Overview
This lecture provides an overview of the main ways that cells communicate with each other, focusing on direct contact, local signaling, and long-distance signaling.
Direct Contact Communication
- Cells can communicate by direct contact through gaps in their membranes.
- In animal cells, these gaps are called gap junctions.
- In plant cells, similar channels are called plasmodesmata, which pass through both the membrane and cell wall.
- Neighboring cells can exchange small molecules via these junctions, leading to responses in the receiving cell.
- Some cells communicate by binding complementary surface proteins, which can trigger reactions in both cells.
Local and Long-Distance Signaling
- Cells can release signaling molecules into the extracellular space to affect nearby or distant cells.
- Target cells must have the correct receptor to respond to the signaling molecule.
- Local communication over short distances is called paracrine signaling; the molecules are called paracrine factors.
- Long-distance signaling through the bloodstream is called endocrine signaling, involving molecules known as hormones.
- The same cell that releases the signal can sometimes respond to it, known as autocrine signaling.
Signal Reception and Response
- Receptors are proteins on the cell surface or inside the cell that bind signaling molecules.
- The signaling molecule that binds to a receptor is called a ligand.
- Signal perception occurs when the ligand binds to its receptor.
- Signal transduction refers to the process of transmitting the signal inside the cell, leading to a cellular response.
Key Terms & Definitions
- Gap Junction — a channel connecting adjacent animal cells for communication.
- Plasmodesmata — channels through plant cell walls for communication.
- Receptor — a protein that binds signaling molecules and receives signals.
- Ligand — a general term for any molecule that binds to a receptor.
- Paracrine signaling — local cell signaling over short distances using paracrine factors.
- Endocrine signaling — long-distance signaling via the bloodstream using hormones.
- Autocrine signaling — a cell responds to signals it produces itself.
- Signal transduction — the process of transmitting a signal into a cell to elicit a response.
Action Items / Next Steps
- Review the structure and function of gap junctions and plasmodesmata.
- Prepare for future lessons on the endocrine system and hormone signaling.