120. Which of the following will generally NOT occur if the function of myosin I and myosin II is
blocked?
1. Apoptosis
2. Cell crawling
3. Phagocytosis
4. Vesicle transport

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Correct Answer:

1. Apoptosis

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Explanation:

Myosin I and myosin II are motor proteins that play crucial roles in various cellular processes, particularly in the cytoskeleton dynamics and cell movement. Here’s how blocking these proteins would affect different cellular functions:

1. Apoptosis: Myosin I and myosin II are not directly involved in the initiation or regulation of apoptosis (programmed cell death). Apoptosis primarily involves caspases, cellular signaling pathways, and DNA fragmentation, which are independent of myosin function. Therefore, blocking myosin I and II would generally not directly prevent apoptosis.

2. Cell crawling: Myosin II, in particular, is essential for cell crawling (also called lamellipodia and filopodia formation), a process that allows cells to move along surfaces. Myosin I is involved in the maintenance of the structure of the plasma membrane, further supporting cell motility. Blocking these myosins would impair cell crawling.

3. Phagocytosis: Myosin I plays a critical role in the engulfment of particles during phagocytosis, and myosin II also contributes to the contractile forces needed during the process. Blocking these myosins would inhibit phagocytosis.

4. Vesicle transport: Myosin I and II are involved in vesicle transport, particularly in maintaining the movement of vesicles along actin filaments. Myosin I is especially important for this transport, so blocking it would impair vesicle transport.

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Conclusion:

Blocking myosin I and myosin II would disrupt cell crawling, phagocytosis, and vesicle transport, but apoptosis would generally proceed unaffected. Hence, the correct answer is 1. Apoptosis