Chapter 11 Cell Communication

Introduction All living cells, across all domains, possess the same basic chemical processes needed for cell to cell communication. Communication schemes are the products of evolution and are shared across evolutionary lines of descent. Chemical signals allow cells to communicate without physical contact.

Chemical signals can be: a molecule, such as a hormone or a neurotransmitter. a physical or an environmental factor, such as light or touch. Receptors are proteins that either change shape or aggregate when a specific signal molecule binds to it. This ultimately results in a change in gene expression, protein activity, or physiological state of the cell/organism.

Signal Transduction Pathway All chemical signals induce a response in the cells that receive it. The process by which a signal on a cell’s surface is converted into a specific cellular response through a series of steps  SIGNAL TRANSDUCTION PATHWAY In unicells, STP influence cell to environment communication.

Multicells use STP for cell to environment and cell to cell communication. To coordinate activities with in individual cells that support the function of the organism as a whole.

Cell to cell communication can take place over short distances by using local regulators that target cells within the vicinity of the signal emitting cell.

Cell to cell communication can take place over long distances by using signal molecules that travel.

Overview Chemical signals allow cells to communicate with physical contact. Chemical signaling pathways in cells are determined buy the molecules involved, the concentrations of signals and receptors, and the binding affinities between signals and receptor. Defects in the signal pathway often result in faulty development, metabolic diseases, cancer or death.

3 stages in STP Reception: Target cell receptor proteins (either intra or inter) recognize a signal molecule (ligand) coming from the outside of the cell.

2. Transduction: The binding of the signal molecule causes a shape change to the receptor protein in some way, initiating the process of transduction.

3. Response: The bound receptor/ligand triggers a specific cellular response.

Signaling Cascades Cascades allow the signal to be amplified to increase the number of activated molecules at the end of the pathway. Usually involve second messenger molecules that relay signals received at receptors on the cell surface to target molecules in the cells cytoplasm or nucleus.

3 major classes Cyclic nucleotides – cAMP, cGMP Inositol triphosphate (IP3) Ca+2