Many water-soluble vitamins are coenzymes. Food items are retained longer. Specialized regions are possible. Digestive enzymes can be more specific. Extensive branching is possible.
Intracellular digestion is easier.
A digestive juice with a pH of 2 probably came from the mouth. Most nutrients are absorbed across the epithelium of the colon stomach. During the process of digestion, fats are broken down when fatty acids are detached from glycerol, and proteins are degraded when amino acids are separated from each other. Both processes can be catalyzed by the same enzyme. Both processes occur intracellularly in most organisms.