Cell Communication and Signaling Pathways

Signal-Transduction Pathway

Process converting surface signals into cellular responses.

Evolutionary History

Cell signaling evolved from prokaryotes to multicellular organisms.

Local Regulators

Signaling molecules influencing nearby cells.

Paracrine Signaling

Multiple cells respond to a single cell's growth factors.

Synaptic Signaling

Nerve cell releases neurotransmitters to adjacent cells.

Hormones

Chemical messengers signaling over long distances.

Endocrine Cells

Cells releasing hormones into the circulatory system.

Direct Contact Communication

Substances pass between adjacent cells.

Reception Stage

Chemical signal binds to cellular receptor proteins.

Transduction Stage

Binding triggers changes along a signaling pathway.

Response Stage

Transduced signal activates specific cellular activities.

Ligands

Small molecules binding specifically to larger molecules.

G-Protein-Linked Receptors

Receptors associated with G-proteins on the cytoplasmic side.

Tyrosine-Kinase Receptors

Receptors regulating multiple activities via phosphorylation.

Ligand-Gated Ion Channels

Protein pores opening in response to chemical signals.

Phosphorylation

Addition of phosphate groups to regulate protein activity.

Protein Kinase

Enzyme transferring phosphate from ATP to proteins.

Protein Phosphatases

Enzymes removing phosphate groups to turn off pathways.

Second Messengers

Small molecules amplifying signaling pathways.

Cyclic AMP

Important second messenger in signaling pathways.

Calcium Ions (Ca2+)

Key second messenger influencing various cellular processes.

Glycogen Breakdown

Process stimulated by epinephrine through signaling pathways.

Amplification of Signals

Multistep pathways increase cellular response magnitude.

Specificity of Response

Different cells respond uniquely to the same signal.

Scaffolding Proteins

Proteins enhancing speed and accuracy of signal transfer.

Transcription Factors

Proteins controlling gene expression in response to signals.

Cellular Response

Outcome of signal transduction affecting cell function.