Final answer:
Metabolic disorders affecting the central nervous system often result in the accumulation of proteins. Examples include Cushing syndrome, Addison's disease, Alzheimer's disease, and Parkinson's disease. These disorders involve dysfunction of proteins or enzymes critical to metabolic pathways, leading to the accumulation of abnormal protein aggregates in the central nervous system. Therefore, the correct option is d) proteins.
Step-by-step explanation:
Metabolic disorders affecting the central nervous system often result in the accumulation of proteins. Disorders such as Cushing syndrome, Addison's disease, Alzheimer's disease, and Parkinson's disease involve dysfunction of proteins or enzymes critical to metabolic pathways, leading to the accumulation of abnormal protein aggregates in the central nervous system. For example, in Cushing syndrome, excess production of the hormone cortisol causes rapid weight gain, depression, and anxiety. In Alzheimer's disease, the accumulation of beta-amyloid plaques, composed of malfunctioning proteins, is associated with neurodegeneration. Therefore, the correct option is d) proteins.