Final answer:
Glucose and galactose are absorbed into enterocytes via secondary active transport using sodium-coupled transport proteins, which rely on sodium gradient maintained by the Na+/K+ ATPase pump. The energy derived from ATP hydrolysis is used to sustain the gradient, allowing the monosaccharides to move against the concentration gradient into the cells.
Step-by-step explanation:
The monosaccharides glucose (glu) and galactose (gal) are absorbed into the enterocytes (intestinal cells) through a process known as secondary active transport, which is a type of active transport. In this process, glucose and galactose are carried into the epithelial cells by protein carriers that utilize the sodium gradient maintained by the Na+/K+ ATPase pump. The transport proteins bind both the monosaccharides and sodium ions (Na+) from the small intestine lumen. Once inside the cell, glucose and galactose are released into the cytoplasm and can then move into the bloodstream via facilitated diffusion.
Active transport is required for glucose and galactose absorption when their concentration in the lumen is lower than in the blood. The energy for this transport comes from ATP hydrolysis, which is used to pump Na+ ions out of the cell in exchange for K+ ions, maintaining a low Na+ concentration inside the cell. This sodium gradient is crucial for the function of the Na+-coupled glucose transport proteins that facilitate the uptake of monosaccharides against their concentration gradient.