How scientists use repeated trials and replication in conducting experiments

Most animal cells membranes have proteins that pump ions out of the cell and potassium ions into the cell

What molecules will be best used to compare different species with the exact same sequence of amino acids? why would two species have the same protein even if the molecules in question is different? (hint: transcription to translation to protein).

The united states uses which source of energy to produce almost 40 percent of its electricity