Answer:
Exoskeletons provide less mechanical leverage.
Explanation:
There are two types of skeleton in living beings: the endoskeleton (which vertebrates possess, is lined with epithelial tissue and has bones and cartilage) and the exoskeleton, a skeletal structure that is located outside the body of the living being. , is an external skeleton. They are common in invertebrate animals, which have no internal bone structure.
The exoskeleton is a tough but flexible outer layer, not formed by bones, unlike the vertebrate endoskeleton. Its function is mechanical, chemical and biological protection, avoid excessive water loss, muscle support and serves as a connecting point for legs, wings and other appendages. However, this type of skeleton provides less mechanical leverage.
On the other hand, the endoskeleton is the name given to the internal skeleton, which is inside the body. This body structure is mainly seen in vertebrate animals and has the function of supporting and moving the body, as well as protecting some internal organs. Unlike exoskeleton, the endoskeleton provides more mechanical leverage.
The answer is A, convergence.
Covalent Bonds: A Hydrogen Example. A covalent bond is a chemical bond that comes from the sharing of one or more electron pairs between two atoms. Hydrogen is an example of an extremely simple covalent compound. A hydrogen example.
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.
