How exactly MOV AX will load data from RAM?
I am not sure if this is actually on-topic here, but anyway.

The main memory in x86 architectures is addressed byte-wise. If you want to retrieve 16 bits from address 2000h (note that AX is a 16 register), then you will need to read 8 bits from 2000h and 8 bits from 2001h. This is why the operation needs to read "2 cells". Note that the term "cell" is not the correct one, as it typically refers to individual 1-bit memory units without addressing logic.

Note that the processor actually doesn't read the two bytes separately. Rather, the content from bytes 2000h and 2001h are fetched at the same time as the data bus to cache and main memory is >8 bits and the addresses you have here as examples are aligned, so the underlying architecture supports the parallel read.