Cellular Communication

Paracrine signaling

Local signaling in animal cells involving secreted messengers that travel short distances

Synaptic signaling

a type of paracrine signaling that occurs in the nervous system, where an electric signal triggers the release of a neurotransmitter

Hormonal/endocrine signaling

long distance signaling where hormones travel through the bloodstream to their target cells

3 steps of cell signaling

Signal reception, signal transduction, cellular response

signal reception

the cell detects a signaling molecule (acting as a ligand) and it binds to a receptor protein on the surface

signal transduction

the binding of the signaling molecule alters the receptor and initiates a signal transduction pathway

cellular response

the transduced signal triggers a
specific response in the target cell

G protein-coupled receptors (GPCRs)

cell-surface transmembrane receptors that work with the help of a G protein

how GPCRs work

G proteins bind GTP from GDP, and then trigger a cellular response

Receptor tyrosine kinases (RTKs)

membrane receptors that catalyze the transfer of phosphate
groups from A T P to another protein

Protein kinases

proteins that transfer phosphates from A T P to protein, a process called phosphorylation

Phosphorylation cascade

a chain of phosphorylation reactions involving kinases that greatly amplifies a signal with each step

protein phosphotase

proteins that dephosphorylate other proteins. important in shutting down the phosphorylation cascade by inactivating protein kinases

second messengers

small nonpolar nonproteins that enter a cell via diffusion and act as another messenger to transmit a signal

Cyclic AMP (monophosphate)

a widely used second messenger created by removing two phosphates from ATP
usually activates protein kinase A anf is often associated with GPCRs

Adenylyl cyclase

an enzyme in the plasma membrane that converts ATP to cAMP in response to an extracellular signal

calcium ions (ca2+)

a widely used second messenger due to its conc inside the cell being very low, meaning a small change greatly affects the conc greatly

aspects of signal regulation

amplication of signal and response, specificity of response, efficiency of response, termination of signal

signal amplicfication

signal cascade amplifies the cell response and the number of products that can be made

signal specificity and response coordination

different proteins in different cells can cause a completely different affect for the same signal

cross talk

two pathways "communicate" via activation or inhibition

signal efficiency

scaffolding proteins are used to make the signal more efficient

scaffolding

large relay proteins to
which several other relay proteins are attached.
they increase the signal transduction efficiency by grouping togetherdifferent proteins involved in the same pathway

signal termination

uses inactivation mechanisms like unbound receptors due to a lack of signaling molecules

apoptosis

a type of programmed cell death that packages parts of the cell to be digested by scavenger cells. prevents enzyme leaking that could damage other cells
can be triggered by inner or outer signals