Chemical signals travel to their target by

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Chemical signals travel to their target by

Chemical signals move through the surrounding fluid by diffusion, spreading from where they are released toward nearby target cells until they encounter receptors. This passive movement follows concentration gradients and requires no cellular energy. Diffusion works naturally for short-range signaling (paracrine or autocrine) because molecules simply diffuse through the extracellular fluid to reach receptors. Endocytosis and exocytosis are about vesicle transport: exocytosis releases substances from a cell, and endocytosis brings substances into a cell. Active transport moves substances across membranes against their gradients and isn’t the mechanism by which a signaling molecule travels through the extracellular space to reach receptors.

Chemical signals move through the surrounding fluid by diffusion, spreading from where they are released toward nearby target cells until they encounter receptors. This passive movement follows concentration gradients and requires no cellular energy. Diffusion works naturally for short-range signaling (paracrine or autocrine) because molecules simply diffuse through the extracellular fluid to reach receptors.

Endocytosis and exocytosis are about vesicle transport: exocytosis releases substances from a cell, and endocytosis brings substances into a cell. Active transport moves substances across membranes against their gradients and isn’t the mechanism by which a signaling molecule travels through the extracellular space to reach receptors.

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