Chapter 07: Cell Communication and Multicellularity

Flashcards covering key concepts from Chapter 07: Cell Communication and Multicellularity (Life: The Science of Biology, 12e).

What are the three main stages of cell signaling?

Reception → Transduction → Response.

Define paracrine signaling.

Signals affect nearby cells.

Define juxtacrine signaling.

Signals affect adjacent cells.

Define autocrine signaling.

Signals affect the cells that produced them.

What is endocrine signaling?

Circulating hormones transported by the circulatory system to distant target cells.

Where are receptors located for hydrophobic vs hydrophilic signals?

Hydrophobic signals use cytoplasmic/intracellular receptors; hydrophilic signals use plasma membrane receptors.

How does a signaling molecule affect receptor conformation?

Binding causes the receptor to change shape, initiating downstream signaling.

Give an example of a lipid-soluble hormone that uses intracellular receptors.

Estrogen (a steroid hormone).

Name the three major classes of plasma membrane receptors.

Ion channels, Protein kinase receptors, G protein-coupled receptors.

What is a gated ion channel?

A channel that opens or closes in response to a signal, allowing ions to pass; example: acetylcholine receptor.

Describe the G protein cycle in GPCR signaling.

Ligand binding activates receptor; G protein exchanges GDP for GTP; activated G protein subunit activates an effector; GTP is hydrolyzed to GDP to turn off.

What are second messengers?

Small diffusible molecules that relay signals from membrane receptors to intracellular targets.

Name two primary second messengers produced by GPCR signaling.

cAMP (from ATP via adenylyl cyclase) and Ca2+.

What are IP3 and DAG, and how are they produced?

Derived from PIP2 by phospholipase C; IP3 diffuses to cytoplasm; DAG remains in the membrane; both activate PKC.

How does calcium function as a second messenger?

Ca2+ rises in the cytoplasm and binds to calmodulin, activating enzymes.

What is a protein kinase cascade?

A signaling pathway where sequential protein kinases phosphorylate each other, amplifying the signal.

What is Ras, and why is it important in cancer?

A monomeric G protein downstream of RTKs; mutations that lock Ras in the GTP-bound active form are found in ~30% of tumors.

What is a receptor tyrosine kinase (RTK) activation mechanism?

Ligand binding induces receptor dimerization and autophosphorylation.

Give an insulin receptor as an example.

An example of a receptor tyrosine kinase that autophosphorylates and triggers downstream signaling.

What is a GPCR effector?

A target protein activated by the G protein, leading to downstream effects.

Why are signaling pathways advantageous over direct activation?

They allow integration of signals, multiple targets, and amplification of the response.

Describe the olfactory receptor signaling example.

Odorant binding to a receptor opens ion channels in sensory neurons; each neuron expresses one receptor from ~950 genes.

What is the epinephrine signaling pathway in liver cells?

Epinephrine binds GPCR → G protein activates adenylyl cyclase → increased cAMP → kinases → glycogen breakdown; glycogen synthase inhibited; glycogen phosphorylase activated.

What is feedback regulation in signaling?

Enzymes that activate transducers and enzymes that inactivate them balance the cellular response.

What is amplification in signal transduction?

The signal is amplified at each step, producing a large response from a small initial signal.

What is the role of calmodulin?

A calcium-binding protein that activates certain enzymes when Ca2+ binds.

What is the basic flow of cellular signaling?

Reception → Transduction → Response.