Cyclic AMP

Definition

Cyclic AMP (cAMP) is a secondary messenger molecule that plays a crucial role in various cellular signaling pathways, particularly in the context of gene regulation. It is derived from adenosine triphosphate (ATP) and acts as an intracellular signal transducer, mediating the effects of extracellular signals such as hormones and neurotransmitters.

5 Must Know Facts For Your Next Test

1. Cyclic AMP is synthesized from ATP by the enzyme adenylyl cyclase, which is activated by specific extracellular signals.
2. Cyclic AMP acts as a second messenger, relaying the effects of hormones and neurotransmitters to the cell's interior.
3. The primary effector of cAMP is Protein Kinase A (PKA), which phosphorylates various target proteins, leading to changes in their activity and cellular processes.
4. In the context of gene regulation, cAMP-PKA signaling can influence the expression of genes by modulating the activity of transcription factors.
5. Cyclic AMP plays a crucial role in the regulation of the lac operon, a well-studied example of gene regulation in bacteria.

Review Questions

• Explain the role of cyclic AMP in the regulation of the lac operon in bacteria.
  • In the lac operon, cyclic AMP (cAMP) acts as a positive regulator of gene expression. When glucose is scarce, cAMP levels rise, and the cAMP-CRP (cAMP receptor protein) complex binds to the lac promoter, enhancing the transcription of the lac genes. This allows the bacteria to utilize lactose as an alternative carbon source. The cAMP-CRP complex helps recruit RNA polymerase to the lac promoter, increasing the expression of the lac operon genes and enabling the bacteria to metabolize lactose more efficiently.
• Describe the mechanism by which cyclic AMP mediates cellular signaling and influences gene expression.
  • Cyclic AMP (cAMP) is a secondary messenger that transduces extracellular signals, such as hormones and neurotransmitters, into intracellular responses. When an extracellular signal activates a G protein-coupled receptor, it stimulates the enzyme adenylyl cyclase to convert ATP into cAMP. Increased cAMP levels then activate the enzyme Protein Kinase A (PKA), which phosphorylates various target proteins, including transcription factors. These phosphorylated transcription factors can then bind to specific DNA sequences, either activating or repressing the transcription of target genes, thereby influencing gene expression and cellular processes.
• Analyze the importance of the cAMP-PKA signaling pathway in the context of gene regulation and cellular homeostasis.
  • The cAMP-PKA signaling pathway is crucial for maintaining cellular homeostasis and regulating gene expression in response to various extracellular stimuli. By acting as a second messenger, cAMP amplifies and transmits the effects of hormones and neurotransmitters, allowing the cell to quickly adapt to changes in its environment. The activation of PKA by cAMP leads to the phosphorylation of transcription factors, which can then modulate the expression of genes involved in metabolism, cell growth, and other essential cellular processes. Dysregulation of the cAMP-PKA pathway has been implicated in various diseases, highlighting its importance in maintaining proper cellular function and overall organismal health.

Related terms

Adenylyl Cyclase: The enzyme responsible for the synthesis of cAMP from ATP, activated by specific extracellular signals.

Protein Kinase A (PKA): A key effector of cAMP that phosphorylates various target proteins, leading to changes in their activity and cellular processes.

Operon: A genetic regulatory system in bacteria and some prokaryotes where a group of genes are transcribed and regulated together as a single unit.