G Protein-Coupled Receptor Functions

This video tutorial covers the basics of G protein-coupled receptors (GPCRs), the largest and most diverse group of membrane receptors in eukaryotes. It explains the structure of GPCRs, highlighting their seven transmembrane domains and the positioning of the N-terminal and C-terminal domains. The video details the function of the heterotrimeric stimulatory G protein (GS), its domains, and the activation mechanism involving GDP and GTP. The process of signal transduction through adenyl cyclase and cAMP is discussed, along with the deactivation and recycling of the G protein subunits.

What is the primary characteristic of G protein-coupled receptors that makes them significant in eukaryotes?

• They are the smallest group of membrane receptors.

• They do not span the plasma membrane.

• They are the most diverse group of membrane receptors.

• They are only found in prokaryotes.

How many times does the G protein-coupled receptor span the plasma membrane?

• Five times

• Eight times

• Six times

• Seven times

Where is the n-terminal domain of the G protein-coupled receptor located?

• Within the cell nucleus

• In the mitochondria

• In the outer environment

• In the cytoplasm

What is the role of the c-terminal domain in G protein-coupled receptors?

• It interacts with the mitochondria.

• It attaches to the heterotrimeric stimulatory G protein.

• It is responsible for DNA replication.

• It binds to the cell nucleus.

Which subunit of the stimulatory G protein is usually attached with GDP in its inactive state?

• Delta subunit

• Alpha subunit

• Gamma subunit

• Beta subunit

What happens when a signaling molecule binds to the G protein-coupled receptor?

• The receptor is deactivated.

• The GDP is replaced by GTP on the alpha subunit.

• The receptor is destroyed.

• The receptor moves to the nucleus.

What enzyme does the activated alpha subunit interact with?

• DNA polymerase

• Lactase

• Adenyl cyclase

• RNA polymerase

What is the function of adenyl cyclase in the signaling pathway?

• It synthesizes DNA.

• It catalyzes the formation of cAMP from ATP.

• It deactivates the receptor.

• It breaks down proteins.

What does cyclic AMP activate in the cell?

• Protein kinase A

• DNA helicase

• RNA polymerase

• Lactase

How does the alpha subunit return to its inactive state?

• By detaching from the receptor

• By hydrolyzing GTP to GDP

• By moving to the nucleus

• By binding to ATP