Cell Communication

• Sending cell


  Cell that communicates to other cells usually with chemical signals made up of proteins or other molecules
• Target cell


  Cell that detects the signals sent by the sending cell with its receptors
• Ligand


  General term for a molecule that specifically binds to other molecules, like receptors
• Intercellular signal


  Signal between cells
• Intracellular signal


  Signal within a cell
• Paracine signaling


  When cells communicate over relatively short distances through ligands, allowing cells to locally coordinate with their neighbors. Important in development when clumps tell each other what they should become
• Synaptic signaling


  Unique type of paracine signaling where electrical impulses in neurons trigger their axon terminals to release neurotransmitter (ligands)
• Synapse


  Junction between two nerve cells where signal transmission occurs
• Autocrine signaling


  When a cell sends signals that bind to its own receptors. Important in dev because it affirms what cells do
• Endocrine signaling


  When hormones are put into the bloodstream and carried to far-off targets. Long-distance form of cell signaling that involves the pituitary gland, hypothalamus, thyroid, and gonads
• Hormone


  Signal that is produced in one part of the body and travels to another through the circulatory system
• Growth hormone (GH)


  Hormone released by the pituitary gland that helps us develop bigger bones and more cartilage, amongst other things, by telling cells to multiply faster
• Gap junctions


  Tiny channels that directly connect neighboring cells. When one cell changes state it transfers it to its neighbors
• Intracellular mediators


  Small signaling molecules that are able to diffuse through the gap junctions
• Signaling through cell-cell contact


  Using things like gap junctions or two cells with complimentary surface proteins binding to each other, sending signals through multiple cells when one interaction happens
• Quorum sensing


  When unicellular organisms use chemical signals from each other to see how dense the population is. Their gene expression and behaviors change if it gets too dense
• Some organisms have evolved together so that unicellular organisms symbiotically use quorum sensing to see whether or not they're in their host so they can activate their otherwise useless thing that helps (e.g. bacteria becoming bioluminescent inside of a squid, protecting it from predators in exchange for food)
• Autoinducers


  Signaling molecules that are continually secreted by bacteria to alert their neighbors of their presence, letting then detect cell density and coordinate
• Each species of bacteria has its own autoinducer that will diffuse out until they're in higher concentrations, when it will start to bind to other cells, affecting DNA transcription, leading to changes in gene expression
• Biofilm


  When some species of quorum-sensing bacteria form surface-attached communities that cover the substrate (thing beneath them). Can be made up of multiple coexisting colonies
• Mating factor


  Signaling chemical that lets fungi who reproduce sexually find each other
• Plasmodemata


  Specialized junctions in plant cells where a hole is punched in the cell wall to allow direct cytoplasmic exchange between them. Lined with a shared membrane with a super thin strand of ER in the cytoplasm. Can dilate to let proteins through but usually its just tiny molecules diffusing
• Connexins

  6 proteins that make up the connexon
• Connexon


  Donut like structure between two animal cells that make up a gap junction
• Tight junctions


  Watertight seal between two adjacent animal cells that stop water from escaping between two of them. Important in things like linings where you don't want liquids escaping
• Claudins


  Proteins that make up a tight junction
• Desmosomes


  Animal cell junctions that hold cells together, like making sure the epithelium stays in one sheet when it stretches
• Cadherins


  Specialized adhesion proteins that are found along the membranes of cells in desmosomes, both connecting cells on the outside through membranes and anchoring to red cytoplasmic plaque and intermediate filaments on the inside of the cell