All life forms currently have a basic cell membrane so we hypothesize that the earliest cells also had membranes. It is likely that the primordial environment was acidic. In order for a cell to function in this type of environment, the cell membrane would have to include

A. a totally nonpermeable membrane.
B. a sodium (Na+) pump.
C. mitochondria underneath in order to provide energy for active transport.
D. a proton (H+) pump.
E. an acid-proof cell wall.


Answer: D

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What will be an ideal response?

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