Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

16. The Endocrine System

Membrane Bound Receptors and Secondary Messengers

Anatomy & Physiology

16. The Endocrine System

Membrane Bound Receptors and Secondary Messengers

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Problem 22

Textbook Question

A researcher observes that stimulation by a particular hormone induces a marked increase in the activity of G proteins in the target plasma membrane. The hormone being studied is probably:
(a) A steroid
(b) A peptide
(c) Testosterone
(d) Estrogen
(e) Aldosterone

Verified step by step guidance

Step 1: Understand the role of G proteins in cell signaling. G proteins are intracellular signaling molecules that are activated by receptors on the plasma membrane. These receptors are typically associated with peptide or protein hormones, not steroid hormones.

Step 2: Recall the mechanism of action for steroid hormones. Steroid hormones, such as testosterone, estrogen, and aldosterone, are lipid-soluble and can pass through the plasma membrane. They typically bind to intracellular receptors rather than activating G proteins on the plasma membrane.

Step 3: Consider the mechanism of action for peptide hormones. Peptide hormones are water-soluble and cannot pass through the plasma membrane. Instead, they bind to membrane-bound receptors, which often activate G proteins as part of their signaling pathway.

Step 4: Eliminate options based on the information provided. Since G protein activation is observed, steroid hormones (testosterone, estrogen, aldosterone) are unlikely candidates because they do not typically use G protein-mediated signaling. This leaves peptide hormones as the probable answer.

Step 5: Conclude that the hormone being studied is most likely a peptide hormone, as peptide hormones are known to induce G protein activity in the target plasma membrane.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

G Proteins

G proteins are molecular switches that play a crucial role in transmitting signals from outside the cell to its interior. When a hormone binds to a receptor on the cell surface, it activates G proteins, which then trigger various intracellular signaling pathways. Understanding their function is essential for interpreting how hormones influence cellular activity.

Hormone Types

Hormones can be classified into two main types: steroid hormones and peptide hormones. Steroid hormones, such as testosterone and estrogen, are lipid-soluble and can pass through cell membranes, while peptide hormones, like many growth factors, are water-soluble and bind to receptors on the cell surface. This distinction is vital for understanding how different hormones interact with G proteins.

Signal Transduction

Signal transduction refers to the process by which a cell responds to external signals, such as hormones, through a series of molecular events. This often involves the activation of G proteins and other signaling molecules, leading to a physiological response. Recognizing the mechanisms of signal transduction is key to determining the effects of the hormone in the research scenario.