Signal Transduction Practice Flashcards

A set of comprehensive flashcards covering receptor types, G-protein signaling, second messengers, ion channels, and catalytic receptors based on lecture notes.

What is a receptor?

A protein molecule found on the surface of a cell or in the cytoplasm/nucleus that receives specific chemical signals, instructing the cell to perform actions like dividing, dying, or allowing molecules to enter/exit.

What are the two major classes of receptors?

(A) Cell surface/Membrane associated (Extracellular Receptors) and (B) Intracellular Receptors.

What is the formula for the dissociation constant ($K_D$)?

$K_D = \frac{[R][L]}{[RL]}$ where $[R]$ is the receptor concentration, $[L]$ is the ligand concentration, and $[RL]$ is the receptor-ligand complex concentration.

Match the binding affinity value ($K_d$) for the adrenergic ligand Isoproterenol.

$$0.4\,\mu M$$

Which scientist discovered how the hormone epinephrine acts on cells and proposed the three stages of cell signaling?

Earl W. Sutherland

What are the three stages of cell signaling?

Reception, Transduction, and Response.

What structural feature characterizes G protein-coupled receptors (GPCRs)?

They are integral membrane proteins possessing seven transmembrane helices/domains ($7-TM\alpha$ helices).

When is a G protein considered to be in the 'on' or active state?

When the GPCR/G protein is bound with $GTP$.

What transition occurs to turn the G protein 'off'?

When it binds with $GDP$ or the $GTP$ is hydrolyzed to $GDP$.

What are the subunits of a heterotrimeric G protein?

Alpha ($\alpha$), beta ($\beta$), and gamma ($\gamma$) subunits.

Provide an example of a small (monomeric) G protein involved in growth factor signal cascades.

Ras

Which adrenergic receptor subtypes are linked to Gs proteins and produce a rise in cAMP?

$\beta_1$, $\beta_2$, and $\beta_3$

What are the primary downstream effectors of cAMP?

cAMP-dependent protein kinase A ($PKA$).

What enzyme is responsible for the formation of cAMP from ATP?

Adenylyl cyclase

What enzyme catalyzes the degradation of cAMP to $5'-AMP$?

Cyclic nucleotide phosphodiesterase

What are the two second messengers produced by the action of Phospholipase-C ($PLC$)?

Inositol triphosphate ($IP_3$) and diacylglycerol ($DAG$).

What is the specific function of $IP_3$ in the phosphoinositide signaling cascade?

It diffuses to the interior of the cell to bind and release $Ca^{2+}$ from intracellular stores (Endoplasmic Reticulum).

How does Diacylglycerol ($DAG$) function in signaling?

It activates the effector enzyme Protein Kinase-C ($PK-C$).

What calcium-binding protein forms a complex with four high-affinity $Ca^{2+}$ binding sites?

Calmodulin (CaM)

Which neurotransmitters trigger the opening of cation channels ($K^+$, $Na^{2+}$, $Ca^{2+}$) causing excitation?

Serotonin ($5-hydroxytryptamine$) and Glutamate.

What toxins act by blocking voltage-gated $Na^+$ channels, preventing normal action potentials?

Tetrodotoxin (produced by puffer fish) and Saxitoxin (produced by marine dinoflagellates).

What is the characteristic action of Receptor Tyrosine Kinases ($RTKs$) upon ligand binding?

They attach phosphates to tyrosines ($Y$) via auto-phosphorylation of the cytosolic domain.

What anticancer drug was developed to target RTKs and used for Chronic myelogenous leukemia ($CML$)?

Imatinib

What is the linear series of Ser/Thr kinases that form the signaling pathway downstream of Ras?

The MAP kinase cascade ($Raf \rightarrow Mek \rightarrow MAPK$).

Which signaling pathway is typically activated by cytokines to control inflammatory mediators?

The Jak/Stat pathway.

What are the five distinct regions in the molecular structure of a Steroid Hormone Receptor ($SHR$)?

N terminal, C terminal, Hinge region, DNA binding domain, and Ligand binding domain.