Final answer:
Some biological reactions can occur without enzymes. While enzymes are vital for most metabolic processes, they are not mandatory for all biological reactions. They serve mainly to reduce activation energy allowing reactions to occur at body temperature.
Step-by-step explanation:
The correct statement about biological reactions is: Some biological reactions can occur without enzymes. Biological reactions, including both anabolic and catabolic processes, are a fundamental aspect of life processes. While many of these reactions do require enzymes to catalyze and speed up the reactions within the metabolic pathways, not all biological reactions strictly require enzymes.
It is crucial to know that the standard free energies of reactions are not always negative; this value can be either positive or negative, depending on whether the reaction is endergonic (energy-absorbing) or exergonic (energy-releasing). Moreover, not all biological reactions need to be linked to other reactions to occur, although many important reactions in the cell are coupled to the hydrolysis of ATP, which is an exergonic process.