissues have adrenalin receptors but signal transduction activates different target proteins in the heart versus the liver
What characteristics do tight junctions bestow on tissues that use these adhesions to connect adjacent cells?
They form a watertight barrier between the cells.
What does it mean to say that a signal is amplified?
Even a single molecule evokes a large response.
In animals, where are most components of the extracellular material synthesized?
the rough ER
What would be the impact on the structure of a plant tissue if the cells lacked the ability to modify the extracellular environment?
Cells would not be able to adhere to one another.
No defined tissues, consisting of similar cells with coordinated activities, would be possible.
Cells would swell and burst if placed in a hypotonic environment.
Compare and contrast the structure and function of tight junctions, desmosomes, and gap junctions. What do they have in common?
All three are made up of membrane-spanning proteins that directly interact between adjacent cells.
Which of the following statements represents a fundamental difference between the fibers found in the extracellular layers of plants and those of animals?
Animal fibers consist of proteins; plant fibers consist of polysaccharides instead.
Treating dissociated cells with certain antibodies makes the cells unable to reaggregate. Why?
The antibodies bind to cell adhesion proteins.
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