Question

When a peptide hormone reaches its target cell, which event happens next? A. It binds itself to the receptors present on the surface of the cell membrane, which activates the enzymes present inside cell. B. It passes through the cell membrane and attaches itself to a receptor protein present in the cytoplasm. C. It passes on the signal to the secondary messengers inside the cell, which activate the receptors on the cell membrane.

Answer 1

Answer:

A. It binds itself to the receptors present on the surface of the cell membrane, which activates the enzymes present inside cell.

Explanation:

Peptide hormones being hydrophilic cannot cross the plamsa membrane of cell which is largely made up of phospholipids so in order to show their impact and participate in the signal transduction pathway they are bound to interact with the cell surface receptors first. Their interaction with the receptor, activates various intracellular enzymes of the cell which ultimately leads to the physiological response within the cell. GPCR is the best example of cell surface receptor to which hormones like epinephrine and nor epinephrine bind. They bind themselves to the receptors present on the surface of the cell membrane, which activate the enzymes present inside cell. In contrast to this, steroid hormones being hydrophobic can cross the cell membrane directly and attach themselves with the intracellular receptors to show their impact.

Answer 2

"It binds itself to the receptors present on the surface of the cell membrane,which activates the enzymes present inside cell" is the one event that happens next when a peptide hormone reaches its target cell. The correct option among all the options that are given in the question is the first option or option "A".