ap bio chapter 7

quorum sensing

A system of communication used by bacteria to coordinate behavior based on population density through signaling molecules.

taxis

A directional movement of an organism or cell toward or away from a stimulus.

chemotaxis

Movement of a cell in response to a chemical stimulus.

ligands

A signaling molecule that binds to a receptor protein and triggers a cellular response.

receptors

Proteins on or in a cell that bind specific ligands and initiate signal transduction pathways.

signal transduction

The process by which a cell converts an external signal into a specific internal cellular response through molecular steps.

ligand-gated ion channel

A receptor that opens or closes an ion channel when a ligand binds.

catalytic (or enzyme-linked) receptor

A receptor that activates an enzyme or has enzymatic activity when a ligand binds.

G-protein-linked receptor

A receptor that transmits a signal inside the cell through a G protein when a ligand binds.

homeostasis

The maintenance of stable internal conditions within an organism or cell.

negative feedback pathway (feedback inhibition)

A regulatory mechanism in which the final product inhibits an earlier step to maintain homeostasis.

positive feedback pathway

A regulatory mechanism in which the response amplifies the original stimulus.

cell division

The process by which a parent cell divides into two or more daughter cells.

G₀ phase

A resting or nondividing state in which a cell exits the cell cycle.

cell cycle

The ordered sequence of events in which a cell grows, replicates DNA, and divides.

interphase

The phase of the cell cycle in which the cell grows and prepares for division (G₁, S, G₂).

mitosis

The division of the nucleus into two genetically identical nuclei.

G₁ phase

The first growth phase of interphase when the cell grows and performs normal functions.

S phase

The phase of interphase during which DNA is synthesized.

G₂ phase

The phase of interphase when the cell prepares for mitosis.

sister chromatids

Two identical copies of a chromosome joined at the centromere.

centromere

The region of a chromosome where sister chromatids are attached and spindle fibers connect.

cyclins

Regulatory proteins that control progression through the cell cycle.

cyclin-dependent kinases (CDKs)

Enzymes activated by cyclins that regulate the cell cycle by phosphorylating proteins.

cell cycle checkpoints

Control points where the cell cycle is regulated to ensure proper division.

apoptosis

Programmed and controlled cell death.

cancer

A disease characterized by uncontrolled cell division.

oncogene

A mutated gene that promotes uncontrolled cell division.

tumor suppressor gene

A gene that normally slows or stops cell division or promotes apoptosis.

prophase

The stage of mitosis when chromosomes condense and spindle fibers form.

metaphase

The stage of mitosis when chromosomes line up at the metaphase plate.

anaphase

The stage of mitosis when sister chromatids separate and move to opposite poles.

telophase

The stage of mitosis when nuclear membranes reform around chromosomes.

chromatin

The uncondensed form of DNA and proteins in the nucleus.

spindle fibers

Microtubules that move chromosomes during cell division.

kinetochores

Protein structures on the centromere where spindle fibers attach.

metaphase plate

The imaginary line at the center of the cell where chromosomes align.

cytokinesis

The division of the cytoplasm into two daughter cells.

cleavage furrow

The groove that forms in animal cells during cytokinesis.

cell plate

A structure that forms in plant cells during cytokinesis and becomes the new cell wall.