topics 1,2,3,4 unit 4

what is cell communication critical for?

the function and survival of cells

what is cell communication responsible for?

the growth and development of multicellular organisms

How do cells communicate?

direct contact, local signaling, long-distance signaling

How does Direct contact occur?

cell junctions (animals) or plasmodesmata (plant cells)

signaling substances and other material dissolved in the cytoplasm can pass freely between adjacent cells

Direct contact

a secreting cell will release chemical messages (local regulators/ligands) that travel a short distance through the extracellular fluid

local regulators

What are two examples of Local regulators?

Paracrine and Synaptic

secretory cells release local regulators (ie. growth factors) via exocytosis to an adjacent cell

paracrine signaling

occurs in an animal nervous system; neurons secrete neurotransmitters

synaptic signaling

What do plant and animals use for long distance signaling?

Hormones

How do plants use hormones for long distance signaling?

they release hormones that travel in the plant vascular tissue or through the air to reach the target tissues

How do animals use hormones for long distance signaling?

specialized cells release hormones into the circulatory system where they reach target cells

What are the three stages of cell signaling?

Reception, Transduction, Response

What is reception?

the detection and receiving of a ligand by a receptor in the target cell; when the ligand binds to the receptor, the receptor activates, intiating the transduction signal.

Receptor

macromolecule that binds to a signal molecule (ligand); all have an area that interacts with the ligand and an area that transmits a signal to another protein; binding is highly specific

Plasma membrane receptors

a most common type of receptor; binds to ligands that are polar, water-soluble, and large

Intracellular receptors

found in the cytoplasm or the nucleus of the target cell; bind to the ligands that can pass through the plasma membrane (ie. hydrophobic molecules, steroid and thyroid hormones, and gasses)

What is transduction?

the conversion of an extracellular signal to and intracellular signal that will bring about a cellular response; requires a sequence of changes in a series of molecules known as signal transduction pathway.

How does the signal transduction pathway regulate protein activity?

phosphorylation by the enzyme protein kinase; relays signal inside the cell; dephosphorylation by the enzyme protein phosphatase; shutting off pathways

Which stage is the signal amplified?

Transduction

Second messengers:

small, non-protein molecules and ions help relay the message and amplify the response

What is response?

the final molecules in the signaling pathway converts the signal to a response that will alter a cellular process.

What kind of changes do signal transduction pathways result in?

gene expression and cell function which can cause cell death

What will result in a chance to the transduction of a signal?

mutations to receptor proteins or to any component of the signaling pathway

What are the two main categories of cell membrane receptors?

G-protein coupled receptors and ion channels

What are GPCRS?

the largest category of cell surface receptors, important in animal sensory systems, binds to a G protein that can bind to GTP, which is an energy molecule similar to ATP

What does the ligand binding cause the cytoplasmic side to do?

change shape

What are ligand gated ion channels?

Located in the plasma membrane; important in the nervous system; act as a gate for ions.