My AP Biology Thoughts  Unit 4 Cell Communication and Cell CycleWelcome 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.  Segment 1: Introduction to Cell CommunicationSo, 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 http://www.nature.com/scitable/topicpage/p53-the-most-frequently-altered-gene-in-14192717 (modulation of gene expression) Metabolites in the blood that can trigger a cell's receptors to cause the release of a hormone needed for http://www.nature.com/scitable/topicpage/g-protein-coupled-receptors-pancreatic-islets-and-14257267 (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

Segment 2: More About Cell CommunicationCell-cell signaling involves the transmission of a signal from a sending cell to a receiving cell, but not all cells exchange signals in the same way because cells are exposed to many signals and may have different responses  The 4 basic categories of cell signaling are, autocrine, juxtacrine, paracrine, and endocrine signaling with the main differences between them being the distance that the signal itself travels So, first, in autocrine signaling, the cell signals to itself and a great example of this are tumor cells because of their ability to produce and respond to their own growth factors The cell releases a ligand that binds to receptors on its own surface or to receptors inside of the cell This signaling is important because during development, cells take on their own identities and reinforce them In juxtacrine signaling, direct contact between cells is required, and the transfer of signaling molecules transmits the current state of one cell to its neighbor which allows a group of cells to coordinate their response to a signal that only one of them may...