What is the role of calcium ions during contraction of a skeletal muscle?
What will be an ideal response?
At rest, calcium ions are stored in the sarcoplasmic reticulum. Once the muscle cells have been stimulated or excited, calcium ions are released into the area of the contractile proteins. The ions bind to troponin, which results in a shift in position of the troponin-tropomyosin complex. This is necessary to expose the myosin binding sites on the actin molecule. Once exposed, the myosin heads can bind to the actin and cause the filaments to slide relative to each other, shortening the sarcomere.
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Consider a diploid species where n=5. If an individual of this species was found to have 11 chromosomes, it would be categorized as
A. polyploid. B. aneuploid. C. tetraploid D. monosomic. E. triploid.
What would plants living in areas with moist soils be most likely to have?
A) many narrow, tapering tracheids B) lots of wide, perforated vessel elements C) frequent embolisms and loss of tension D) reduced transpiration rates
What are the three types of tissues comprising the ground tissue system, and what are their functions? What will be an ideal response?
The fertilization of an egg by a sperm produces a cell called a/an:
A) oocyte. B) ovum. C) gamete. D) zygote.