The Biology Project > Cell Biology > Cell Signaling > Problem Set

Cell Signaling Problem Set

Problem 1: Receptors

Tutorial to help you answer the question

A protein receptor binds a hormone outside the cell membrane and activates a protein kinase inside the cell. Is the receptor a peripheral or integral membrane protein?


Membrane receptors are peripheral, or associated with the surface of the bilayer. Association with a hormone results in the release of a lipid signal that activates protein kinases.


Membrane receptors associated with signaling are all integral membrane proteins that can transmit signals through the lipid bilayer.


Membrane receptors

Membrane receptors generally function by binding the signal, or ligand and causing the production of a second signal (second messenger) that causes a cellular response. The diagram shows how the receptor for insulin functions.

A pair of insulin molecules bind to receptors, causing a change in the protein structure that exposes a kinase or phosphate transferring enzyme inside the cell.

The activated receptor kinase transfers a phosphate group to adjacent receptor molecules, leading to the activation of subcellular proteins and a cellular response to insulin.

The receptors must be integral membrane proteins that pass through the lipid bilayer. Through this system, an insulin molecule can cause a response inside the cell without passing through the lipid bilayer.

Membrane receptors

Answer | Problem 2

The Biology Project > Cell Biology > Cell Signaling > Problem Set

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May 2002
Revised: August 2004
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