Cell Communication

My AP Biology Thoughts

My AP Biology Thoughts

Unit 4 Cell Communication and Cell Cycle

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.

Segment 1: Introduction to Cell Communication

• 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

Segment 2: More About Cell Communication

• Cell-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 have received
• This is especially important for responses in the immune system and with recognition
• Below is a diagram of an immune system cell recognizing a healthy cell:
• When the proteins bind to one another, this interaction changes the shape of one or both proteins, transmitting a signal
• This kind of signaling is especially important in the immune system, where immune cells use cell-surface markers to recognize the body's own cells and cells infected by pathogens
• Next, in paracrine signaling, signals bind through communication over relatively short distances through the release of chemical messengers
• This type of signaling is important because it allows cells to communicate with other nearby cells and during development when they allow one group of cells to tell a neighboring group of cells what cellular identity to take on
• A type of paracrine signaling is synaptic signaling in which nerve cells transmit signals through the synapse which is the junction between two nerve cells where signal transmission occurs
• Finally, the last type of signaling is called endocrine sigaling which occurs when cells need to transmit signals over long distances where the circulatory system is often used as a way for the messages to be transmitted
• Signals are produced by specialized cells and released into the bloodstream which carries them to target cells in other parts of the body
• Signals that are produced in one part of the body and that travel through the circulation to reach other “far-away” targets are called hormones
• Endocrine glands that secrete hormones are called thyroid, the hypothalamus, and the pituitary, and each one releases one or more types of hormones, many of which are strong regulators of development and physiology
• Below is a diagram of how this signaling works and you can see how the message is sent through the bloodstream between two different cells

Segment 3: Connection to the Course

• Cell communication fits into the bigger picture of this unit which is cell communication and the cell cycle because in order for the body to function properly, the cells need to work together through communication and signals
• This process is important because it allows cells to fine-tune their functions and be able to communicate well and errors in communication can be detrimental and lead to cancer or diabetes which is why the cell cycle is also so important

Thank you for listening to this episode of My AP Biology Thoughts. For more student-ran podcasts and digital content, make sure that you visit www.hvspn.com.

Music Credits:

• "Ice Flow" Kevin MacLeod (incompetech.com)
• Licensed under Creative Commons: By Attribution 4.0 License
• http://creativecommons.org/licenses/by/4.0/

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