BIOL 2311 Chapter 9 (Cell Communication)

3 Steps of signal processing

reception, transduction, response

3 forms of cell communication

direct contact, local signaling, long-distance signaling

quorum sensing

way for bacteria to sense population density and adjust gene expression - bacteria release signal molecules in increasing concentration as cell density increases

sexual mating in yeast begins when:

one cell secretes a hormone that is recognized by a cell of a different sex

prior to evolution of multicellularity

mechanisms for cell signaling likely existed in unicellular organisms

protein pathway that evolved only after eukaryotes

protein kinase pathway and others

pathway conserved between fruit fly and humans

cell growth control pathway, at least 800 million years old

controlling cell

releases signal molecules to induce a response in other cells

reception

binding of a signal molecule with a specific receptor on a target cell

# of signal molecules a single receptor responds to

only one or very few

polar signal molecules

receptors are on cell surface, epinephrine

non polar signal molecules

receptors are within the cell, steroid hormones

transduction

changes a signal into a form that causes a cellular response, signaling cascade

response

specific cellular response to the received signal

2 forms of direct contact communication

direct linking of cytoplasms, cell-cell recognition

gap junction

direct cytoplasm link in animal cells

plasmodesmata

direct cytoplasm link in plant cells

cell-cell recognition

only in animal cells, specific membrane bound cell surface molecules interact to communicate

local signaling cell communication

a cell releases a signal molecule that diffuses through extracellular fluid to a cause a response in nearby target cells

local regulator

signal molecule that is released during local signaling

paracrine regulation

local signaling where the target cell is not the controlling cell

autocrine regulation

form of local signaling where the local regulator acts on the cell that produced it

local signaling of neurons

happens through chemical synapses, electrical signal in one cell triggers its release of neurotransmitters (local regulator)

long distance signaling

signaling molecule (hormone) triggers response in cell that is far from the controlling cell

long distance signaling in animals

hormones enter circulatory system to travel elsewhere in the body

long distance signaling in plants

most hormones travel through cells, some gaseous hormones travel through the air

most common means of cell communication

long distance signaling

3 components of cell communication using surface receptors

extracellular signal molecules, surface receptors, internal response pathways

what type of proteins are surface receptors

glycoproteins

surface receptors are transmembrane proteins

extends through cell membrane with binding site on outer membrane surface

when a signal molecule binds the receptor undergoes conformation changes

molecular structure is altered, signal is transmitted through plasma membrane and activates cytoplasmic end of the receptor

bacterial 2-component system includes:

surface receptor protein, intracellular response regulator

3 steps of bacterial 2-component signaling

1. a signaling molecule binds to and activates surface receptor

2. surface receptor phosphorylates and activates response regulator

3. response regulator binds to regulatory sequences in DNA, turning genes on or off