U2 Chapter 11: Cell Communication Flashcards
Signal Transduction Pathways
Involves the binding of extracellular signaling molecules and ligands to receptors located on the cell surface or inside the cell that trigger events inside the cell, to invoke a response. The response can then alter the cell’s metabolism, shape, and gene expression
Quorum Sensing
Related to signal transduction pathways, helps bacterial cells sense the local density of bacterial cells
Hormones
The body’s chemical messengers, sending signals into the bloodstream and tissues. Hormones work slowly, over time, and affect many different processes, including growth and development, metabolism
- long-distance signaling
Local Regulators
Chemical signals that travel over short distances by diffusion, help regulate blood pressure, nervous system function, and reproduction
- local signaling involves short distance signaling, either direct contact or the secretion of local regulators
Three-stage Cell Signaling Pathway
Triggered by hormones like epinephrine (used for allergic reactions (including anaphylaxis) to insect bites or stings, medicines, foods, or other substances)
1) signal reception: receptor and signaling molecule
2) signal transduction: relay molecules 1, 2, 3
3) cellular response
Ligand
Signaling molecule that irreversibly binds to a receiving protein molecule, otherwise known as a receptor
- highly specific shape, receptor is often the initial transduction of the signal
GPCRs: Cell-surface Transmembrane Receptors
G protein-coupled receptors, works with cytoplasmic G proteins
- ligand binding activates the receptor, which then activates a specific G protein, which activates another protein, thus propagating the signal
RTKs: Cell-surface Transmembrane Receptors
Receptor tyrosine kinases, reacts to the binding of signaling molecules by forming dimers and then adding phosphate groups to tyrosine on the cytoplasmic part of the other monomer making up the dimer
- relay proteins in the cell can then be activated by binding to different phosphorylated tyrosine, allowing this receptor to trigger several pathways at once
Ligand-gated Ion Channels: Cell-surface Transmembrane Receptors
Open or close in response to binding by specific signaling molecules, regulating the flow of specific ions across the membrane
Phosphorylation Cascades
Series of protein kinases each add a phosphate group to the next one in line, activating it
- (enzymes) protein phosphatases remove the phosphate groups
- balance between phosphorylation and dephosphorylation regulates the activity of proteins involved in the sequential steps of a signal transduction pathway
Cyclic AMP (cAMP)
Second messengers (along with ion Ca2+) diffuse readily through the cytosol and thus help broadcast signals quickly
Adenylyl Cyclase
Activated (usually) by G proteins, thus makes cAMP from ATP
Tyrosine Kinase Pathway (RTKs)
A group of membrane-bound receptors that play an important role in the normal function of cells. They act as signal transducers that mediate cell-to-cell communication by phosphorylating tyrosine residues on key intracellular substrate proteins
- second messengers: diacylglycerol (DAG) and inositol triphosphate (IP3) => trigger a subsequent increase in CA2+ levels
Scaffolding Proteins
Increases signaling efficiency, brings together two or more proteins in a relatively stable configuration
Pathway Branching
Helps the cell coordinate signals and responses
