HUMAN PHYSIOLOGY
LOCOMOTION AND MOVEMENT
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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polymeric F actin and monomeric G actin
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monomeric F actin, polymeric G actin
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globular F and G actin
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more then one correct
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Detailed explanation-1: -Actin is a globular protein that exists in the monomeric form (G-actin) and polymeric filamentous form (F-actin).
Detailed explanation-2: -Individual actin molecules are globular proteins of 375 amino acids (43 kd). Each actin monomer (globular [G] actin) has tight binding sites that mediate head-to-tail interactions with two other actin monomers, so actin monomers polymerize to form filaments (filamentous [F] actin) (Figure 11.2).
Detailed explanation-3: -Actin is often the most abundant protein in cells. G-actin, the globular monomeric form of actin, has a molecular weight of about 42 kDa.
Detailed explanation-4: -Hence monomeric actin is known as G-actin.
Detailed explanation-5: -ATP-bound G-actin is the normal substrate for filament formation. It may be induced to polymerize to ATP-containing F-actin, which is energetically favored under physiological conditions. However, F-actin is a slow ATPase, such that the filament soon contains just ADP. ADP F-actin is less stable than ADP G-actin.