My AP Biology Thoughts
Unit 4 Cell Communication and Cell Cycle
Welcome to My AP Biology Thoughts podcast, my name is Nikki Evich and I am your host for episode
#82 called Unit 4 Cell Communication and Cell Cycle: Intro to Signaling Transduction Pathway. Today
we will be discussing the components that make up a pathway.
Segment 1: Introduction to the signaling transduction pathway
● Signal also call ligand binds to a receptor on target cell membrane
○ , starts the pathway,
○ had to fit receptor,
○ once bound, transduction is initiated
● Receptor- intracellular or extracellular
○ Binding domain recognizes specific chemical messengers
● transduction-lots of varian with transduction
○ Could activate inactive protein by phosphorylating
○ Amplifies with secondary messengers
● Response- what the end result is
○ Can be short or long
○ Activate enzyme or move cell-short
○ Alter gene expression levels or cell division (apoptosis)-long
Segment 2: More About the signaling transduction pathway
● Type 1
● Once the food is broken down into glucose, these molecules are then absorbed into the bloodstream.
The high glucose levels in the bloodstream activate the beta cells in the pancreas to start producing
insulin. Insulin is a hormone created in the pancreas. In the pancreas, beta cells are present which are
in charge of secreting the insulin into the bloodstream once they detect an increase in blood glucose.
Insulin travels to three main destinations-muscle, fat, and liver cells.
● This is where the transduction pathway happens
● The insulin will then bind to the insulin receptors. The insulin receptors are made up of extracellular
alpha subunits and transmembrane beta subunits.
● When the insulin binds to the extracellular alpha subunits, the beta subunits become activated and auto
phosphorylate. This means that they phosphorylate themselves.
● This leads to the phosphorylation and activation of the IRS protein. The IRS protein is regulated and
can be phosphorylated by PTEN. PTEN can regulate phosphorylation and activate IRS Isaforms by
dephosphorylating IRS. Once IRS is activated, proteins including PI3K will bind to the IRS protein
through their P85 subunit.
● The PI3K will then phosphorylate PIP2 to PIP3. When the PIP3 concentration increases, other proteins
like PDK1 and AKT are recruited towards the plasma membrane. PIP3 activates PDK1 which then
● Cells have reservoirs of intracellular vesicles that contain GLUT4, a glucose transporter. So in order for
glucose to be let into the cell the glucose transporters have to translocate to the plasma membrane.
However, AS160 inhibits this process.
● Luckily, phosphorylated AKT inactivates AS160. So when AKT is phosphorylated by PDK1, AS160 is
inactivated which in turn allows for the translocation of glut 4 so it can embed itself in the membrane.
Now glucose can get into the cell for storage and other purposes.
Segment 3: Connection to the Course
● Involved in evolution-some cell transduction pathways stayed the same
○ Track common ancestors Interruptions in this pathway are serious like with the brain sending
● Involved in negative feedback loops and homeostasis
● Body is constantly sending signals, though it may seem minute it makes you be able to do all you do
● In all walks of life
● Can be seen in all types of diseases and illness from Diabetes to cancer
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. Bye now!
● “Ice Flow” Kevin MacLeod (incompetech.com)
● Licensed under Creative Commons: By Attribution 4.0 License
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