What principle does Hanawalt's law of biology assert?

Hanawalt's law of biology asserts that chemical reactions can be both spontaneous and non-spontaneous. This principle reflects the understanding that reactions in biological systems can occur without the input of additional energy (spontaneous), or they may require energy to proceed (non-spontaneous). This flexibility in reaction types is essential for understanding metabolic processes in organisms, where the energy requirements and spontaneity of reactions are highly variable and influenced by numerous factors, including environmental conditions and the presence of catalysts.

Recognizing that reactions can be in either category allows for a broader understanding of biochemistry, from cellular respiration to photosynthesis. This principle is foundational in biological chemistry and underpins many processes vital for life.