Medical College Admission Test (MCAT) Practice Exam

The role of the anode in gel electrophoresis is defined by its function as the positive electrode. In this context, the anode attracts anions (negatively charged particles). In a typical gel electrophoresis setup, the gel is placed between two electrodes: the anode (positive) and the cathode (negative).

When an electric field is applied, negatively charged molecules, such as DNA or RNA fragments, migrate towards the anode. This movement occurs because these charged molecules are influenced by the electric field, and they tend to move towards the electrode with the opposite charge.

In gel electrophoresis, the pH can affect the charge of the molecules. At low pH (acidic conditions), molecules may carry a positive charge, which would lead them to migrate towards the cathode instead. Therefore, the anode's role is not related to a neutral or high pH area but is directly tied to its positive charge, assisting in the separation of negatively charged biomolecules.

Identifying the anode as the positive end highlights its critical function in attracting negatively charged species, and this understanding is crucial for interpreting results in gel electrophoresis.