Exam 4

Cell communication

The process of cells detecting and responding to signals in the extracellular environment.

What are the two types of cell communication?

Intercellular signaling and Intracellular signaling

Intercellular signaling

communication between cells

Intracellular signaling

communication within cells

What are the different forms of signaling?

Autocrine, direct across gap junctions, paracrine, and endocrine

Autocrine

signaling cell and target cell can be the same.

Direct across gap junctions

channels that connect plasma membranes, allowing signaling molecules to pass from one cell to another.

Paracrine

Signals that act locally between cells

Endocrine

signals called hormones travel long distances between cells.

What are the different types of receptors?

Intracellular and cell-surface receptors

Intracellular receptors

found in the cytoplasm of the cell

cell-surface receptors

found on the cell surface and are integral proteins that bind to external ligand molecules.

what are the types of cell-surface receptors

enzyme-linked receptors and G-protein coupled receptors and ligand-gated ion channels

Enzyme-linked receptors

The extracellular domain binds the signal (ligand)

The intracellular domain becomes a catalyst that promotes a reaction.

G-protein-coupled-receptors

made of 7 transmembrane segments and activated receptors bind to G protein

Ligand-Gated ion channels

Ligand binding causes ion channels to open and ions flow through the membrane

What are the types of signaling molecules?

small hydrophobic ligands and water soluble ligands

small hydrophobic ligands

can directly diffuse through the plasma membrane and interact with intracellular receptors.

water-soluble ligands

polar; so they need help getting across the plasma membrane; mostly bind to cell-surface receptors

stage of cell signaling

receptor activation, signal transduction, cellular response

receptor activation

signaling molecules bind to the receptor

signal transduction

Once the ligand binds to the receptor, the signal is transmitted through the membrane into the cytoplasm

cellular response

Different responses possible could include a change in enzyme activity, altered function of structural proteins, changes in gene expression, cell growth, and cell death

signaling pathway

chain of events set off by the activated receptor

Signal Amplification

The binding of a signal to one receptor can cause the synthesis of many molecules that activate other proteins

speed

some signaling can propagate through the body in less than 20 seconds

Apoptosis

programmed cell death

Cell cycle

an ordered sequence of events involving cell growth and cell division

Genome

a cell’s DNA

In prokaryotes

single, circular double strand

In eukaryotes

multiple, linear double strands

Somatic cells

human body cells have