Reception: G Protein Receptors, Tyrosine Kinase Receptors

My AP Biology Thoughts Unit 4 Cell Communication and Cell Cycle

Welcome to My AP Biology Thoughts podcast, my name is Sid and I am your host for episode #86 called Unit 4 Cell Communication and Cell Cycle: G Protein Receptors and Tyrosine Kinase Receptors.

Segment 1: Introduction to G protein receptors and tyrosine kinase receptors

• G Protein receptors and tyrosine kinase receptors both work to mediate cell communication by binding a signaling molecule, which is also called a ligand. Then this signal is sent through a transduction pathway where the last target protein causes some response. The response for both can be a variety of things such as gene expression, apoptosis, metabolic responses, cell division, or cell growth. Despite being similar in this way, g protein receptors and tyrosine kinase receptors work in very different ways

Segment 2: More About G protein receptors

• Let's start by discussing g protein receptors. G proteins are very diverse and can bind to many different signals. One example is odorant (or scent) receptors. G proteins receptors are located in the cell membrane which is where an extracellular ligand binds to it. The signal is eventually sent to a g protein which is located on the membrane, but on the cytoplasmic side. Before the G protein is activated, GDP is bound to it which keeps it inactive. GDP is guanosine diphosphate. After the signal binds to the receptor, the receptor slightly changes shape and becomes active. Then, the GDP binds to the g protein receptor. Since the G protein no longer has a GDP bound to it, it frees it up to accept and bind to GTP. The GTP activates the G protein. The G protein is made up of three subunits: alpha, beta, and gamma. When the GTP is bound to the G protein and activates it, the alpha subunit detaches and moves away from the receptor. Now the G protein is split into two parts: one part is the single alpha subunit and the other is the beta and gamma subunits. These two parts can go on to interact with other proteins and cause a transduction pathway that results in one of many responses. Eventually, the alpha subunit comes back and hydrolyzes the GTP which keeps the G protein active and changes it back into GDP. At this point the G protein will once again become inactive. G proteins coupled receptors are very important in the human body. Disruptions can cause diseases like cystic fibrosis or cholera.
• Now let's talk about tyrosine kinase receptors. Tyrosine kinase receptors are enzyme linked receptors. Enzyme linked receptors are receptors that are associated with an enzyme. A kinase is a protein that phosphorylates other proteins. For tyrosine kinase receptors, the kinase phosphorylates tyrosine. To start the process, a signalling molecule attaches to two tyrosine kinase receptors. These come together and form a dimer. Then, each tyrosine kinase receptor phosphorylates the domains of the tyrosine kinase receptor. Then, once the tyrosine is phosphorylated, it can send signals to other molecules

Segment 3: Connection to the Course

• G protein receptors and tyrosine kinase receptors are very important to many species. Problems with g protein receptors can cause choler,