In Episode 13, Melanie recAPs the ways in which cells communicate through cellular signals, called ligands. Do you remember playing telephone as a kid?
In Episode 13, Melanie recAPs the ways in which cells communicate through cellular signals, called ligands. Do you remember playing telephone as a kid?(1:15) Cellular communication is achieved through reception, (1:46) transduction, (2:40) and response (3:27). Signals are classified by the distance that the message has to travel (3:46). Much like the game of telephone, messages are sometimes modified or interrupted (4:51).
The Question of the Day (5:45) asks “Which two enzymes are involved in the phosphorylation cascade?”
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Hi and welcome to the APsolute Recap: Biology Edition. Today’s episode will recap Cell Communication
Lets Zoom out:
Unit 4 - Cell Communication and Cell Cycle
Topic - 4.1-4.4
Big idea - Information storage and transmission
No living thing, cell or organism acts in isolation and every cause has an effect. Combining these two ideas, it makes sense that cells must interact. Cells communicate by generating, transmitting, receiving and responding to chemical signals. In doing so, they are able to respond to and affect environmental changes.
Lets Zoom in:
Have you ever played a game of telephone? Where the first person starts with a sentence as simple as ‘Dogs dig holes for big bones” and as the message goes from person to person ends up as “Donkey nose for pig phones”....which doesn’t even make any sense. Similarly, cellular messages are passed from one cell to the next, and can often be modified along the way. The three main steps of cell communication are reception, transduction and response.
Let's start with reception. Messages are received when a small signal molecule, known as a ligand, binds to a receptor. This often causes the receptor to change shape and triggers the transmission of the message into the cell. Not all receptors can receive all chemical messages. Since they are made of protein, the manner in which they bend and fold will be ligand specific. Remember that cellular membranes have proteins embedded in them. Some of these proteins will have extracellular binding sites to receive chemical signals, like a ligand gated ion channel. G protein-coupled receptors are an example of a receptor protein in eukaryotes. Other receptors will be located within a cell's cytosol, and respond to ligands that are lipid soluble, like steroids. Ligands binding to receptors is often temporary, and can be triggered to dissociate with the end of a signal transduction pathway.
Next, transduction. Signal transduction pathways link signal reception with cellular response. Like a game of mousetrap on display, one molecular interaction will cause the next, passing and often tweaking the message along the way. Many signal transduction pathways include protein modification and phosphorylation cascades. The phosphate added to the process will typically come from a molecule of ATP, temporarily activating each protein in the pathway. Signals are often amplified (or turned up) during each step of the relay - in this way, even a small amount of ligand can have a significant cellular effect. This will involve the use of secondary messengers, such as cyclic AMP.
Lastly, response. There are so many! Some examples include cell growth, secretion of molecules, gene expression or function. This could ultimately modify the physical expersention, phenotype, or even end in apoptosis, programmed cell death.
Cells must communicate with one another along short and long distances in order to respond to environmental changes. Some cells are physically touching, so much so that they share protein tunnels between them for the movement of ions and other molecules. This is true of animal cells with gap junctions or plasmodesmata in plant cells. Immune system cells, such as antigen-present cells and T cells, also interact by cell-to cell contact. Paracrine signaling is a type of local communication - when cells aren’t touching, but are fairly close by. Examples include neurotransmitters across a synapse, the plant cell immune response, quorum sensing in bacteria, as well as morphogens in embryonic development. Endocrine signaling is when signals released by one cell type can travel long distances to target cells of another cell type. This is true for examples such as insulin and hormones, like testosterone, estrogen, and thyroid.
Just like with the game of telephone, sometimes the message can be altered. Any physical, conformational change in any of the signaling molecules may affect the activity of the pathway. These changes might be mutations in the sequence of a receptor protein or an external chemical that activates or inhibits the pathway. Certain pathogens, like viruses, can hijack our cell communication process to their own advantage. Cancer is another example of an error in cell signaling, when cell division continues without functional checkpoints.
To recap….
Cellular communication is crucial to the coordinated efforts of living things. The signaling pathway includes reception, transmission and response. Slight changes in the molecules involved in the transduction pathway can alter the resulting response.
Today’s Question of the day is about phosphorylation.
Question: Which two enzymes are involved in the phosphorylation cascade?