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BIO 140 Human Biology I - Questions and Solutions

Hormones - Solutions

Review Questions

1. A newly developed pesticide has been observed to bind to an intracellular hormone receptor. If ingested, residue from this pesticide could disrupt levels of ________.

  1. melatonin
  2. thyroid hormone
  3. growth hormone
  4. insulin

2. A small molecule binds to a G protein, preventing its activation. What direct effect will this have on signaling that involves cAMP?

  1. The hormone will not be able to bind to the hormone receptor.
  2. Adenylyl cyclase will not be activated.
  3. Excessive quantities of cAMP will be produced.
  4. The phosphorylation cascade will be initiated.

3. A student is in a car accident, and although not hurt, immediately experiences pupil dilation, increased heart rate, and rapid breathing. What type of endocrine system stimulus did the student receive?

  1. humoral
  2. hormonal
  3. neural
  4. positive feedback


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Critical Thinking Questions

1. Compare and contrast the signaling events involved with the second messengers cAMP and IP3.

Solution: In both cAMP and IP3–calcium signaling, a hormone binds to a cell membrane hormone receptor that is coupled to a G protein. The G protein becomes activated when the hormone binds. In the case of cAMP signaling, the activated G protein activates adenylyl cyclase, which causes ATP to be converted to cAMP. This second messenger can then initiate other signaling events, such as a phosphorylation cascade. In the case of IP3–calcium signaling, the activated G protein activates phospholipase C, which cleaves a membrane phospholipid compound into DAG and IP3. IP3 causes the release of calcium, another second messenger, from intracellular stores. This causes further signaling events.

2. Describe the mechanism of hormone response resulting from the binding of a hormone with an intracellular receptor.

Solution: An intracellular hormone receptor is located within the cell. A hydrophobic hormone diffuses through the cell membrane and binds to the intracellular hormone receptor, which may be in the cytosol or in the cell nucleus. This hormone–receptor complex binds to a segment of DNA. This initiates the transcription of a target gene, the end result of which is protein assembly and the hormonal response.


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OpenStax, Hormones. OpenStax CNX. Jun 18, 2013 http://cnx.org/contents/093ae45b-1c94-42d2-868d-1e50e7895155@3. © Jun 18, 2013 OpenStax. Textbook content produced by OpenStax is licensed under a Creative Commons Attribution License 3.0 license.