Cell Adhesions & Cell Cycle Control – Vocabulary Review

Vocabulary flashcards covering essential terms from cell adhesion, extracellular matrix, and cell-cycle control topics for Exam IV.

Apical region

The surface of a polarized epithelial cell that faces the lumen or external environment.

Basolateral region

The combined basal and lateral surfaces of an epithelial cell that contact neighboring cells and the underlying ECM.

Basement membrane

Thin, specialized ECM layer that underlies and supports epithelial tissues; composed of basal lamina plus reticular connective tissue.

Basal lamina

Dense, sheet-like portion of the basement membrane immediately beneath epithelial cells; rich in laminin, type IV collagen, and proteoglycans.

Extracellular matrix (ECM)

Network of proteins and polysaccharides secreted by cells that provides structural support, signaling, and anchorage.

Hemidesmosome

Cell-ECM junction that anchors intermediate filaments of epithelial cells to the basal lamina via integrins.

Desmosome

Button-like cell-cell junction that links intermediate filaments of adjacent cells, conferring mechanical strength.

Adherens junction

Cell-cell adhesive junction in which cadherins connect actin microfilaments of neighboring cells.

Tight junction

Seal formed by claudins/occludins at the apical border of epithelial cells that blocks paracellular diffusion.

Gap junction

Intercellular channel made of connexons that allows direct cytoplasmic exchange of small molecules and ions.

Homophilic interaction

Adhesion in which identical molecules on opposing cells bind to each other (e.g., cadherin–cadherin).

Heterophilic interaction

Adhesion in which different molecules on opposing cells bind (e.g., selectin binding to a glycoprotein ligand).

Cadherin

Calcium-dependent adhesion protein mediating homophilic cell-cell binding in adherens junctions and desmosomes.

Lectin

Carbohydrate-binding protein that recognizes specific sugar moieties on glycoproteins or glycolipids.

Cell adhesion molecule (CAM)

General term for membrane proteins that mediate cell–cell or cell–ECM binding (e.g., cadherins, integrins, selectins).

Collagen

Fibrous structural protein forming triple helices; provides tensile strength to connective tissues.

Elastin

ECM protein that forms elastic fibers allowing tissues such as lungs and skin to stretch and recoil.

Proteoglycan

Core protein covalently attached to many glycosaminoglycan chains; confers hydration and resistance to compression.

Fibronectin

Adhesive glycoprotein with RGD motifs that links cells to collagen and organizes the ECM.

Laminin

Cross-shaped adhesive glycoprotein in basal lamina that binds integrins, nidogen, and type IV collagen.

RGD sequence

Arg-Gly-Asp tripeptide in fibronectin and other proteins recognized by many integrins for cell attachment.

Glycosaminoglycans (GAGs)

Long, unbranched, highly sulfated polysaccharides that form hydrated gels within proteoglycans.

Hyaluronate (hyaluronic acid)

Large, nonsulfated GAG that fills space, lubricates joints, and resists compressive forces.

Structural ECM proteins

Collagens and elastins that provide strength and elasticity to tissues.

Protein-polysaccharide complexes

Proteoglycans made of core proteins plus GAGs; create hydrated ECM gels.

Adhesive glycoproteins

Fibronectin, laminin, and others that connect cells to ECM components.

Centriole pair

Two perpendicular microtubule triplet cylinders located in a centrosome; duplicate during S phase.

Centrosome

Major microtubule-organizing center containing a pair of centrioles and pericentriolar material.

Nucleolus

Nuclear subcompartment where rRNA transcription and ribosome assembly occur.

Cleavage furrow

Contractile ring indentation that pinches an animal cell in two during cytokinesis.

Sister chromatids

Identical DNA copies of a chromosome held together by cohesin after replication.

Treadmilling

Dynamic state where microtubules or actin filaments add subunits at one end and lose them at the other.

Dynein

Minus-end-directed motor protein that moves cargo toward the centrosome along microtubules.

Kinetochore

Protein complex assembled on centromeric DNA that attaches chromosomes to spindle microtubules.

Cyclin

Regulatory protein whose concentration rises and falls to activate CDKs at specific cell-cycle stages.

Cyclin-dependent kinase (CDK)

Ser/Thr kinase activated by binding a cyclin; drives progression through cell-cycle checkpoints.

Maturation-promoting factor (MPF)

Mitotic CDK–cyclin complex that triggers entry into M phase when fully activated.

Inhibiting kinase (Wee1)

Kinase that adds an inhibitory phosphate to CDK, keeping it inactive until the proper time.

Activating kinase (Cak)

Kinase that adds an activating phosphate to CDK, priming it for full activation once inhibition is removed.

Ubiquitin ligase

Enzyme that attaches ubiquitin to target proteins, marking them for proteasomal degradation.

Cohesin

Protein complex that holds sister chromatids together from S phase until anaphase.

Separase

Protease that cleaves cohesin, allowing sister chromatids to separate at anaphase.

Securin

Inhibitor that binds separase; degraded by APC/C to initiate chromatid separation.

Anaphase-promoting complex (APC/C)

Ubiquitin ligase that triggers anaphase onset and cyclin degradation to exit mitosis.

Ras pathway

Signal transduction cascade initiated by Ras GTPase that promotes cell proliferation via MAP kinase activation.

Rb protein

Tumor suppressor that binds E2F transcription factors, blocking G1-to-S transition until phosphorylated by CDK-cyclin.

p53

Guardian tumor-suppressor transcription factor activated by DNA damage; induces cell-cycle arrest or apoptosis.

TNF (Tumor Necrosis Factor)

Cytokine that can activate extrinsic apoptosis or inflammation pathways.

Caspase

Cysteine protease that executes apoptosis by cleaving cellular substrates.

Oncogene

Mutated or overexpressed proto-oncogene that drives uncontrolled cell proliferation.

Necrosis

Pathological cell death characterized by swelling, membrane rupture, and inflammation.

Apoptosis

Programmed cell death involving caspase activation, DNA fragmentation, and membrane blebbing without inflammation.

Cytochrome c

Mitochondrial intermembrane protein that, once released into the cytosol, helps activate the apoptosome and caspase-9.

Extrinsic apoptosis pathway

Cell death pathway initiated by external ligand binding to death receptors (e.g., Fas, TNF-R) activating caspase-8.

Intrinsic apoptosis pathway

Mitochondria-mediated pathway triggered by internal stress; involves Bcl-2 family proteins and cytochrome c release.

Kinetochore microtubules

Spindle fibers that attach to kinetochores and pull chromosomes toward poles.

Polar microtubules

Spindle fibers that overlap in the center, sliding apart to elongate the cell during anaphase B.

Astral microtubules

Spindle fibers that radiate toward the cell cortex, helping position the spindle and cleavage furrow.