1. Active transport uses energy to move molecules against a concentration gradient, from an area of lower concentration to an area of higher concentration. This process is used to move molecules that are essential for the cell, such as glucose and amino acids, into the cell.

2. Passive transport does not use energy to move molecules. Instead, molecules move down a concentration gradient, from an area of higher concentration to an area of lower concentration. This process is used to move waste products and other molecules that the cell does not need out of the cell.