Answer:
Biosphere
Explanation:
The biosphere is the part of the earth that supports life forms. It includes hydrosphere, atmosphere, and lithosphere. Various ecosystems, aquatic or terrestrial, are present in the biosphere. Biotic and abiotic components of a geographical region that interact with each other together make an ecosystem.
The biotic component of an ecosystem includes all the organisms present in it. Organisms may be unicellular or multicellular. All the organisms are made up of one or more cells. Cells are made up of various biomolecules that interact and enable cells to perform the life processes.
Plasma membrane, cytoplasm and ribosomes.
C) Occurs in areas without soil.
Primary succession occurs in lifeless areas in which <span>soil that is incapable of sustaining life is formed due to lava, sand dunes, and </span><span>rocks left from a retreating glacier.</span>
Answer:
there is no quiz
Explanation:
i have not seen the question
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.
