Cell Communication & Development - Week 1

Practice flashcards covering key concepts from Week 1: cell signaling, receptors, types of signaling, MAP kinase pathway, and examples.

What do all cells have that respond to signals from the environment?

Transmembrane receptors.

Development is the result of what kind of communication between cells?

Molecular communication.

How do unspecialized cells become specialized into many cell types?

Signals from the environment or nearby cells and a developmental program (pre-planned instructions).

What are gap junctions?

Intercellular connections made of a ring of proteins that transport ions and molecules between adjacent cells.

Name the four parts of cellular communication.

Signaling cell; signaling molecule (ligand); receptor protein; responding cell.

What is a signaling molecule (ligand) and what does it include?

A molecule that carries information from one cell to another when it binds to a receptor; includes peptides, lipids, and gases.

What is the receptor protein?

A molecule on the responding cell that binds the signaling molecule and interprets the signal.

What is the responding cell?

The cell that receives information from the signaling cell.

What are the four essential elements of cell signaling?

Receptor activation; signal transduction; cellular response; termination.

What is receptor activation?

The turning on of a receptor, often when the signaling molecule binds to it.

What is signal transduction?

A chain reaction where one molecule activates the next; pathway amplification.

What can the cellular response include?

Changes such as turning on genes that cause cells to divide; depends on the signal.

What is termination in signaling?

Stopping the cellular response to prevent overreaction and to allow new signals.

Define endocrine signaling.

Signaling over long distances via the bloodstream; examples: adrenaline, estradiol, testosterone.

Define paracrine signaling.

Over short distances (about 20 cell diameters); signaling molecules diffuse between cells; typically growth factors; water-soluble (polar).

Define autocrine signaling.

Signaling molecules released by a cell that bind to receptors on the same cell.

Define contact-dependent signaling.

Direct contact signaling where transmembrane proteins on adjacent cells act as signal and receptor; signaling molecule may remain membrane-bound.

What is ligand-binding site?

The specific site on a receptor where a signaling molecule binds; binding is noncovalent and requires compatibility.

Where are receptors for polar signaling molecules located?

On the cell surface; they are transmembrane proteins with extracellular, transmembrane, and cytoplasmic domains.

Where are receptors for nonpolar signaling molecules located?

Inside the cell (cytosol or nucleus) since nonpolar ligands can cross the membrane.

Name the three types of cell-surface receptors.

G protein-coupled receptors (GPCRs); receptor kinases; ion channels.

What is a G protein-coupled receptor (GPCR)?

A receptor that couples to G proteins and binds GTP and GDP; activates downstream signaling (e.g., PKA).

What is a receptor kinase?

A receptor that acts as an enzyme to add phosphate groups to substrates (phosphorylation), often via dimerization and autophosphorylation.

What is a kinase?

An enzyme that transfers a phosphate group from ATP to a substrate.

How is signaling terminated in receptor kinase pathways?

Phosphatases remove phosphate groups, inactivating proteins.

Describe the PDGF example of receptor kinase signaling in wound healing.

PDGF binds PDGF receptor kinases; receptors dimerize and transphosphorylate; recruited proteins (e.g., RAS) activate the MAP kinase cascade.

What is RAS's role in MAP kinase signaling?

Activated RAS (GTP-bound) triggers the kinase cascade; GDP-bound RAS is inactive.

What is the MAP kinase cascade?

A chain of protein kinases activated by phosphorylation; the final kinase enters the nucleus to phosphorylate transcription factors.

What is the effect of MAP kinase pathway activation on the cell?

Changes in gene expression, such as those promoting cell division.

What is signal amplification in kinase cascades?

A single signal activates many molecules of the next kinase, amplifying the response.

How is the MAPK pathway terminated?

Phosphatases deactivate receptor kinase and RAF/MEK/ERK; RAS hydrolyzes GTP to GDP.

How is receptor kinase signaling similar to GPCR signaling?

Both involve receptor activation, signal transduction, cellular response, and termination.

What is the difference between short-term and long-term cellular responses?

Short-term: seconds to minutes; modifies existing proteins. Long-term: hours to days; involves changes in gene expression.

Notch vs Delta: what makes Notch different?

Notch is the receptor; Delta is the ligand (signaling molecule).

If two signaling pathways are activated at the same time, what can happen?

They may inhibit each other, they may strengthen each other, or one may inhibit the other (cross-talk).