Question

Epidermal growth factor is a signaling molecule that travels through the blood and binds to EGF receptor proteins on target cells. This can activate a signaling pathway known as the MAP kinase pathway. This is an example of_____

a. endocrine signaling.
b. paracrine signaling.
c. autocrine signaling.
d. signaling by plasma-membrane-attached proteins.
e. All of the answers are correct.

Answer 1

The binding of epidermal growth factor (EGF) to its receptor (EGFR) on target cells, activating the MAP kinase pathway for cellular division and growth, is an example of paracrine signaling, although it can also be involved in uncontrolled cell growth if activated inappropriately.

Step-by-step explanation:

Epidermal growth factor (EGF) binding to its receptor, EGF receptor (EGFR), is an example of paracrine signaling. Paracrine signaling involves signaling molecules that affect neighboring cells. Since EGF is mentioned as traveling through the blood to bind to target cells, it suggests that it acts over a distance but within the same tissue, which aligns more with paracrine than endocrine signaling, the latter of which involves hormones that travel longer distances through the circulation system to target distant cells. Additionally, EGF binding to EGFR is known to activate the MAP kinase pathway, leading to cell division and growth, which is critical for functions like wound healing and tissue repair. However, inappropriate activation of EGFR can result in uncontrolled cell growth, which is often associated with cancer.