A general rule relating the capacity of a specific animal's digestive system to provide adequate access to substrates for biosynthesis of cellular components, as well as fuel molecules needed for ATP production, is that the animal should have access to

a diet that matches the "food pyramid" for the species

Excessive iron absorption and accumulation to toxic levels is associated with

the genetic disorder known as hemochromatosis

Fat digestion yields fatty acids and glycerol, whereas protein digestion yields amino acids; both digestive processes

add a water molecule to break bonds (hydrolysis)

Ingested dietary substances must cross cell membranes to be used by the body, a process known as

absorption

In marine sponges, intracellular digestion of peptides is usually immediately preceded by

endocytosis

An advantage of a complete digestive system over a gastrovascular cavity is that the complete system

allows for specialized regions with specialized functions

Because the foods eaten by animals are often composed largely of macromolecules, this requires the animals to have mechanisms for

enzymatic hydrolysis

The large surface area in the gut directly facilitates

absorption

In the digestive system, peristalsis is

smooth muscle contractions that move food along the esophagus

After ingestion by humans, the first category of macromolecules to be chemically digested by enzymes in the mouth is

carbohydrates

Salivary amylase digests

starches

Digestive secretions with a pH of 2 are characteristic of the

stomach

Pepsin is a digestive enzym that

begins the hydrolysis of proteins in the stomach

Upon activation by stomach acidity, the secretions of the parietal cells

initiate the digestion of protein in the stomach.

The bile salts

emulsify fats in the duodenum

Complex nutrients are digested and then absorbed into the lymph or bloodstream as

monomers

An enzyme with high activity in an acidic environment is

pepsin

The absorption of fats differs from that of carbohydrates in that the

most absorbed fat first enters the lymphatic system, whereas carbohydrates directly enter the blood

For a nondiabetic person, the glucose concentration in this part of the vasculature varies more than in any other part.

hepatic portal vessel

Glandular secretions that are released initially as inactive precursors of digestive enzymes are the

protein-digesting enzymes

Because adult lampreys attach onto the surface of large fish for long periods of time to feed on body fluids, they can accomplish nutritional balance without need for a

stomach

Constipation can result from the consumption of a substance that

promotes water reabsorption in the large intestine

Historically inaccurate diagnosis of acid reflux disorders and gastric ulcers has been improved by

the diagnosis and treatment of H. pylori infection

A hiatal hernia that disrupts the functional relationship between the smooth muscle in the esophagus and that in the stomach would be most likely to increase the frequency of

gastric reflux

The cells that secrete the acidic components of stomach juices are

the parietal cells of the stomach

Stomach cells are moderately well adapted to the acidity and protein-digesting activities in the stomach by having

a thick, mucous secretion and active mitosis of epithelial cells