How does cyclic AMP (cAMP) function as a second messenger?

How does cyclic AMP (cAMP) function as a second messenger?

• A. By binding directly to DNA
• B. By activating protein kinase A (PKA)
• C. By degrading phospholipids
• D. By inhibiting protein synthesis

Answer: (B)

Cyclic AMP (cAMP) functions as a second messenger primarily by activating protein kinase A (PKA). When a signaling molecule, such as a hormone or neurotransmitter, binds to a G protein-coupled receptor (GPCR) on the cell surface, it can lead to the activation of adenylate cyclase. This enzyme catalyzes the conversion of ATP to cAMP. The increase in cAMP concentration in the cell then activates PKA. Once activated, PKA phosphorylates specific target proteins, which can lead to various cellular responses, such as changes in metabolism, gene expression, or cellular growth and differentiation. This signaling cascade illustrates the role of cAMP in transmitting external signals into the cell, effectively amplifying the initial signal and leading to a coherent cellular response. The other choices describe processes that do not accurately represent the role of cAMP. For example, cAMP does not bind directly to DNA or degrade phospholipids. Additionally, while it can influence processes that may indirectly affect protein synthesis, cAMP itself does not directly inhibit protein synthesis. Thus, the activation of PKA is the defining characteristic of cAMP's role as a second messenger.

Cyclic AMP (cAMP) functions as a second messenger primarily by activating protein kinase A (PKA). When a signaling molecule, such as a hormone or neurotransmitter, binds to a G protein-coupled receptor (GPCR) on the cell surface, it can lead to the activation of adenylate cyclase. This enzyme catalyzes the conversion of ATP to cAMP. The increase in cAMP concentration in the cell then activates PKA.

Once activated, PKA phosphorylates specific target proteins, which can lead to various cellular responses, such as changes in metabolism, gene expression, or cellular growth and differentiation. This signaling cascade illustrates the role of cAMP in transmitting external signals into the cell, effectively amplifying the initial signal and leading to a coherent cellular response.

The other choices describe processes that do not accurately represent the role of cAMP. For example, cAMP does not bind directly to DNA or degrade phospholipids. Additionally, while it can influence processes that may indirectly affect protein synthesis, cAMP itself does not directly inhibit protein synthesis. Thus, the activation of PKA is the defining characteristic of cAMP's role as a second messenger.