bio cell communication and cycle

Population

A group of individuals of the same species living in the same area; in signaling, this often refers to the density of cells (like bacteria) required to trigger a response.

Signaling molecule

A chemical (ligand) released by a sending cell to convey a message to a target cell.

Target cell

A specific cell that possesses the matching receptor required to bind to and "hear" a signaling molecule.

ligand

A molecule that binds specifically to another molecule (usually a larger one, like a receptor) to initiate a biological process.

quorum sensing

A process where bacteria monitor their population density via signaling molecules to coordinate collective behaviors

hormone

A long-distance signaling molecule produced by glands or specialized cells that travels through the circulatory system to reach distant target cells.

plasmodesmata

Channels through plant cell walls that allow direct cytoplasmic communication and transport between adjacent cells.

sensor

A receptor or cell that detects a change in a physical or chemical variable in the environment.

set point

The ideal or target value at which a physiological system operates (e.g., 37C for human body temperature).

negative feedback

A control mechanism that counteracts a stimulus, bringing a system back toward its set point to maintain stability.

positive feeback

A control mechanism that amplifies a stimulus, moving a system further away from its starting point to complete a specific process.

signal transduction

The process by which an extracellular signal is converted into a specific cellular response through a series of molecular steps.

amplification

The strengthening of a signal during transduction, where one signaling molecule triggers a cascade that activates a massive number of downstream molecules.

G protein-coupled receptor protein (GPCR

A cell-surface receptor that works with the help of a G protein, which acts as an on/off switch for intracellular signaling.

Second messenger:

Small, non-protein, water-soluble molecules or ions (like cAMP) that spread a signal throughout the cytoplasm.

Cyclic adenosine monophosphate (cAMP):

A common second messenger derived from ATP that activates specific proteins, such as protein kinase A

kinase

An enzyme that catalyzes the transfer of phosphate groups from ATP to a specific molecule (phosphorylation), usually activating it.

signaling cascade

A multi-step pathway where one enzyme activates another, which activates another, allowing for regulation and amplification of the signal.

receptor protein kinase

A membrane receptor that, when bound to a ligand, attaches phosphate groups to its own tyrosines or other proteins to trigger a response.

ligand gated channel

A type of membrane receptor containing a "gate" that opens or closes in response to a specific signaling molecule, allowing or blocking the flow of ions.

gene expression

The process by which information from a gene is used to synthesize a functional gene product (usually a protein), often the final "response" of a signaling pathway.

mutation

A permanent change in the DNA sequence that can result in an altered protein/receptor, potentially causing the signaling pathway to be permanently "on" or "off."

agonist

A chemical that binds to a receptor and activates it, mimicking the action of the natural ligand.

antagonist

A chemical that binds to a receptor but does not activate it; instead, it blocks the natural ligand from binding.

blood sugar regulation

The body uses insulin to lower high blood sugar and glucagon to raise low blood sugar, constantly pushing levels back toward a stable set point.

labor

The pressure of the baby on the cervix triggers oxytocin release, which causes stronger contractions, leading to more pressure until the "endpoint" of delivery is reached.