Which of the following is true about anabolic reactions?

Anabolic reactions are characterized by their role in building complex molecules from simpler ones. This process typically requires an input of energy to facilitate the synthesis of larger, more complex structures such as proteins, nucleic acids, and polysaccharides. During anabolic processes, energy is absorbed from metabolic pathways to promote the formation of these biomolecules. This makes the statement about requiring energy input accurate, as it highlights the energy-demanding nature of synthesis in biological systems.

It is important to note that anabolic reactions are distinct from catabolic reactions, which involve the breakdown of complex molecules into simpler ones, leading to the release of energy. This differentiation reinforces why the correct answer emphasizes the need for energy in anabolic processes rather than energy release or breakdown of glucose. Furthermore, while some anabolic reactions may take place in organelles like the mitochondria (for example, certain aspects of synthesis linked to cellular respiration), this is not a universal trait for all anabolic processes, making it an insufficient reason as a defining characteristic.