When movement occurs against the concentration gradient (low to high), this requires?

When movement occurs against the concentration gradient (low to high), this requires Active Transport.

Explanation:

Substances moving against the concentration gradient, from a lower concentration area to a higher concentration area requires an active transport. It is termed as "active" since there is a requirement of energy usage. This process is in contrast with that of a passive transport. Active transport needs carrier proteins for assistance.

Both active transport and facilitated diffusion requires proteins for assistance in transport process. The difference is that, active transport always takes place against the concentration gradient, thereby moving the substances from lower concentration area to a higher concentration area. The types of proteins that are used for transport will not be same.