Cellular Signaling and Communication Quiz

Chemical messengers that travel between cells to coordinate activities.

Proteins on the cell surface that bind to specific signal molecules, initiating a response.

Chains of molecules within a cell that relay and amplify signals from the cell surface to intracellular targets.

Proteins that carry out the final response to a signal, such as altering gene expression, changing metabolic activity, or modifying the cytoskeleton.

The process by which signaling molecules are released from the signaling cell into the extracellular space.

Signaling that occurs between cells in direct physical contact.

Signaling that occurs over long distances, where the signal molecule travels through the bloodstream.

The specific binding of a signal molecule to its receptor, initiating a cascade of events inside the cell.

In synaptic signaling, specificity is achieved by the direct connections between nerve cells and their target cells. Only the target cell in direct contact receives the neurotransmitter.

Neurotransmitters can also act as local messengers, influencing multiple nearby cells, but this is not their primary function.

Endocrine signals are released into the bloodstream, reaching a wider audience, while neuronal signals are targeted to specific cells via synapses.

The speed of a cellular response depends on the signal delivery method and the cell's internal mechanisms.

Changes in cell movement, secretion, and metabolism can occur quickly using existing proteins, without needing new gene expression.

Growth and division involve changes in gene expression, therefore requiring more time to synthesize new proteins.

Gap junctions are direct channels connecting the cytoplasm of neighboring cells.

Gap junctions allow the exchange of small molecules, including signaling molecules like cyclic AMP and Ca2+, but not large molecules like proteins or nucleic acids.

Certain G proteins directly activate or deactivate ion channels in the plasma membrane of the target cell, altering its ion permeability and electrical excitability.

Acetylcholine, released by a nerve, can reduce heart muscle contraction. This effect is mediated by acetylcholine receptors that activate the Gi protein, leading to inhibition of adenylyl cyclase and opening of K+ channels in the heart muscle cell membrane.

GPCR desensitization occurs when cells are exposed to high levels of a stimulating ligand for a prolonged period. This adaptation involves GPCR kinases (GRKs) phosphorylating activated receptors and recruiting arrestin, which prevents further G protein binding and directs receptor endocytosis.

Enzyme-coupled receptors are transmembrane proteins with their ligand-binding domain on the external surface of the plasma membrane. Their cytosolic domain either has intrinsic enzyme activity or associates directly with an enzyme. Unlike GPCRs, they usually have only one transmembrane segment per subunit.

These receptors directly phosphorylate specific tyrosines on themselves and a few intracellular signaling proteins.

These receptors lack intrinsic enzyme activity but recruit cytoplasmic tyrosine kinases to relay the signal.

Cells need multiple signals to survive, grow, and differentiate. Without these signals, they can undergo programmed cell death (apoptosis).

Different cells respond differently to the same signal molecule due to variations in their receptor proteins and intracellular signaling pathways.

A signaling molecule released from a localized source during development, creating a concentration gradient that induces different cell fates.

Different concentrations of a morphogen lead to different gene expression patterns, resulting in various cell fates.

A cell's response to extracellular signals depends on its receptor proteins and the ability to interpret the signals via intracellular pathways.

Acetylcholine, a neurotransmitter, can elicit different responses in different cell types due to variations in receptors and/or intracellular signaling pathways.

Cells utilize both activating and inhibiting extracellular signals to regulate their behavior. Inhibitory signals can also initiate apoptosis.

The cell's response to a signal is determined by the combination of activating and inhibiting signals received.

A specific protein kinase activated by cAMP, which in turn phosphorylates CREB, leading to gene transcription.

A protein that binds to cAMP and activates PKA, triggering a signaling cascade.

A transcription factor that, when phosphorylated by PKA, recruits CBP to activate gene transcription.

A protein that acts as a transcriptional coactivator, working with phosphorylated CREB to stimulate gene expression.

A key enzyme in inositol phospholipid signaling pathway, activated by Gq protein, which hydrolyzes PIP2 into IP3 and DAG.

A second messenger produced by PLC-β; it diffuses through the cytosol and binds to IP3 receptors on the ER membrane, triggering Ca2+ release.

A second messenger generated by PLC-β; it remains in the plasma membrane and, along with Ca2+, activates protein kinase C (PKC).

A protein kinase activated by Ca2+ and DAG, playing various roles in cellular signaling, including gene expression and cell growth.

A large family of cell surface receptors, found in all eukaryotes, that are involved in sensing a wide range of stimuli, such as light, odor, and taste.

GPCRs have a unique structure, consisting of a single polypeptide chain that traverses the cell membrane seven times.

GPCRs utilize G proteins to relay signals into the cell interior. When an extracellular signal molecule binds to a GPCR, it causes a conformational change in the receptor, which activates a G protein.

G proteins are trimeric proteins, consisting of alpha, beta, and gamma subunits. In their inactive state, the alpha subunit binds to GDP. Upon activation by a GPCR, the alpha subunit releases GDP and binds GTP, causing a conformational change that activates the G protein.

The activated alpha subunit of the G protein interacts with downstream effector proteins, such as enzymes or ion channels, to initiate a cellular response.

The alpha subunit possesses GTPase activity, meaning it can hydrolyze GTP back to GDP, inactivating the G protein. This intrinsic GTPase activity helps to regulate the duration of the signal.

GPCRs are highly diverse, with over 700 different GPCRs in humans. This diversity allows for a wide range of signaling events to occur in response to different stimuli.

Different GPCRs can be activated by the same signal molecule. For example, adrenaline activates at least 9 distinct GPCRs. This allows for the same signal to trigger different responses in different cell types.