Welcome to My AP Biology Thoughts podcast, my name is Shriya Karthikvatsan and I am your host for episode #81 called Unit 4 Cell Communication and Cell Cycle: Cell Communication. Today we will be discussing how cells communicate with one another and how they do over long and short distances. 

• So, the topic of cell communication focuses on how a cell gives and receives messages with its environment and within itself because a cell’s survival depends on its ability to receive and process information outside its environment
• The cell membrane plays a key role in a cell’s response to environmental signals because there are chemical and physical signals that a cell has to respond to via receptors 
• In membrane signaling, proteins shaped into receptors are embedded in the membrane which connect the triggers in the external environment to the ongoing dynamics inside a cell
• In addition, ion channels allow the direct passage of molecules between external and internal compartments of the cell
• Cells have evolved a variety of mechanisms to be able to transmit important biological information and some examples include:
• The development of growth factors that interact with the cell membrane and can trigger receptors that powerfully affect the modulation of gene expression
• Metabolites in the blood that can trigger a cell's receptors to cause the release of a hormone needed for glucose regulation
• Now, we will go into an overview of cell communication and some important terms to note
• Since we know cells communicate using signals, we should also know that these chemical signals are proteins produced by a “sending cell” which are released into the extracellular space where the signal can be “heard”
• In order to detect a signal, or to be a target cell, a neighbor cell must have the right receptor for that signal
• When a signaling molecule binds to its receptor, it alters the shape or activity of the receptor, triggering a change inside of the cell and signaling molecules are often called ligands
• The message carried by a ligand is often put through a chain of chemical messengers inside the cell which leads to a change in the cell, such as alteration in the activity of a gene or cell division
• Finally, the original intercellular (between-cells) signal is converted into an intracellular (within-cell) signal that triggers a response
• You can see what I am talking about in the diagram below:
• In the next segment, we will go more into detail of the 4 types of cell signaling, their meanings, and why they are important

• Cell-cell signaling involves the transmission of a signal from a sending cell to a receiving cell, but not all cells...