Question

66) The successful transmission of a nervous impulse to a muscle fiber leads to the release of Calcium (Ca2+) from the Sarcoplasmic Reticulum. The role of Ca2+ in muscle contraction is:

		Bind to myosin, which cleaves ATP such that energy can be input into the myosin “heads”, allowing it to perform a power stroke needed to move actin.
		Ca2+ acts in a process that breaks up actin filaments, removing subunits to make them shorter and thus leading to the contraction of the sarcomere.
		Ca2+ binds tropomyosin and triggers a conformation change, such that tropomyosin moves to uncover sites on the thin filament where myosin “heads” can now bind.
		Instead of Sodium (Na+), the Ca2+ ions are utilized to establish a Resting Potential that can then be converted into an Action Potential.
		Provides a chemical messenger that passes through gap junctions in synapses between cardiac muscle cells.

Within the Plant Kingdom, Gymnosperms have completely lost the Alternation of Generation trait, since the haploid Gametophytes have been reduced to microscopic stages that are enclosed within diploid Sporophyte tissues.

True

False

Which of the following statements about plants is TRUE?

		Only vascular plants grow from apical meristems.
		All plants that make seeds also make flowers.
		A mature seed contains the diploid sporophyte.
		Gametophytes produce spores.

Answer 1

1) Ca2+ binds to the troponin, the troponin-Ca2+ complex binds to the tropomyosin and changes the conformation such that the myosin-binding sites on the actin is exposed so that myosin can bind to the actin.

( tropomyosin is found in association with the actin)

so the answer is C) Ca2+ binds tropomyosin and triggers a conformation change, such that tropomyosin moves to uncover sites on the thin filament where myosin “heads” can now bind.

2) gymnosperms have both haploid and diploid stages, the haploid stage is represented by the gametophyte and the gametes which depend on the sporophyte, so gymnosperms have alternation of generation so the given statement is False.

3) gymnosperms have seeds but they do not have flowers, gametophyte produces gametes, the seeds contain the diploid sporophyte which is protected in the seed, so the answer is A mature seed contains the diploid sporophyte.