Chapter 9 - Cell Communication

local signaling is like

talking to your neighbor

long distance signaling is like

talking on the phone to someone a couple states away

two ways the cells communicate

local signaling & long distance pathways

types of local signaling

paracrine signaling & synaptic signaling

paracrine signaling

acts on nearby target cells by secreting molecules of a local regulator

synaptic signaling

a nerve cell releases a neurotransmitter molecule into a synapse, stimulating the target cell

how does long distance signaling work

chemicals must travel longer distances to reach their target cell - hormones secreted by the endocrine system

how do the hormones travel for long distance pathways

they get on the highway (vascular system)

which of the following is characterized by a cell releasing a signal molecule into the environment, followed by a number of cells in the immediate vicinity responding?

paracrine signaling

who suggested the three stages of cell signaling by looking at epinephrine

earl w. sutherland

what are the stages of cell signaling

reception, transduction, response

reception

target cells detection of a signaling molecule coming from outside the cell

ligand

a molecule that specifically bonds to another molecule (bonds to the receptor)

what is the example of how a receptor works

the wide receiver caught the ball way up in the air, but then brought it down and tucked it in

how do receptors work

a message was sent, and it changed that receptor in some way

g-protein coupled receptors (GPCRs)

work with the help of a G protein, a protein that binds energy rich molecule GTP (guanine triphosphate)

what do GPCRs play a role in

embryonic development and sensory reception (vision and smell depend on these receptors)

how does transduction work

it propagates and amplifies the message to pass it along

how does response work

it is a response to the message that was sent

ligand-gated ion channel receptor

a type of membrane receptor that can act as a “gate” when the receptor changes shape

how does the ligand-gated ion channel receptor work

has “doors” that are closed, but when the signaling molecule binds, the “doors” open which allows for ions to enter the membrane. Once the cellular response has occurred, the doors close back up

ligand-gated ion channel receptors are important in

the nervous system - neurotransmitter molecules released at the synapse between two nerve cells

receptor tyrosine kinases (RTKs)

belong to a major class of plasma membrane receptors characterized by having enzymatic activity

what does “kinase” tell you

it has the ability to go through phosphorylation (add phosphate groups)

how do RTKs work

two RTKs get signaling molecules and are pulled together into a dimer and then phosphates are added to trigger relay molecules to eventually lead to cellular response

what do RTKs do

help the cell regulate and coordinate many aspects of cell growth and cell reproduction

intracellular receptors

proteins are found either in the cytoplasm of nucleus of target cells

one of the major categories of receptors in the plasma membrane reacts by forming dimers, adding phosphate groups, then activating relay proteins. which type does this?

receptor tyrosine kinases

transduction

a cascade of molecular interactions relays signals from receptors to target molecules in the cell

protein kinase

transfers a phosphate from an ATP to a protein (phosphorylation)

protein phosphatases

enzymes that can rapidly remove phosphate groups from proteins (dephosphorylation)

second messengers

small molecules and ions that start transduction, spreading quickly through diffusion

cyclic AMP (cAMP)

a second messenger made from ATP by adenylyl cyclase

calcium ions and inositol triphosphate (IP₃)

lead to the release of calcium that aids in releasing neurotransmitters, growth factors, and some hormones

consider this pathway: epinephrine - g-protein coupled receptor - g protein - adenylyl cyclase - cAMP. Identify the second messenger.

cAMP

response

cell signaling leads to the regulation of transcription or cytoplasmic activities

fine tuning of the response

the specificity of the cell signaling and coordination of the response

signaling efficiency

scaffolding proteins and signaling complexes - the arrangement facilitates signal transduction

apoptosis

pre-programmed cell death, most elaborate way

blebbing

part of apoptosis where the cell forms into vesicles; without it, all cellular content would leak and could be harmful to neighboring cells

scavenger cells

specialized cells that engulf and digest the blebbing to protect neighboring cells

what does apoptosis play a role in

plays an important role in embryonic development, such as in C. Elegans - occurs exactly 131 times within this organism during development

how is apoptosis regulated

by genes such as ced 3, ced 4, and ced 9 (in the mitochondria)

role of apoptosis in vertebrate development

important in development and maintenance, such as the formation of fingers (apoptosis breaks down interdigital tissue which changes the pad into fingers)

what could webbing in between fingers and toes mean

failure of signaling molecules to signal for apoptosis

phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because

they amplify the original signal many fold

apoptosis involves all but which of the following?

lysis of the cell

receptors for signal molecules…

may be found embedded in the plasma membrane, or found within the cytoplasm or nucleus

when a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

signal molecule