Even though the cells in our body rely on glucose as a source of energy, they can replace glucose's energy with lipids or proteins' energy. In the brain's case, this is not possible since the blood-brain barrier, which is a highly selective barrier between the blood and the extracellular fluid in the central nervous system, allows the passage of glucose as the only source of energy. This is why maintaining the correct levels of glucose is crucial for the metabolism in the brain.
Explanation: Some regions of a polypeptide may coil or fold back on themselves. This is called secondary structure, and the coils or folds are held in place by hydrogen bonds.
