In signal transduction pathways, water soluble hormones often
A bind to a receptor in the plasma membrane that activates CAMP.
B bind to a receptor in the plasma membrane that activates a protein.
C pass through the plasma membrane and bind with a G protein.
D pass through the plasma membrane and bind with CAMP.
The correct answer and explanation is :
The correct answer is A: bind to a receptor in the plasma membrane that activates cAMP.
Explanation:
Signal transduction pathways involve a series of steps that allow cells to respond to external signals, such as hormones. These pathways are essential for regulating various physiological processes in the body, such as metabolism, growth, and immune responses. Water-soluble hormones, such as peptide hormones (e.g., insulin, glucagon, and adrenaline), cannot directly cross the cell membrane due to their hydrophilic nature. Instead, they rely on receptors located on the plasma membrane to relay their signals into the cell.
When a water-soluble hormone binds to its receptor on the plasma membrane, it typically activates a cascade of intracellular signaling events. One common mechanism for signal transduction involves the production of cyclic AMP (cAMP), a secondary messenger. The binding of the hormone to the receptor activates an enzyme called adenylate cyclase, which converts ATP into cAMP.
Once cAMP is produced, it activates protein kinase A (PKA), an enzyme that can then phosphorylate various target proteins within the cell. This phosphorylation can lead to various cellular responses, such as changes in gene expression, metabolism, or cellular function.
Thus, the key feature of water-soluble hormones in signal transduction is their use of a receptor on the plasma membrane, which activates intracellular signaling pathways involving secondary messengers like cAMP. This mechanism contrasts with fat-soluble hormones (e.g., steroid hormones), which can pass through the plasma membrane and bind to intracellular receptors, often influencing gene transcription directly.
In summary, Option A is correct because water-soluble hormones bind to plasma membrane receptors, leading to the activation of cAMP, which in turn activates protein kinases and initiates a cascade of cellular events.