Final answer:
True. Glucose and amino acids cross the blood-brain barrier slowly through carrier-mediated transport mechanisms. This selective transport is due to the unique regulatory functions of the brain's blood supply.
Step-by-step explanation:
The statement that glucose and amino acids cross the blood-brain barrier (BBB) slowly through carrier-mediated transport mechanisms is True. Due to the unique properties of the BBB, direct diffusion of many substances into the central nervous system (CNS) is restricted. Substances such as glucose, the brain's main energy source, and amino acids rely on specific transport proteins to move across the blood-brain barrier. This selective transport allows these essential nutrients to be used by the brain while keeping out potentially harmful agents.
In the context of physiology, glucose transport proteins, or GLUTs, are responsible for shuttling glucose through cell membranes by facilitated diffusion. Similarly, amino acids are absorbed via specific carrier-mediated systems designed to transport polar nutrients efficiently, including the L-type Amino Acid Transporter. The existence of these transport mechanisms reflects the brain's need to regulate its environment tightly, which is critical for its sensitive functions.