Cell Signaling Flashcards

Flashcards covering key concepts in cell signaling, including types of signaling, receptors, secondary messengers, and signaling pathways.

What is cell signaling?

How cells communicate with each other through receptors and signaling molecules, leading to biological changes within the cell.

What are the possible 'biological changes' that can occur from cell signaling?

Increase or decrease in gene expression or modification of protein function.

What is endocrine signaling?

A type of cell signaling where a gland produces a hormone that travels through the bloodstream to bind to a receptor on a target cell, causing biological changes.

What is paracrine signaling?

A type of cell signaling over short distances where cells in the local environment secrete a signal that binds to a receptor on a target cell, changing its biological function.

How does paracrine signaling differ from endocrine signaling?

Paracrine signaling occurs over short distances and does not involve the bloodstream, unlike endocrine signaling which involves long distances and the bloodstream.

What is neuronal signaling?

Involves the depolarization of a neuron's plasma membrane, leading to the release of neurotransmitters that travel through the synaptic cleft and bind to receptors on the target cell, causing a biological change.

What is contact-dependent signaling?

Signaling where a signaling molecule on the surface of one cell interacts directly with a receptor on the surface of a target cell, requiring physical contact between the cells.

What are the two primary types of receptors that messengers can interact with?

Membrane receptors (on the cell surface) and intracellular receptors (inside the cell).

What kind of molecules bind to membrane-bound receptors?

Large, hydrophobic molecules that cannot cross the plasma membrane.

What kind of molecules bind to intracellular receptors?

Small, hydrophobic molecules that can cross the plasma membrane.

What is a key point regarding cell response to messengers like acetylcholine?

The same molecule can have different biological effects depending on what cell is targeted.

What is apoptosis?

Programmed cell death.

How do cells respond to multiple signals?

Cells integrate multiple signals at any given time, and different combinations of signals tell the cells to go down different pathways.

What's the difference in response time between changing gene expression and modifying protein function?

Changing gene expression takes longer (minutes to hours) than modifying protein function (seconds to minutes).

What is the function of intracellular cascades/signaling pathways?

They relay the signal from the activated receptor to various proteins inside the cell, ultimately leading to a biological response.

At a high level, how does signal transduction work?

A signal molecule (ligand) binds to a receptor, initiating a relay of signals through various proteins and secondary messengers, leading to an integrated response and feedback mechanisms.

What is positive feedback in cell signaling?

Feedback from the end of the signaling pathway tells a step earlier in the pathway to amplify the signal and keep it going.

What is negative feedback in cell signaling?

Feedback from the end of the signaling pathway tells a step earlier in the pathway to reduce or stop the signal.

What are molecular switches, and what are the two broad categories?

Mechanisms to turn a protein on or off. Two categories: phosphorylation-based and GTP-binding protein-based.

How does phosphorylation act as a molecular switch?

A kinase phosphorylates a protein, generally turning it on, while a phosphatase removes the phosphate group, turning it off.

How do GTP-binding proteins act as molecular switches?

When bound to GTP, the protein is active; when it hydrolyzes GTP to GDP, it becomes inactive until GDP is replaced with GTP.

What is the function of a GAP (GTPase-activating protein)?

A GAP causes the dissociation of GDP to inactivate a GTP-binding protein.

What is the function of a GEF (guanine nucleotide exchange factor)?

A GEF causes association of GTP to activate a GTP-binding protein.

What are the three main types of cell-surface receptors?

Ion channel receptors, G protein-coupled receptors (GPCRs), and enzyme-coupled receptors.

How do ion channel receptors work?

A signal molecule binds to the ion channel, opens it up, and allows ions to flow across the membrane, causing a signal to progress.

What are G protein-coupled receptors (GPCRs)?

Receptors with seven transmembrane loops that are associated with a trimeric G protein, which initiates signal transduction upon activation.

What are the three parts of a trimeric G protein?

Alpha, beta, and gamma subunits.

How do enzyme-coupled receptors function?

They typically function as dimers; when a signal molecule binds, it causes dimerization, activating the receptor and initiating signal transduction.

Describe G protein activation

Signal molecule binds to the GPCR, causing GDP to dissociate, and then GTP binds to the alpha subunit of the trimeric G protein. The alpha subunit is activated and the beta gamma subunits together are activated.

What are secondary messengers?

Small molecules that can travel through the cell to expand or diversify the signal and the signal transduction pathway.

Give me an example of a secondary messenger.

Cyclic AMP (cAMP).

How does cyclic AMP (cAMP) function?

It can bind to protein kinase A (PKA), causing it to phosphorylate downstream targets.

How do G protein-coupled receptors activate phospholipids?

The activated G protein can turn on phospholipase C, which cuts off the top of phosphorylated inositol phospholipid, creating IP3 and diacylglycerol.

What is phosphatidylinositol?

Molecule inside the inner leaflet of the plasma membrane.

What is the role of IP3 (inositol triphosphate)?

It can travel into the cell, bind to an ion channel, and cause the release of calcium into the cytoplasm.

What is the role of diacylglycerol?

It remains in the plasma membrane and can bind to protein kinase C.

What is the role of calcium in signaling?

It acts as a secondary messenger, can bind to calmodulin, and can interact with different kinases, turning them on. It also binds to phosphokinase c that's bound itself to the diacylglycerol.

What is receptor tyrosine kinase and what happens when a signal binds?

An enzyme-linked receptor that, upon signal binding, dimerizes and phosphorylates tyrosine residues on each other, creating docking sites for other proteins.

What is the role of SH2 domains?

Recognize phosphorylated tyrosines and bind and then can signal downstream.

What is RAS?

A monomeric G protein that is associated with receptor tyrosine kinases and functions similarly to the G proteins in nuclear transport.