Answer:
The correct answer is 3: "<em>High levels of Ca2+ are expected to be found </em><em>within the sarcoplasmic reticulum</em>".
Explanation:
Muscular contraction is a highly regulated process that depends on free calcium concentration in the cytoplasm. Amounts of cytoplasmic calcium are regulated by <u>sarcoplasmic reticulum</u> that functions as a storage of the ion.
When a nerve impulse reaches the membrane of a muscle fiber, through acetylcholine release, the membrane depolarizes producing the entrance of calcium from <u>extracellular space</u>. The impulse is transmitted along the membrane to the sarcoplasmic reticulum, from where calcium is released. At this point, <em>tropomyosin is obstructing binding sites for myosin on the thin filament</em>. The calcium channel in the sarcoplasmic reticulum controls the ion release, that activates and regulates muscle contraction, by increasing its cytoplasmic levels. When <em>calcium binds to the troponin C</em>, <em>the troponin T alters the tropomyosin by moving it and then unblocks the binding sites,</em> making possible the formation of <em>cross-bridges between actin and myosin filaments.</em> When myosin binds to the uncovered actin-binding sites, ATP is transformed into ADP and inorganic phosphate.
Z-bands are then pulled toward each other, thus shortening the sarcomere and the I-band, and producing muscle fiber contraction.
Light energy is absorbed by a chlorophyll molecule and the photon is passed along a pathway to other chlorophyll molecules. The energy culminates in a molecule of chlorophyll found in the reaction center.
For the first question the answer is C. We know this because Dalton considered matter to be composed of very tiny indivisible particles called atoms which means it can't be further subdivided and thus no sub-atomic particles. And for the second question the answer is the Last one: <span>Ernest Rutherford. The rest of them did not give evidence of the existence of a nucleus or gave poor evidence. Hope this helps</span>
The abdominal cavity does not have a bony protection. The abdominal cavity is barely an unfilled space. It comprises a quantity of critical body organs containing the subordinate portion of the esophagus, the stomach, the small intestine, the colon, the rectum, the liver, the gall bladder, pancreas, spleen, kidneys, and bladder.
