cell communication

direct communication

occurs when cells transmit signals to each other through cytoplasm of two adjacent cells via channels

direct communication for animal cells

gap junctions (connexons)

direct communication for plant cells

plasmodesmata

cell-cell recognition

complementary cell-surface molecules between adjacent cells can interact and bind to each other

example for cell-cell recognition

receptor/antigen interaction in immune system

types of local signaling

paracrine, synaptic, autocrine

paracrine signaling

a signaling cell will release chemical messages that travel a short distance through the extracellular fluid and cause a response in a nearby target cell

example of paracrine signaling

allergens- histamine signal for inflammatory response in nearby cells

synaptic signaling

occurs in animal nervous systems (special type of paracrine signaling)-nervous secrete neurotransmitters that diffuse across the synaptic cleft and bind to receptors causing a chemical change inside the cell.

autocrine signaling

a cells signals to itself - release a ligand that binds to receptors on the same cell to initiate signaling

-allow cell to regulate itself through positive and negative feedback

example of autocrine signaling

macrophage cells release cytokines that can signal to the macrophage itself to regulate activity 

long distance signaling

animals and plants use hormones to produce a response in target cells that may be far from the signaling cell

long distance in plants

release hormones that travel in the plant vascular tissue (xylem and phloem) or through the air to reach target tissues

long distance in animals

use endocrine system - release hormones ino the circulatory system where they reach target cells- insulin

cell signaling

begins wiht an nteraction between a ligand and receptor

ligand

chemical messenger - protein or small molecules

receptor

proteins that recognize and bind to specific chemical messengers

binding initiates

signaling cascades

receptor ligand binding is

highly specific

receptors are found

plasma membrane- surface receptors

inside- cytoplasm or nucleus

surface cell receptors bind to

ligands that are polar, water-soluble, large

ex- g protein coupled with receptors

ligand-gated ion channels

number of domains surface receptors have

3-

ligand binding

transmembrane

intracellular

ligand binding domain

area that interacts with the ligand

transmembrane domain

hydrophobic region that spabs the plasma membrane

intracellular domain

region inside the cell that transmits a signal

intracellular receptors

found in cytoplasm or nucleus of target cell

bind to ligands that pass through plasma membrane

function as transcriptopn factors

number of intracellular receptors domains

2

domains of intracellular receptors

ligand and dna binding domain- (interact with target gene)

three stages of cell to cell signaling

reception

transduction

response

reception of cell to cell signaling

ligand binds to receptor

transduction of cell to cell signaling

extracellular signal is converted into an intracellular response

response of cell to cell signaling

a cell process is altered

steps of intracellular responses

reception

transduction

response

reception in intracellular receptors

ligand diffuses across plasma membrane and binds to intracellular receptor

transduction in intracellular receptors

causes dna binding domain of receptor to change (activate)

response intracellular receptors

the ligand receptor complex can now bind to control regions of target genes in the nucleus- turn on or off genes

cell activity altered

stages of cell surface receptors

reception

transduction (long)

response

reception in cell surface receptors

ligand binds to specific cell receptor on target cell and can be polar or large

transduction in cell surface receptors

The activated receptor initiates a cascade of molecular events inside the cell. This often involves a relay of signaling molecules and second messengers that convert the signal into a form the cell can act upon, often amplifying it in the process.

response in cell surface

final molecule i the signaling pathway converts the signal to a response that alter process- cell growth, secretion of molecules, genes off or on

cross talk

paths aren’t straighforward

cross talk in protein kinase

phosphorylate proteins in another pathway

cross talk in gene transcription

requires 2 signals sometimes