BIOL212 Ch11

Vocabulary practice flashcards covering cell signaling stages, membrane and intracellular receptors, transduction cascades, second messengers, and apoptosis from Campbell Biology Chapter 11.

Signal Transduction Pathway

A series of sequential molecular steps initiated by the binding of a specific signaling molecule to a cell-surface receptor that converts the signal into a specific cellular response.

Paracrine Signaling

A form of local signaling in animals where signaling cells secrete messenger molecules that travel only short distances to stimulate nearby target cells.

Growth Factors

A class of local animal regulators consisting of compounds that stimulate nearby target cells to grow and divide.

Synaptic Signaling

A specialized local signaling process occurring in the animal nervous system in which an electrical signal triggers the secretion of neurotransmitter molecules across a synapse to a target cell.

Hormones

Chemical messengers utilized by both plants and animals for long-distance signaling throughout the organism.

Endocrine Signaling

Long-distance hormonal signaling in animals where specialized cells release hormones that travel via the circulatory system to reach target cells.

Signal Reception

The initial stage of cell signaling in which a target cell detects an incoming signaling molecule as it binds to a specific receptor protein on the cell surface or inside the cell.

Signal Transduction

The second stage of cell signaling, wherein receptor binding alters the receptor protein and initiates a cascade of molecular interactions across relay molecules.

Cellular Response

The final stage of cell signaling (or output response), in which the transduced signal triggers a specific cellular activity, such as enzymatic activation or gene transcription.

Ligand

A signaling molecule that binds specifically to another molecule, typically a larger receptor protein, causing the receptor to undergo a change in shape.

G Protein-Coupled Receptor (GPCR)

A cell-surface transmembrane receptor that functions with the assistance of a G protein; GPCRs constitute the largest family of cell-surface receptors.

G Protein

A relay protein that binds the energy-rich molecule GTP and acts as an on/off molecular switch in cellular signaling pathways.

Receptor Tyrosine Kinase (RTK)

A membrane receptor characterized by enzymatic activity that catalyzes the transfer of phosphate groups from ATP to tyrosine residues on proteins, triggering multiple signal transduction pathways at once.

Ligand-Gated Ion Channel Receptor

A membrane receptor acting as a gate that opens or closes when the receptor changes shape upon ligand binding, allowing or blocking the flow of specific ions such as $Na^+$ or $Ca^{2+}$.

Intracellular Receptor

A receptor protein located in the cytoplasm or nucleus of target cells that binds small or hydrophobic chemical messengers capable of crossing the plasma membrane.

Transcription Factor

A special protein that controls gene expression by determining which specific genes are transcribed into mRNA; can be formed by activated hormone-receptor complexes.

Protein Kinase

An enzyme that transfers phosphate groups from ATP to a protein in a process known as phosphorylation.

Phosphorylation Cascade

A sequence of events in a signal transduction pathway where one protein kinase phosphorylates and activates another kinase, transmitting and amplifying the signal.

Protein Phosphatase

An enzyme that rapidly removes phosphate groups from proteins through dephosphorylation, functioning to turn off signal transduction pathways.

Second Messenger

A small, nonprotein, water-soluble molecule or ion that diffuses rapidly through the cytoplasm to relay a signal received by cell-surface receptors.

Cyclic AMP (cAMP)

A common second messenger made from ATP that typically acts in a signaling cascade by activating protein kinase A.

Adenylyl Cyclase

An enzyme embedded in the plasma membrane that converts ATP into cyclic AMP (cAMP) and pyrophosphate in response to an extracellular signal.

Inositol Trisphosphate ($IP_3$)

A second messenger generated by the cleavage of a membrane phospholipid that functions by opening ligand-gated calcium channels in the endoplasmic reticulum membrane.

Diacylglycerol (DAG)

A lipid second messenger produced in the plasma membrane alongside inositol trisphosphate ($IP_3$) through the cleavage of $PIP_2$ by phospholipase C.

Scaffolding Protein

A large relay protein to which several other relay proteins, such as protein kinases, are simultaneously bound, thereby increasing signal transduction speed and efficiency.

Cross-Talk

Interaction between two different signaling pathways within a cell, allowing one pathway to activate or inhibit components of the other to coordinate incoming signals.

Apoptosis

A form of programmed cell death wherein cellular components are chopped up and packaged into vesicles that are digested by scavenger cells, preventing damaging enzyme leakage.

Caspases

The primary proteases that execute apoptosis in mammals and other animals, consisting of approximately $15$ different enzymes involved in the death activation cascade.

Ced-9

An outer mitochondrial membrane protein in Caenorhabditis elegans that serves as an essential inhibitor of apoptosis by blocking the activity of Ced-4 until an apoptotic signal is received.