What effects do paracrine signals have in cell communication?

• A. They affect nearby target cells.
• B. They are involved in direct cell-to-cell contact.
• C. They travel through the bloodstream to distant cells.
• D. They primarily affect the cell that secreted them.

Answer: (A)

Verified step by step guidance

1. Understand the concept of paracrine signaling: Paracrine signals are a form of cell communication where the signaling molecules affect nearby target cells. This is different from endocrine signaling, which involves hormones traveling through the bloodstream to distant cells.
2. Identify the characteristics of paracrine signals: Paracrine signals are typically short-lived and act locally, affecting cells in the immediate vicinity of the secreting cell.
3. Differentiate paracrine signaling from other types of signaling: Unlike autocrine signaling, which affects the cell that secreted the signal, paracrine signaling targets nearby cells. It does not involve direct cell-to-cell contact like juxtacrine signaling.
4. Consider the mechanism of action: Paracrine signals often involve the release of signaling molecules such as growth factors or cytokines into the extracellular space, where they bind to receptors on nearby cells.
5. Evaluate the options given in the problem: Based on the understanding of paracrine signaling, determine which options correctly describe its effects. Paracrine signals affect nearby target cells, not distant cells through the bloodstream, and do not primarily affect the secreting cell.