By what process does a section of the plasma membrane of a cell bulge inward to form a pocket around extracellular fluid or molecules that eventually pinches off to become a vesicle contained within the cell

The correct answer is endocytosis.

Endocytosis is an active process in which a cell transports molecules into the cell by engulfing them. Different particles can be engulfed such as large molecules, parts of cells, and even whole cells. Endocytosis can be divided into a few steps:

1. invagination of the plasma membrane,

2. formation of a pocket around the target particle,

3. pinching off the pocket,

4. formation of the intracellular vesicle formed from the plasma membrane.

it has to be understood that the sea water contains a huge amount of sodium and chlorine ions and if they enter the cell of the atlantic cod fish, the cell will shrivel and the fish will die. to avoid such a condition, the fish uses active transport for the purpose of removing the ions against the gradient.

explanation:

the atlantic cod is not a maritime osmoconformer. its native application of salts is less than that of the seawater it lives in. it is continually falling water from the gills to the ocean via osmosis.

countering that, the fish is going to be swallowing seawater. but since its internal collection of salts is lower than seawater, the fish will want to go free of excess salt, and since that's going upon a gradient, then active transport, requiring energy, must be used to pump out the salt. much marine fish use the organs to filter out the salt and these fish discharge very straight urine.