Cell Signaling Pathways Quiz

G-protein-linked receptors are a large family of cell-surface receptors that bind to a variety of extracellular signal molecules, such as hormones, neurotransmitters, and local mediators.

All G-protein-linked receptors have a similar structure: a single polypeptide chain that crosses the cell membrane seven times. This seven-transmembrane structure allows them to interact with both extracellular signals and intracellular signaling pathways.

G-proteins are heterotrimeric proteins, meaning they consist of three subunits: alpha (α), beta (β), and gamma (γ). The alpha subunit binds to GTP and can hydrolyze it to GDP and phosphate.

When an extracellular signal molecule binds to a G-protein-linked receptor, the receptor undergoes a conformational change that activates the G-protein. The activated G-protein then interacts with downstream effector proteins to initiate a signaling cascade.

The alpha subunit of the G-protein is responsible for activating downstream effector proteins. Different types of G-proteins activate different effector proteins, leading to a diverse range of cellular responses.

Primary messengers are extracellular signaling molecules that bind to receptors on the cell surface. Secondary messengers are small molecules that are generated inside the cell in response to the activation of a receptor. These messengers act as intracellular signals, relaying information to other components of the cell.

G-proteins are highly specific: different G-proteins interact with different receptors and activate different downstream effector proteins. This specificity ensures that each signal molecule triggers the appropriate cellular response.

The diversity of G-protein-linked receptors and G-proteins allows cells to respond to a wide range of extracellular signals. This diversity is essential for coordinating complex cellular processes and maintaining normal physiological function.

Activated by a ligand binding to a GPCR, the G protein releases GDP and binds GTP, leading to its activation and dissociation into the α subunit and βγ complex.

A transmembrane protein that produces cAMP, a small intracellular signaling molecule.

A type of signaling pathway that involves a G protein interacting with adenylate cyclase.

A second messenger that activates protein kinase A (PKA) in many pathways.

A type of cell surface receptor with seven transmembrane helices. It activates G proteins by binding to ligands.

The activated α subunit of the G protein binds to and activates adenylate cyclase, leading to cAMP production.

A complex of β and γ subunits that can also regulate target proteins.

The process by which a signal is received by a cell and transduced into a response.

cAMP, a secondary messenger, is synthesized from ATP by adenylyl cyclase, an enzyme activated by the activated alpha subunit of a G-protein.

cAMP phosphodiesterase rapidly converts cAMP to AMP, helping to eliminate the signal and restore the cell to its resting state.

cAMP-dependent protein kinase (PKA) is the main mediator of cAMP's effects. It phosphorylates various cellular proteins, altering their activity.

PKA phosphorylates gene regulatory proteins, activating the transcription of a specific set of target genes.

The inositol phospholipid pathway activates phospholipase C, a membrane-bound enzyme that cleaves phosphatidylinositol, generating two important second messengers: inositol-1,4,5-trisphosphate (InsP3) and diacylglycerol (DAG).

InsP3 triggers the release of calcium ions (Ca2+) from intracellular stores, leading to a rise in intracellular Ca2+ concentration.

Diacylglycerol (DAG) activates protein kinase C (PKC), another important signaling protein.

Ca2+ acts as a crucial intracellular messenger, playing a vital role in numerous biological processes by binding and activating various proteins, including calmodulin-binding proteins, specific kinases, and phosphatases.

A type of protein that binds to calcium ions (Ca2+) and acts as a mediator of calcium signaling. It is involved in a wide range of cellular processes, including muscle contraction, neurotransmission, and gene expression.

The G protein subunit responsible for activating downstream effector proteins. The activation of the G protein is triggered by the exchange of GDP for GTP.

The process in which a signal is received by a cell and converted into a response.

A type of signaling pathway that involves the production of inositol triphosphate (IP3) and diacylglycerol (DAG) as second messengers. It is often triggered by the activation of G protein-coupled receptors.

A specialized type of G protein that regulates the opening of potassium (K+) channels in the membrane of cardiac muscle cells. This affects the heart's rhythm and contraction.

A specific type of intracellular signaling molecule that is produced by the enzyme adenylate cyclase. It acts as a second messenger in many cellular pathways, including those involved in metabolism, growth, and development.

They act as intracellular signals, relaying information to other components of the cell.

It describes how a signal is amplified within a cell, leading to a stronger response. This can occur through various mechanisms, such as the activation of multiple downstream signaling molecules.

Proteins that act like a bridge, connecting multiple signaling proteins within the same pathway.

The process by which a cell stops responding to a signal, ensuring that signaling pathways are transient and do not continue unnecessarily.

The activated Gα subunit hydrolyzes its bound GTP to GDP, returning to its inactive state and dissociating from adenylate cyclase.

An enzyme responsible for breaking down cAMP, a key second messenger in signal transduction.

A phosphorylated receptor can bind to β-arrestin, preventing further interaction with G-proteins and effectively stopping the signal.

The ability of cells to respond differently to the same signaling molecule due to variations in their protein composition and signaling pathways.

Interactions between different signaling pathways, allowing cells to coordinate complex responses to multiple stimuli.

The presence of branching points in a signaling pathway, allowing for the activation of multiple downstream targets.

β-Arrestin is a protein that helps shut off G protein-coupled receptor (GPCR) signaling by promoting its endocytosis and by binding to phosphodiesterase, which breaks down cAMP.

V. cholera enterotoxin modifies the α subunit of the Gs protein, preventing its inactivation by GTPase. This keeps the Gs permanently activated, leading to continuous cAMP production and severe diarrhea.

Protein phosphatases reverse the effects of protein kinases by removing phosphate groups from proteins. They are essential for turning off signaling cascades by returning target proteins to their original, inactive states.

cAMP activates protein kinase A (PKA), which phosphorylates target proteins to activate them. When the signal needs to be switched off, protein phosphatases remove these phosphate groups, deactivating the target proteins and reversing the signal.

G protein-coupled receptors (GPCRs) are a large family of cell surface receptors that activate G proteins. They are involved in various signaling pathways and play a crucial role in regulating a wide range of cellular processes.