Final answer:
The correct sequence in a crawling cell is a protrusion at the cell's leading edge, attachment, pulling forward, and release and retraction of the trailing edge, involving actin dynamics and myosin contraction. The correct option is A) protrusion at the cell's leading edge, attachment of protrusion, pulling the cell forward, release and retraction of trailing edge
Step-by-step explanation:
The correct order of events in a crawling cell is protrusion at the cell's leading edge, attachment of the protrusion, pulling the cell forward, and release and retraction of the trailing edge. During the crawling of a cell such as a fibroblast:
- First, the cell extends a protrusion, like a lamellipodium or filopodia, at the front.
- Next, this protrusion attaches to the substrate through focal adhesions.
- Subsequently, the cell body pulls itself forward towards the leading edge by contraction of actin-myosin fibers.
- Finally, the cell releases the adhesions at the back and the retraction fibers at the rear of the cell are drawn into the cell body, thus moving the trailing edge forward.
This process involves actin assembly and disassembly, as well as myosin-mediated contraction, which is essential for the movement of the cell on a substrate.
The correct option is A) protrusion at the cell's leading edge, attachment of protrusion, pulling the cell forward, release and retraction of trailing edge