Skip to content
Login Register

#cell movement

10 public questions tagged with this topic.

Regeneration -ll

Sea urchin sperm propulsion relies on:

Sea urchin sperm propulsion depends on axonemal dynein motors rather than actin-myosin contractility. Flagellum contains canonical 9+2 microtubule axoneme with outer and inner dynein arms attached to A-tubules of doublets. ATP hydrolysis by dynein heavy chains generates sliding force between adjacent doublets, converted into bending by nexin-dynein regulatory complex and radial spokes. This oscillatory bending propagates from base to tip driving forward motility. Calcium and pH modulate dynein activity switching waveform during chemotaxis. Actin drives acrosomal process extension, myosin contracts fertilization cone, tubulin alone provides tracks without motor capability, requiring dynein for movement.

Ref: NCBI Bookshelf, Cell Biology of Flagella: Dynein-dependent sperm motility and axonemal sliding in sea urchin.

View Details
amphibian Development-l

Gastrulation involves which primary cell movement?

Amphibian gastrulation integrates three movements: epiboly expands animal cap ectoderm over entire embryo via radial intercalation; involution rolls marginal zone mesoderm inside over blastopore lip; invagination and involution driven by bottle cells create archenteron cavity. Convergent extension of dorsal mesoderm narrows and elongates body axis through mediolateral intercalation regulated by non-canonical Wnt planar cell polarity pathway. These coordinated morphogenetic events occur without large growth, reshaping blastula into gastrula with internalized mesoderm and endoderm and dorsal organizer positioned for subsequent neural induction and patterning of body plan.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 8: Gastrulation movements epiboly involution invagination convergent extension.

View Details
amphibian Development-l

The vegetal rotation during gastrulation moves which cells forward?

During late gastrulation, vegetal endoderm undergoes vegetal rotation, an autonomous movement where large yolky cells spread and rotate inside blastocoel. This pushes pharyngeal endoderm, which expresses Xhex and Cerberus, forward along blastocoel roof toward animal pole. Pharyngeal endoderm contacts head mesoderm, facilitating head induction through secreted antagonists Dickkopf, Cerberus, and Frzb. Unlike involution driven by IMZ, vegetal rotation is endoderm-driven, displacing blastocoel and positioning foregut precursors anteriorly for proper gut patterning and archenteron elongation, essential for complete digestive tract formation.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 8: Vegetal rotation moves pharyngeal endoderm during gastrulation.

View Details
Fertilization in mammals-iv

Epiboly during gastrulation involves:

Epiboly is a major morphogenetic movement during gastrulation where sheet-like ectodermal cells spread, flatten and thin to enclose deeper mesodermal and endodermal layers and eventually yolk. It does not involve invagination but rather radial intercalation and expansion of superficial epithelium driven by remodeling of E-cadherin contacts, actin cytoskeleton and differential adhesion. In zebrafish, amphibians and mammalian embryos epiboly helps position ectoderm externally to form epidermis and neural ectoderm. Failure of epiboly leaves involuting marginal cells uncovered, disrupting body axis formation and gastrulation closure.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 8: Gastrulation movements - epiboly, involution and convergent extension mechanisms.

View Details
Basics of Cell Biology

Which of the following is not a function of the cytoskeleton?

Cytoskeletal networks coordinate shape, division, and intracellular logistics. Actin filaments, 7 nm flexible helical polymers of ATP-G-actin nucleated by Arp2/3 at 70 degree branch and formins for linear cables, interact with 50 myosin classes for cortical contraction, formation of contractile ring with myosin II during cytokinesis, lamellipodial protrusion, and vesicle movement near periphery. Microtubules, 25 nm rigid hollow tubes of alpha-beta tubulin heterodimers assembling head to tail with GTP cap regulating dynamic instability, serve as polarized tracks for kinesin families moving outward to plus ends and dynein moving inward, positioning Golgi, endosomes, mitochondria, and assembling mitotic spindle with kinetochore capture ensuring chromosome segregation. Intermediate filaments, 10 nm non-polar rope-like polymers keratin, vimentin, desmin, lamins anchored via plectin and nesprin, provide mechanical resilience against shear stress. Together they govern intracellular transport, mechanical support, and motility. Protein synthesis uses ribosomal peptidyl transferase in cytoplasm and rough ER, not filaments, so translation is not cytoskeletal function.

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 16: Cytoskeleton Functions Overview.

View Details
Cytoskeleton

Which type of myosin is primarily involved in non-muscle cell contractility?

Non muscle contractility underpins stress fiber maintenance, adhesion maturation, morphogenesis and wound closure, distinct from skeletal muscle sarcomeres employing troponin regulation. Myosin II family in non muscle cells includes isoforms IIA, IIB and IIC sharing hexameric composition two heavy chains plus essential and regulatory light chains, forming short bipolar filaments that transiently associate with actin rather than stable thick filaments. Activation occurs via phosphorylation of 20 kilodalton regulatory light chain RLC at Ser19 by calcium calmodulin dependent MLCK and Rho associated kinase ROCK, converting autoinhibited 10S folded conformation to extended 6S assembly competent state enhancing actin activated ATPase. Coordinated pulling of antiparallel actin bundles generates isometric tension, retrograde flow and cortex stiffness. Isoform IIA drives rapid adhesion turnover at leading edge, IIB sustains prolonged tension at rear. Myosin I single headed tension sensor, myosin III adaptation in photoreceptors, myosin VI minus end directed for endocytosis, not primary contractile generator. Therefore myosin II remains central for non muscle contractility.

Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 18: Nonmuscle Myosin II in Contractility.

View Details
General Biology of Protists

Cilia and flagella differ mainly in

Cilia and flagella share fundamentally identical internal architecture termed axoneme composed of nine peripheral microtubule doublets surrounding two central singlets, 9+2 arrangement, radial spokes, and dynein motor arms producing bending via ATP hydrolysis and basal body anchoring. Ultrastructurally and proteomically they are synonymous organelles using tubulin and intraflagellar transport. Distinction rests on length, quantity, and waveform: flagella typically longer, fewer, propelling with undulating waves, while cilia are shorter, numerous, beating coordinately in metachronal waves to move fluids or cells, not internal microtubule composition.

Ref: Campbell Biology 11th ed., Chapter 6 Cilia flagella length number waveform same ultrastructure; Cooper Cell Biology 9+2 axoneme

View Details
General Biology of Protists

Amoeboid locomotion occurs through

Amoeboid locomotion relies on dynamic remodeling of actin cytoskeleton producing cytoplasmic extensions termed pseudopodia meaning false feet. Through polymerization of G-actin at leading edge forming lamellipodia and depolymerization at rear, cytoplasm streams inside projection, adhesion complexes anchor to substratum via transmembrane proteins, propelling cell forward. Small GTPases Rac and Cdc42 regulate branching. Forms include lobopodia in Amoeba, filopodia in foraminifera, and reticulopodia in radiolarians. This crawling mechanism also mediates phagocytic capture of bacteria, distinguishing amoeboid motility from swimming via cilia or flagella requiring microtubules.

Ref: Alberts Molecular Biology Cell amoeboid locomotion pseudopodia actin; Campbell Biology 11th ed., Chapter 28 Protist motility pseudopods organization

View Details
Cell Communication and ECM

ECM degradation during cell migration is mediated by

Matrix metalloproteinases, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

View Details