What biological process describes the breakdown and absorption of nutrients?

The biological process that describes the breakdown and absorption of nutrients is digestion. This involves several steps that begin in the mouth, where food is mechanically broken down and chemically processed by saliva. As the food travels through the digestive tract, it is further broken down by various enzymes and acids in the stomach and intestines.

Nutrients from the digested food are then absorbed in the small intestine, entering the bloodstream and providing necessary components, such as vitamins, minerals, carbohydrates, proteins, and fats, to the body. This process is crucial for maintaining energy levels, growth, and overall health, as it allows the body to utilize the essential compounds found in food.

Other processes listed do not pertain to the breakdown and absorption of nutrients. Excretion refers to the removal of waste products from the body, respiration involves the exchange of gases, usually related to oxygen and carbon dioxide, and circulation pertains to the movement of blood and nutrients throughout the body but is not directly responsible for the breakdown of food.