Answer:
According to the sliding-filament model of contraction, the muscle contraction occur due to the myosin heads propel the actin myofilaments toward the center of the sarcomere. This pulls the Z disks closer together, shortening sarcomere and the entire muscle
Explanation:
In the muscle fiber there are two proteins that facilitate the process of contraction, myosin and actin. Myosin is thicker and more abundant than actin, and its interaction is responsible for the process of muscle contraction.
Both molecules, myosin and actin, form bonds -called cross bridges- where the myosin heads produce the mobilization of actin towards the center of the sarcomere. Z discs are associated with actin myofibrils, so they come close, and promote the shortening of the sarcomere.
This process requires the action of calcium ions, which depolarize the muscle cell and consume energy in the form of ATP.
It should be noted that the myosin and actin molecules do not change their length, but their action causes the muscle fibers to shorten during contraction.
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Types of muscle contraction brainly.com/question/7117064
Answer:
Zygote
Explanation:
A zygote is a (diploid) cell formed through fertilization between two gametes. Zygote cells are eukaryotic, and in the human body, they are the first cell stage of pregnancy.
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Hydrophilic
A phospholipid is comprised of a phosphate hydrophilic head, which means that it is "water-loving," and a fatty acid hydrophobic tail, which is "water-hating." The head and the tail are joined together by a glycerol molecule.
The phosphate head is attracted to water because it is charged (i.e. negatively). Water is a polar molecule, which means that there is an uneven distribution of charges within its molecular structure with the oxygen side being "more negative" than the rest of the atom (which is "more positive" near the hydrogen). Thus, the negatively-charged nature of the phosphate head and the parts of the water molecule which are positively charged enable the two to form an "attraction" towards one another.
On the other hand, the hydrophobic tail is nonpolar, which means that it does not have a "more positive" or "more negative" side or part in its molecular structure. These differences in structure with water make the hydrophobic tail unattracted to water molecules and more attracted to other uncharged, nonpolar molecules (such as fats and oils).
Answer: Option (C)
Explanation: The rocks at the continental crust are present since a long time, and the oldest rocks so far encountered from the continental crust is approximately 4.4 billion years old.
This has been determined by the Uranium-Lead dating method (Ur₂₃₈-Pb₂₀₆).
Oceanic rocks are estimated to be of very recent age i.e about only 180 million years old.
