Biochemistry is one of the crossover fields of chemistry. Biochemists have to understand both the living world and the chemical world. Even if you don’t want to become a biochemist, you'll still have to understand atoms and molecules as a biologist.
The key thing to remember is that biochemistry is the chemistry of the living world. Plants, animals, and single-celled organisms all use the same basic chemical compounds to live their lives. Biochemistry is not about the cells or the organisms. It's about the smallest parts of those organisms, the molecules. It's also about the cycles that create those biological compounds.