Download Answers to Biological Inquiry Questions – Brooker et al ARIS site

Answers to Biological Inquiry Questions – Brooker et al ARIS site
Chapter 52
Figure 52.14
BIOLOGICAL INQUIRY QUESTION: How might it be possible for a single molecule to exert different
effects on cells at different concentrations?
ANSWER: Different concentrations of a signaling protein can exert different effects on cells when, for
example, different cells express different isoforms of a plasma membrane receptor for the protein. If
one cell expresses a high-affinity receptor and another cell a low-affinity receptor, the two cells would
respond to the signaling protein at different concentrations. Likewise, the different receptors may be
linked with different second messenger molecules generated within the cell. These messengers,
such as cAMP and Ca2+, may have different effects on cell function.
Figure 52.17
BIOLOGICAL INQUIRY QUESTION: Are there other examples in animals in which one protein binds
another to prevent its action?
ANSWER: Yes, and such activity occurs not only during development but at all stages of life. For
example, certain proteins secreted into the blood of adult mammals can bind signaling proteins such
as hormones, thereby sequestering them and preventing their actions.