BIOL 2050 Chapters 9 & 10: Cell Communication and the Cell Cycle

Comprehensive vocabulary flashcards covering cell communication, cell signaling pathways, signal transduction, chromosome structure, cell-cycle regulation, mitosis, and cancer mechanisms from BIOL 2050 Chapters 9 & 10.

Intercellular signaling

Communication between cells.

Intracellular signaling

Communication within a cell.

Ligand

A molecule that binds to a specific receptor and may initiate a signal.

Receptor

A protein that recognizes and binds a particular ligand.

Target cell

A cell that possesses the appropriate receptor and can respond to a signal.

Paracrine signaling

A signaling mechanism where signals diffuse through the extracellular environment to act on nearby cells, producing responses that are often rapid and relatively short-lived.

Endocrine signaling

A signaling mechanism where hormones travel through the bloodstream to act on distant target cells, typically producing slower but longer-lasting responses.

Autocrine signaling

A signaling mechanism where a cell releases a signal that binds to its own receptors or influences similar nearby cells.

Direct signaling

Communication where adjacent cells exchange small signaling molecules or ions through connecting channels, such as gap junctions in animal cells or plasmodesmata in plant cells.

Synapse

The junction where a nerve cell communicates with another cell by releasing neurotransmitters across a synaptic gap.

Internal receptors

Receptors located inside the cell (commonly in the cytoplasm) that bind small, hydrophobic ligands, forming complexes that can bind DNA and directly regulate gene expression.

Cell-surface receptors

Plasma membrane-embedded proteins with extracellular, transmembrane, and intracellular domains that convert external signals into intracellular activity.

Ion channel-linked receptors

Cell-surface receptors that open or close an ion channel upon ligand binding, allowing specific ions to move across the membrane.

G-protein-linked receptors

Cell-surface receptors that activate an associated G-protein upon ligand binding by exchanging GDP for GTP.

Receptor tyrosine kinases (RTKs)

Enzyme-linked cell-surface receptors that often dimerize upon ligand binding and phosphorylate tyrosine residues to initiate downstream signaling.

Nitric oxide (NO)

A gaseous signaling molecule that diffuses through membranes, has a short half-life, and promotes smooth-muscle relaxation and blood-vessel dilation.

Signal transduction

The process through which receptor activation initiates intracellular signaling cascades.

Kinase

An enzyme that catalyzes the transfer of a phosphate group to a target molecule, typically from ATP.

Phosphatase

An enzyme that removes phosphate groups from molecules through dephosphorylation.

Cyclic AMP (cAMP)

A second messenger produced from ATP by adenylyl cyclase that activates protein kinase A (PKA).

Phosphodiesterase

An enzyme that breaks down cyclic AMP (cAMP) into AMP, helping terminate intracellular signaling.

Diacylglycerol (DAG)

A lipid-derived second messenger cleaved from $\text{PIP}_2$ by phospholipase C that remains in the plasma membrane and activates protein kinase C (PKC).

Inositol triphosphate ($\text{IP}_3$)

A second messenger cleaved from $\text{PIP}_2$ by phospholipase C that promotes the release of calcium ions from the endoplasmic reticulum.

Signal amplification

A process in signaling pathways where one activated component activates multiple downstream molecules, increasing the effect of the original signal.

Signal integration

The convergence of signals from multiple different receptors to influence a common intracellular pathway or response.

Genome

The complete genetic information of a cell or organism.

Gene

A DNA sequence that encodes a functional molecule, such as a protein or RNA.

Trait

A characteristic influenced by genetic information and, in many cases, environmental factors.

Chromosome

A cellular structure containing DNA and associated packaging proteins.

Nucleosome

A structural unit of eukaryotic chromatin consisting of a DNA double helix wrapped around histone proteins.

Chromatin

A fiber composed of nucleosomes and associated DNA that forms eukaryotic chromosomes.

Homologous chromosomes

Chromosome pairs that contain the same genes at corresponding locations, with one member inherited from each parent.

Sister chromatids

Identical copies of a replicated chromosome that remain joined together following the S phase.

Centromere

The constricted chromosomal region where sister chromatids remain connected most closely.

Kinetochore

A protein structure located at the centromeric region that attaches chromosomes to spindle microtubules.

Diploid ($2n$)

A cell containing two sets of chromosomes, such as human somatic cells with 46 chromosomes (23 pairs).

Haploid ($n$)

A cell containing one set of chromosomes, such as human gametes with 23 chromosomes.

Interphase

The period of the eukaryotic cell cycle consisting of $G_1$, S, and $G_2$ phases, during which the cell grows, performs normal functions, and duplicates its DNA.

$G_0$ phase

A non-dividing state outside the active cell cycle where cells perform normal functions but are not actively preparing to divide.

Mitosis (karyokinesis)

The division of the cell nucleus that distributes duplicated chromosomes equally into two daughter nuclei.

Cytokinesis

The division of the cytoplasm that completes the formation of two distinct daughter cells.

Prophase

The first stage of mitosis, during which chromosomes condense, the mitotic spindle begins to form, centrosomes move toward opposite poles, and the nucleolus disappears.

Prometaphase

The stage of mitosis where the nuclear envelope breaks down further, kinetochores form at centromeric regions, and spindle microtubules attach to kinetochores.

Metaphase

The stage of mitosis where chromosomes align along the cell's equatorial plane (metaphase plate) with sister chromatids attached to spindle poles.

Anaphase

The stage of mitosis in which sister chromatids separate into individual daughter chromosomes and are pulled toward opposite spindle poles.

Telophase

The final stage of mitosis where separated chromosomes arrive at opposite poles, decondense, the spindle breaks down, and new nuclear envelopes re-form.

Cleavage furrow

An actin-based contractile ring that pinches and constricts animal cells inward during cytokinesis.

Cell plate

A structure formed by fusing Golgi-derived vesicles that develops into a new cell wall between dividing plant daughter cells.

Proto-oncogene

A normal gene involved in regulating cell growth and division that can become an oncogene when mutated.

Oncogene

A mutated or abnormally activated gene that promotes uncontrolled cell proliferation.

Tumor suppressor gene

A gene encoding proteins that restrain cell division, monitor cellular integrity, or trigger repair to prevent tumor development.

Apoptosis

A process of programmed cell death that eliminates damaged or potentially dangerous cells.

$G_1$ checkpoint

A control point near the end of $G_1$ that evaluates cell size, nutrient availability, growth signals, and DNA integrity before committing to DNA replication.

$G_2/M$ checkpoint

A control point that verifies complete DNA replication and checks for DNA damage before allowing the cell to enter mitosis.

Metaphase checkpoint

A checkpoint that monitors whether all chromosomes are properly attached to spindle microtubules before sister chromatids separate.

Cyclins

Regulatory proteins whose concentrations fluctuate throughout the cell cycle to bind and activate cyclin-dependent kinases.

Cyclin-dependent kinases (Cdks)

Enzymes that associate with cyclins to phosphorylate target proteins, driving progression through the cell cycle.

p53

A tumor suppressor protein that detects DNA damage, halts the cell cycle, and stimulates expression of p21.

p21

A negative cell-cycle regulator induced by p53 that binds and inhibits cyclin-Cdk activity, preventing cell-cycle progression.

Retinoblastoma protein (Rb)

A negative cell-cycle regulator that binds and inhibits transcription factor E2F, blocking the expression of genes required for S phase until phosphorylated.