C2.1 Chemical signalling

Vocabulary flashcards related to cell signaling.

Chemical Signalling

Method of communication between cells where the signalling cell releases signalling molecules (ligands) that interact with receptors (proteins) in a target cell.

Ligands

Signalling molecules released from a signalling cell that interact with receptors in a target cell.

Quorum Sensing (QS)

Bacterial cell-cell communication process that involves the production, detection, and response to extracellular signalling molecules called autoinducers.

Autoinducers

Extracellular signaling molecules involved in quorum sensing that accumulate as bacterial population density increases.

Vibrio fischeri

Aquatic bacterium that secretes an autoinducer which binds to the LuxR receptor to express genes coding for luciferase, enabling bioluminescence.

Luciferase

Enzyme that catalyzes an oxidation reaction that releases energy as blue/green light, utilized by Vibrio fischeri for bioluminescence.

Hormones

Chemical signals produced and secreted in small quantities by glands, transported in the bloodstream to target cells to regulate processes; often have widespread effects.

Neurotransmitters

Chemical signals secreted by the presynaptic neuron that travel through the synaptic cleft to be received by the postsynaptic neuron to stimulate or inhibit nerve impulse; have localized and specific effects.

Cytokines

Small proteins that act on the single cell that produced them, or nearby ones, involved in immune responses and inflammation; work by binding to receptors on the membrane.

Calcium ions

Involved in chemical signalling within muscle fibers and neurons. During initiation of muscle contraction, an influx of calcium ions from the sarcoplasmic reticulum binds to troponin to expose the actin filaments and allow for muscle contraction to occur.

Intracellular receptors

Receptors found in the cytoplasm of the target cell that bind to hydrophobic signalling chemicals, altering gene expression.

Hydrophobic ligands

Hydrophobic signalling chemicals, such as steroid hormones, that bind to intracellular receptors.

Extracellular receptors

Transmembrane proteins found within the target cell’s plasma membrane that bind to hydrophilic ligands from outside the cell.

Hydrophilic ligands

Hydrophilic ligands that are unable to pass through the hydrophobic core of the plasma membrane and bind to extracellular receptors.

Signal transduction

Sequence of responses within a cell from receiving a signal to changes in activity and behavior.

G-protein-coupled receptors (GPCRs)

Transmembrane proteins associated with a G-protein on the cytoplasmic side that initiate cell responses upon ligand stimulation.

G-proteins

Proteins that bind to guanine nucleotides GTP and GDP, involved in G-protein-coupled receptor signalling.

Adenylyl cyclase

Enzyme activated by G-proteins that catalyzes the conversion of ATP to cAMP.

Cyclic AMP (cAMP)

Secondary messenger produced by adenylyl cyclase that activates protein kinase.

Protein kinase

Enzyme in the cytosol activated by cAMP that initiates a phosphorylation cascade.

Tyrosine kinase receptor

Receptors in the plasma membrane that, upon insulin binding, cause phosphorylation of tyrosine inside the cell, leading to the movement of vesicles containing glucose transporters to the plasma membrane.

Kinase

Enzyme that transfers phosphate groups from ATP to a protein.

Ion-channel-coupled receptors

Receptors where ligand binding causes a conformational change, opening an ion channel that allows positively charged ions to pass through, changing the voltage across the plasma membrane.

Oestradiol

Hormone that diffuses into cells of the hypothalamus, enhancing the transcription of GnRH mRNA, involved in the release of gonadotropins FSH and LH.

Progesterone

Hormone that diffuses into uterine cells and enhances the transcription of genes involved in the maintenance of the endometrial lining.

Positive feedback signalling pathways

Signalling pathways where the end product amplifies the starting point, creating more of the product.

Negative feedback signalling pathways

Signalling pathways where a rise in the end product inhibits the starting point, bringing levels back to normal.