Chapter 9 — Cell Communication

What is cell signaling?

Communication between cells using chemical signals

What are the four types of cell signaling?

Paracrine endocrine autocrine and direct signaling

What is paracrine signaling?

Signals diffuse to nearby cells

What is endocrine signaling?

Hormones travel through the bloodstream to distant targets

What is autocrine signaling?

A cell releases a signal that can bind to itself

What is direct signaling through gap junctions?

Small signaling molecules pass directly between connected cells

What is a ligand?

A signaling molecule that binds to a receptor

What is a receptor?

A protein or molecule that binds a signal and initiates a response

How do hormones differ from neurotransmitters?

Hormones travel through blood and often act longer while neurotransmitters act rapidly near neurons

What is the endocrine system?

Cells and glands that secrete hormones into the bloodstream

What are the three main classes of hormones?

Amino acid derivatives polypeptides and steroids

How do steroid hormones enter cells?

They pass through the membrane because they are hydrophobic and nonpolar

How do polypeptide hormones signal?

They bind to cell-surface receptors and activate signaling pathways

What is signal transduction?

The process of transmitting a signal from a receptor into a cell

What is a second messenger?

An intracellular molecule that relays a signal inside the cell such as cAMP

What does cAMP do in epinephrine signaling?

It acts as a second messenger that activates protein kinase A (PKA)

What is epinephrine's fight-or-flight role?

It quickly increases glucose availability for energy during danger

What does insulin stimulate?

Glucose uptake by cells

What is an agonist?

A substance that activates a receptor or increases its activity

What is an antagonist?

A substance that blocks a receptor or prevents a signaling action

How does botulinum toxin affect acetylcholine?

It prevents acetylcholine release potentially causing muscle paralysis

How does black widow spider venom affect acetylcholine?

It increases acetylcholine release causing muscle cramps and spasms

What do antihistamines do?

They block histamine receptors and reduce allergy symptoms

What is a signaling pathway?

A sequence of molecular events following ligand binding to a receptor

What is signal integration?

Signals from different receptors combine to produce a cellular response

What is apoptosis?

Programmed cell death that removes unneeded or damaged cells

How are signals terminated?

Signals may be degraded or proteins deactivated by phosphatases

What is quorum sensing in bacteria?

Cell communication using autoinducers to respond to population density

What is dimerization?

Two receptors join to form a stable complex

Why can abnormal EGFR signaling be dangerous?

It can cause uncontrolled cell growth and contribute to cance