Cell Bio Lec 8

In the second major means of intercellular communication the signal is transmitted by

regulatory chemical messengers

Multicellular organisms can control the activities of specialized cells through release

release of chemical messengers

SIgnal Molecule- require physical contact between sending and receiving cells

Juxtacrine signals

Signal molecule-act on the same cell that produces them

Autocrine signals

signal molecule- are produced far from the target tissues, which they reach via the circulatory system

Endocrine signals

signal molecule- are diffusible and act over a short range

paracrine signals

what is a ligand?

A ligand is a messenger molecule that binds to a specific receptor on or inside a target cell.

What happens when a messenger reaches its target cell?

It binds to a receptor through the receptor's binding site (binding pocket), allowing the cell to receive and respond to the signal.

What is the first step in cell-cell signaling?

Ligand binding to a receptor on the target cell.

What are second messengers?

Molecules or ions produced inside the cell after ligand binding that help transmit the signal.

What happens after second messengers are produced?

They trigger a cascade of changes inside the receiving cell.

The process by which a cell responds to ligand-receptor binding by changing its behavior or gene expression is?

SIgnal transduction

The process by which a cell responds to ligand-receptor binding by changing its behavior or gene expression.

The cell's behavior or gene expression.

The multiplication of a signal's effect during a signal transduction pathway, where each step activates many more molecules is?

Signal amplification

Give an example of signal amplification.

One epinephrine molecule can trigger the breakdown of glycogen in liver cells, leading to the release of hundreds of millions of glucose molecules

Ligands that bind the receptor are?

Examples:

• proteins (insulin)
• Peptides (glucagon)
• Amino acids and their derivatives (epinephrine)

First messengers

Molecules that relay signals in cell to initiate cascade of changes are?

– Ions or small molecules
– Examples

cAMP, fatty acids, lipids (IP3 and Dag), ions (CA2+)

Second messengers

Receptor types

Ligand-gated channels

Plasma membrane receptors

• G protein receptors

• protein kinase-associated receptors

Steroid hormone receptos

• bound by hydrophobic messengers (steroid hormones)- nuclear receptors)

What happens when a ligand binds a G protein-linked receptor

Ligand binding activates a G protein (guanine nucleotide-binding protein), which then binds to a target protein and alters its activity.

What are the structural features of a G protein-linked receptor?

t has 7 transmembrane α-helices, extracellular loops that bind ligands, and intracellular loops that interact with G proteins.