Salivary amylase breaks down the carbohydrates very large molecules into polysaccharides, smaller ones. These polysaccharides ultimately end up in the lumen of the small intestine, where our pancreatic amylase breaks down the polysaccharide into disaccharides, our maltose, sucrose and lactose. Now, Maltose is broken down at the Brush border into two glucose molecules. Sucrose is broken down at the Brush border by sucrase into fructose and glucose, while lactose is broken down by lactase into galactose and glucose. Also at the brush border. Now, the reason we have to break down the carbohydrates ultimately into their individual monumeric constituents is because the intricacies, the cells of the small intestine, can only absorb these monomers.