Studied by 23 people
Cell communication is responsible for what
Growth/development of multicellular organisms
Cell communicate through three general ways...
Direct contact, local signaling, and long distance signaling
direct contact
communication through cell junctions
In direct contact, signaling substances and other material dissolved in the cytoplasm can...
Pass freely between adjacent cells.
Direct contact, animals
gap junctions
Direct contact, plants
plasmodesmata
Example of direct contact
immune cells
local regulators
Secreting cell that will release chemical messages through extra cellular fluid
2 examples of local regulators?
Paracrine and synaptic
Paracrine signaling
Separatory cell releases messages (via Exocytosis) to adjacent cell
Synaptic signaling
in the animal nervous system; specialized type of local signaling
Neuron secretes neurotransmitters that diffuse across synaptic cleft
long distance signaling
plants and animals use chemicals called hormones
Plants long distance signaling
Release hormones I plant vascular tissue (xylem or pholem) or through air to reach target
Animal long distance signaling
Endocrine signaling:
Specialized cells release hormones into the blood stream ( circulatory system )
Insulin (example of long distance)
Released by pancreas into bloodstream where it circulates in the body
3 steps of cell-to-cell messaging
Reception, transduction, response
Reception
The target cell's detection of a signal molecule coming from outside the cell.
Receptor
protein that detects a signal molecule and performs an action in response
When a ligand binds to a receptor
The receptor undergoes a conformational change and activates
Receptors can be in the
Plasma membrane or intracellular fluid
Plasma membrane receptors
Large, polar, hydrophilic(most common in signaling pathways)
Intracellular receptors
small or nonpolar ligands can diffuse across the cell membrane
Intracellular receptor examples
Steroid/Hormone nuclear receptors
Gases
Example in intracellular receptors
Plasma membrane receptor examples
G protein, ligand gated ion channels
Transduction
The conversion Of an extra cellular signal to intracellular, signaling that will bring about a cellular response
What does transduction require.
a sequence of changes in a series of molecules known as a signal transduction pathway
How does the signal transduction pathway regulate protein
Phosphorylation by enzyme kinase
Depphosphorylation by phosphatase (shuts off pathways)
Relay signal inside cell
When is the signal amplified
Transduction
Second messengers
Small, non-protein water soluble molecules or ions that send messages throughout the cells by diffusion and amplify the response
What is the most common second messenger
cyclic AMP (cAMP)
Response
The final molecule in the signaling pathway will convert the signal to a response they will alter a cellular response.
Signal transduction pathways can influence
How a cell responses to its environment
How can signal transduction pathways change a cell
Change in gene expression and cell function which can alter phenotypes
What will changes in the signal transduction pathways lead to
Mutations to receptor proteins or to any component of the signaling pathways
What are the two main categories of cell membrane receptors (eukaryotes)
G protein coupled receptors (GPCRs) and Ion channels
GPCRs
Largest categories of cell surface receptors
Important for animal sensory systems
Binds to G protein that binds to GTP
GTP
energy molecules similar to ATP
Ligand binding causes...
Cytoplasmic side to change shape, allowing G protein to bind to GPCR and G protein GDP becomes GTP
When part of the activated G protein binds to the enzyme..
It activates the enzyme and amplifies the signal and leads to a cellular response
What are ion channels important in
Nervous system
Ligand gated ion channels
Receptors that act as a gate for ions
ligand hated ion channel acts..
When ligand binds to receptor, gate opens or closes allowing for the diffusion of specific ions (leads to cellular response )
Binding between ligand and receptor is
highly specific
