Untitled Deck Flashcards
What do cell-surface receptors do?
Cell-surface receptors relay signals into the cell by triggering intracellular signaling molecules that alter effector proteins and modify cell behavior.
What are second messengers?
Small chemicals generated in response to receptor activation, such as cyclic AMP, Ca²⁺, and diacylglycerol, which spread signals within the cell.
How do second messengers pass signals?
By binding to and altering the behavior of signaling or effector proteins.
What is the most common type of intracellular signaling molecule?
Proteins, which relay signals by generating second messengers or activating other signaling or effector proteins.
How do molecular switches work?
They switch between inactive and active states when receiving a signal and must return to their inactive state to reset the pathway.
What is the largest class of molecular switches?
Proteins regulated by phosphorylation, controlled by protein kinases and phosphatases.
What do protein kinases do?
Covalently add phosphate groups to specific amino acids on target proteins, activating them.
What do protein phosphatases do?
Remove phosphate groups from proteins, deactivating them.
What are the two main types of protein kinases?
Serine/threonine kinases (phosphorylate serine/threonine) and tyrosine kinases (phosphorylate tyrosine).
What is a kinase cascade?
A sequence of protein kinases where one kinase activates the next, amplifying or spreading the signal.
What is the second major class of molecular switches?
GTP-binding proteins, which switch between an active state (GTP-bound) and an inactive state (GDP-bound).
What do GTPase-activating proteins (GAPs) do?
Drive GTP-binding proteins into the “off” state by increasing the rate of GTP hydrolysis.
What do guanine nucleotide exchange factors (GEFs) do?
Activate GTP-binding proteins by promoting the release of GDP, allowing GTP to bind.
What are the two types of GTP-binding proteins?
Large, trimeric G proteins (relay signals from G-protein-coupled receptors) and small monomeric GTPases (relay signals from various receptors).
What regulates trimeric G proteins?
The activated receptor acts as the guanine nucleotide exchange factor (GEF).
