Cell Communication Flashcards
Cell-to cell communication importance
Critical for the function and survival of cells. Responsible for the growth and development of multicellular organisms
Three ways cells communicate
- Direct contact
- Local signaling
- Long-distance signaling
Direct contact
Communication through cell junctions, signaling substances and other material in the cytoplasm can pass freely between adjacent cells
Animal cells: Gap junctions
Plant cells: Plasmodesmata
Local regulators/signaling
- Secreting cell releases chemical messages that travel a short distance through the extracellular fluid
- Chemical messages will cause a response in a target cell
Paracrine signaling
Secretory cells release local regulators (growth factors) via exocytosis to an adjacent cell
Synaptic signaling
Occurs in animal nervous systems
1. Neurons secrete neurotransmitters
2. Diffuse across the synaptic cleft-space between the nerve and target cell
Long Distance signaling
-Animals and plants use hormones for this type of signaling
Plants: Release hormones that travel in the plants (xylem or phloem) or through the air to reach target tissues
Animals: Endocrine signaling. Specialized cells release hormones into the circulatory system where they reach target cells
Insulin as an example of endocrine signaling
Released from the pancreas into the bloodstream where it circulates through the body and binds to target cells
Cell messaging three stages
- Reception
- Transduction
- Response
Reception Overview
The detection and receiving of a ligand by a receptor in a target cell
Receptor definition
Macromolecule that binds to a signal molecule (ligand)
Receptor interaction
- All receptors have an area that interacts with the ligand and an area that transmits a signal to another protein
*Binding between ligand and receptor is highly specific
Steps of reception
- When the ligand binds to the receptor, the receptor activates via a conformational change
- This allows the receptor to initiate a transduction signal
Ligand
Molecule that binds to another (usually larger) molecule
Where are receptors located?
Plasma membrane or intracellular
Plasma membrane receptors
-Most common type of receptor
-Binds to receptors that are polar(water soluble, large)
Examples: G protein coupled receptors, ligand-gated ion channels
Intracellular receptors
-Found in cytoplasm or nucleus of target cell
-Binds to ligands that can pass through the plasma membrane (hydrophobic molecules, steroid and thyroid hormones, gasses like nitric oxide)
Transduction overview
The conversion of an extracellular signal to an intracellular signal that will bring about a cellular response
What does transduction require?
A sequence of changes in a series of molecules known as the signal transduction pathway
Signal transduction pathway and protein activity
Regulates protein activity through phosphorylation and dephosphorylation
Kinase
Phosphorylation, turns on the process, relays signal inside cell
Phosphotase
Dephosphorylation, shuts off pathways
During transduction a signal is…
Amplified
Second messengers
Small, non-protein molecules help relay the message and amplify the message and response.
*Cyclic AMP common 2nd messenger
Response overview
The final molecule in the signaling pathway converts the signal to a response that will alter a cellular process
Three examples of responses:
- Protein that can alter membrane permeability
- Enzyme that will change a metabolic process
- Protein that turns genes on or off
Signal transduction pathways
*Can influence how a cell responds to it’s environment
*Can result in changes in gene expression and cell function, alter phenotypes or result in cell death
Changes in signal transduction pathways
-mutations to receptor or to any component of the signaling pathway will result in a change to the transduction of the signal
Two categories of cell membrane receptors
1.G protein coupled receptors (GPCR’s)
2. Ion channels
G protein coupled receptors overview
-Largest category of cell surface receptors
-Important in animal sensory systems
-Binds to a G protein, GTP, which is an energy molecule similar to ATP
-The GPCR, enzyme, and G protein are inactive until a ligand binds to GPCR on the extracellular side
What does ligand bonding cause in GPCR’s
- Causes cytoplasmic side to change shape
- Allows for the G protein to bind to GPCR
*Activates the GPCR and G protein
*GDP becomes GTP - Part of the activated G protein can then bind to the enzyme
*Activate enzyme, amplifies signal and leads to a cellular response
Ion channels location and importance
- Plasma membrane
- Important in the nervous system
Ion channels overview
- Receptors that act as a “gate for ions”
- When a ligand bonds to the receptor the “gate” opens or closes allowing the diffusion of specific ions
- This initiates a series of events that lead to a cellular response
