Chapter 9
Notch and Delta are both transmembrane proteins involved in cell communication in the developing nervous system of vertebrate animals. What makes Notch different from Delta?
Notch is a receptor, and Delta is a signaling molecule.
Many scientists use chemical inhibitors to interfere with normal signaling pathways within eukaryotic cells. If such inhibitors are large nonpolar molecules, what is the likely method of action of these chemical inhibitors?
These chemical inhibitors likely bind to receptors on the cell surface and interfere with receptor activation or signal-receptor binding.
Normal heart cells beat more strongly when they are exposed to adrenaline. When adrenaline is removed, normal heart cells return to their normal beat strength within a few minutes. One type of mutant heart cell has lost the function of one part of the signaling process. They respond abnormally by continuing to beat strongly for hours after a single brief exposure to adrenaline. Which step in the adrenaline signaling pathway is most likely to be disrupted in the mutant cells?
The enzymes that cause termination of the response
Why don’t steroid hormones bind to transmembrane cell-surface receptors?
Steroid hormones are nonpolar and therefore are able to cross the cell’s cell membrane, binding to receptors inside the cell.
Which is a true statement about receptors that are localized to the nucleus?
They carry a nuclear-localization signal.
They bind nonpolar ligands.
They move through a nuclear pore.
They are synthesized in the cytosol.
All of these choices are correct.
How does an “activated” receptor transfer information into the cell?
Through a conformational change in the cytoplasmic domain of the receptor
Signaling molecules involved in paracrine and autocrine signaling:
Travel by diffusion
Most ligands form covalent bonds with their associated receptors; these complexes are more or less permanent and can only be broken through the hydrolysis of ATP.
False
Which components of cell signaling are involved in only some types of cell communication?
Signal transduction molecules
In cell communication, which of these is a requirement of the responding cell?
It must express receptor proteins
A cell can only respond to signals from other cells, not from the physical environment.
False
Which is the correct order for these steps in cell signaling?
Receptor activation, signal transduction, response
Growth factors such as platelet-derived growth factor (PDGF) function in:
Paracrine signaling
A cell that responds to an environmental condition by the release of a chemical is an example of which element of cellular communication?
A signaling cell
Chapter 27
Childbirth in mammals is an example of endocrine-controlled negative feedback because the production of oxytocin during childbirth results in additional oxytocin being synthesized by the posterior pituitary gland.
False
Receptors for _____ hormones are located on the plasma membrane and affect target cells by _____.
Amine; activating protein kinase enzymes
An individual who is experiencing a prolonged period of stress would likely have _____ levels of circulating _____ than an individual who is not experiencing stress.
Higher; cortisol
Which statement is false?
The effects of paracrine signals are more immediate but longer-lasting than the effects of hormones.
In Rhodnius, the amount of juvenile hormone _____, and the level of ecdysone _____ over time until later nymphal stages (4th molt) occur.
Decreases; stays the same
The two main classes of hormones are:
Amine/peptide hormones and steroid hormones.
Jet-lagged travelers are often advised to take _____ to restore their normal circadian rhythms.
Melatonin
Which statement is not a correct pairing?
Fibroblast growth factor (FGF): bone formation
