3. Explain why energy is required to move the hydrogen ions across the membrane in the direction indicated in Model 1.

Energy is required to move the hydrogen ions across the membranebecause the hydrogen ions are movingagainst the concentration gradient. High potential energy electrons provide the energy necessary to pumphydrogen ions across the inner mitochondrial membrane.

it would be c. xylem.

a tetrad is the foursome during meiosis made by two homologous chromosomes that have each already replicated into a pair of sister chromatids.