# Is hydrolysis of polypeptides and polysaccharides “anabolic” or “catabolic”

When a polysaccharide or polypeptide is hydrolyzed into mono-saccharides or amino acids, the building blocks can be oxidized to release energy. The oxidation is considered to be catabolic since it reduces the building blocks to simple compounds: carbon dioxide, water, ammonia, and releases energy.

1. Is the process of hydrolysis that breaks up polypeptides and polysaccharides a net endothermic or exothermic process?

2. Do the free amino acids and monosaccharides have more or less stored energy than the polypeptide or polysaccharide that they were broken down from?

3. Is it proper to call the isolated process of "hydrolysis" of proteins and polysaccharides "catabolic"?

4. Are protein synthesis, glycogen synthesis, (and triglyceride formation), by dehydration synthesis processes that require energy or release energy. I think that they release energy which is semantically interesting since protein and glycogen synthesis are the main examples of anabolism in the body but may actually release energy which is a key component of the definition of catabolism. Even if the energy released from protein synthesis is not generating ATP directly, wouldn't the heat produced conserve ATP in the long run.

1) Is the process of hydrolysis that breaks up polypeptides and polysaccharides a net endothermic or exothermic process?

Under physiological conditions, it is a process that goes forward, i.e. the Gibbs energy is negative. As a consequence, it can happen outside of cells in the absence of ATP. When we eat, the hydrolysis of polysaccharides starts in our mouths, while the hydrolysis of proteins occurs under harsher (acidic) conditions in the stomach and continues in the intestine (slightly basic conditions).

For warmblooded animals like us, exothermic or endothermic is less important, but you could look it up.

2) Do the free amino acids and monosaccharides have more or less stored energy than the polypeptide or polysaccharide that they were broken down from?

Less Gibbs energy, as the hydrolysis is spontaneous. However, this Gibbs energy is not captured (different from downstream oxidation of building blocks to $$\ce{CO2}$$, which is coupled eventually to synthesis of ATP).

3) Is it proper to call the isolated process of "hydrolysis" of proteins and polysaccharides "catabolic"?

If your definition is just breaking down complicated molecules into simple ones, then you would call it catabolic. If you also require that Gibbs energy is captured in a coupled reaction, then you would classify these reactions as digestion, and the downstream oxidation to carbon dioxide as catabolism.