What occurs if an enzyme is not present in an organism?

When an enzyme is not present in an organism, the correct outcome is that the organism is incapable of using a metabolic reaction to produce a certain substance. Enzymes are crucial biological catalysts that facilitate biochemical reactions by lowering the activation energy required for those reactions to occur. Without the appropriate enzyme, the metabolic pathway that produces a specific substance would be halted or significantly impaired.

This inability to process the necessary biochemical reactions can lead to a lack of essential products that the organism needs for various physiological functions. For instance, if an enzyme responsible for breaking down a particular substrate into its product is missing, the substrate will accumulate, and the organism will not be able to convert it into the needed product, which can be detrimental to its health and survival.

While other metabolic pathways may exist, the absence of a specific enzyme means that the particular reaction associated with that enzyme cannot proceed, hindering the organism's ability to synthesize certain compounds or complete metabolic cycles effectively. Thus, the absence of the enzyme is critical in understanding metabolic functionality and the overall biochemistry of the organism.