Chapter 11Cell Communication

Single Transduction Pathway

• The process in which a signal on a cells surface is converted into a specific cellular response through a series of steps

Communicating Short Distances

• Local regulator: transmitting cell secretes these that influence cells in the vicinity– Growth factors• Stimulate nearby target cells to grow and multiply

– Panacrine signaling

– Neurotransmitters• Specific nerve cells are so close together, a signal can

travel great distances without affecting the wrong parts

• Direct contact

Communicating Long Distances

• Hormones (endocrine signaling) – Specialized cells release hormone molecules into

vessels of the circulatory system how they travel to their target cells

Three Stages of Cell Signaling

1. Reception– Target cell’s detection of a signal from outside the cell– It is detected when it binds to a cellular protein at the

cell’s surface2. Transduction– Binding of signal molecule initiates the process– Converts signal to a form that can bring about a

response3. Response– Transduced signal triggers a specific cellular response

Reception

• Signal molecule behaves as a ligand– Binding generally causes a receptor protein to

undergo a change in shape– Shape change directly activates the receptor so

that it can interact with another cellular molecule• Most receptors are membrane proteins– G-Protein-linked receptor– Tyrosine-kinase receptors– Ion-channel receptors

G-Protein-Linked Receptors

• Plasma membrane receptor that works with help of G protein

• Vary in their binding sites for recognizing signal molecules and for recognizing different G proteins inside the cell

• G protein functions as a switch 1. Receptor is activated2. Causes a protein change3. Binds to another protein and alters its activity4. Triggers the next step in the pathway

Tyrosine-Kinase Receptors

• Part of it functions as an enzyme1. Ligand binds causing two receptor

polypeptides to aggregate, forming a dimer