Z-line

(noun)

Neighbouring, parallel lines that define a sarcomere.

Related Terms

Examples of Z-line in the following topics:

  • Sliding Filament Model of Contraction

    • A sarcomere is defined as the segment between two neighbouring, parallel Z-lines.
    • Actin myofilaments attach directly to the Z-lines, whereas myosin myofilaments attach via titin molecules.
    • Surrounding the Z-line is the I-band, the region where actin myofilaments are not superimposed by myosin myofilaments.
    • The I-band is spanned by the titin molecule connecting the Z-line with a myosin filament.
    • Titin molecules connect the Z-line with the M-line and provide a scaffold for myosin myofilaments.

  • Binary Fission

    • The formation of a ring composed of repeating units of a protein, FtsZ, directs the partition between the nucleoids.
    • Formation of the FtsZ ring triggers the accumulation of other proteins that work together to recruit new membrane and cell wall materials to the site.
    • In addition, both FtsZ and tubulin employ the same energy source, GTP (guanosine triphosphate), to rapidly assemble and disassemble complex structures.
    • FtsZ and tubulin are homologous structures derived from common evolutionary origins.
    • In this example, FtsZ is the ancestor protein to tubulin (a modern protein).

  • Sex Determination

    • Avian sex determination is dependent on the presence of Z and W chromosomes.
    • Homozygous for Z (ZZ) results in a male, while heterozygous (ZW) results in a female.
    • In birds, Z and W chromosomes determine sex, with females being the heterozygous sex.

  • The lac Operon: An Inducer Operon

    • The lac operon encodes the genes necessary to acquire and process the lactose from the local environment, which includes the structural genes lacZ, lacY, and lacA. lacZ encodes β-galactosidase (LacZ), an intracellular enzyme that cleaves the disaccharide lactose into glucose and galactose. lacY encodes β-galactoside permease (LacY), a membrane-bound transport protein that pumps lactose into the cell. lacA encodes β-galactoside transacetylase (LacA), an enzyme that transfers an acetyl group from acetyl-CoA to β-galactosides.
    • Only lacZ and lacY appear to be necessary for lactose catabolism.

  • Malpighian Tubules of Insects

    • Malpighian tubules line the gut of some species of arthropods, such as bees.
    • They are lined with microvilli for reabsorption and maintenance of osmotic balance.
    • Instead, urine is produced by tubular secretion mechanisms by the cells lining the malpighian tubules that are bathed in hemolymph.
    • There are exchange pumps lining the tubules which actively transport H+ ions into the cell and K+ or Na+ ions out; water passively follows to form urine.

  • Epithelial Tissues

    • They also line the lumens of organs in a single layer or multiple layers of cells.
    • Columnar epithelial cells lining the respiratory tract appear to be stratified.
    • Goblet cells are interspersed in some tissues (such as the lining of the trachea).
    • The nuclei line up at the base of the cells.
    • Pseudostratified columnar epithelia line the respiratory tract.

  • Mendel's Law of Independent Assortment

    • For more complex crosses, the forked-line and probability methods are preferred.
    • To prepare a forked-line diagram for a cross between F1 heterozygotes resulting from a cross between AABBCC and aabbcc parents, we first create rows equal to the number of genes being considered and then segregate the alleles in each row on forked lines according to the probabilities for individual monohybrid crosses.
    • While the forked-line method is a diagrammatic approach to keeping track of probabilities in a cross, the probability method gives the proportions of offspring expected to exhibit each phenotype (or genotype) without the added visual assistance.
    • The forked-line method can be used to analyze a trihybrid cross.
    • Use the probability or forked line method to calculate the chance of any particular genotype arising from a genetic cross

  • Organogenesis

    • It forms the epithelial lining of the whole of the digestive tube (except part of the mouth and pharynx) and the terminal part of the rectum (which is lined by involutions of the ectoderm).
    • It also forms the lining cells of all the glands which open into the digestive tube, including those of the liver and pancreas; the epithelium of the auditory tube and tympanic cavity; the trachea, bronchi, and air cells of the lungs; the urinary bladder and part of the urethra; and the follicle lining of the thyroid gland and thymus.

  • Growth of Bone

    • All that remains of the epiphyseal plate is the epiphyseal line .
    • Osteoclasts, cells that work to break down bone, resorb old bone that lines the medullary cavity.
    • As a bone matures, the epiphyseal plate progresses to an epiphyseal line.
    • (b) Epiphyseal lines are the remnants of epiphyseal plates in a mature bone.

  • Animal Characterization Based on Features of Embryological Development

    • The endoderm gives rise to the stomach, intestines, liver, pancreas, and the lining of the digestive tract, as well as to the lining of the trachea, bronchi, and lungs of the respiratory tract.
    • Eucoelomates (or coelomates) have a true coelom that arises entirely within the mesoderm germ layer and is lined by an epithelial membrane.
    • The epithelial membrane also lines the organs within the coelom, connecting and holding them in position while allowing them some free motion.
    • Eucoelomates have a body cavity within the mesoderm, called a coelom, which is lined with mesoderm.