Question8 1 pts Which of the following statements about the actin cytoskeleton i

Question

Question8 1 pts Which of the following statements about the actin cytoskeleton is FALSE? O Extracellular signals can regulate the assembly of the actin cytoskeleton Migration of neutrophil cells from the blood stream to a site of wounding involves regulation of the actin cytoskeleton by paracrine signals. Extension of lamellipodia during cell migration requires actin to interact with the keratin extracelalar matrix protein. O Different members of the Rho family of monomeric GTPases, can direct dramatically different arrangements of actin filaments Question 9 1 pts Which of the following staterhents about muscle contraction is TRUE 0 in a myofibril of a resting muscle cell, the ATP required to initiate muscle contraction has already been hydrolyzed to ADP Pi O ATP released from the sarcoplasmic reticulum is hydrolyzed by tropomyocin, resulting in the activation of myosin. Shortening of actin filaments leads to sarcomere shortening, resulting in muscle contraction. Muscle contraction is an example of extracellular signals rearranging cytoskeletal architecture. Binding of calcium to myosin heads leads to their activation, driving a power stroke. ML

Explanation / Answer

8. Option 3rd is the correct answer.  Polymerization and depolymerization of actin filament create protrusive force required to stretch the membrane and allow the lamellipodia to extend.

9. Option 3rd is the correct answer. Shortening of actin filaments causes shortening of sarcomere which results in muscle contraction. According to sliding filament theory the myosin filaments remained central and constant in length and contraction arises due to shortening of actin filaments.

10. Last option is the correct answer. Unlike microtubules and microfilaments Intermediate filaments do not contain polarity and thus, intermediate filaments cannot serve as basis for cell motility and intracellular transport.

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