Ch.21 Nutrition and Digestion

WHAT IS ACID PEPSINOGEN AND HCl?

Stomach stores food and breaks it down with acid and enzymes. In this case, Acid is pH 2, and parietal cells secrete hydrogen and chloride ions, which combine to make HCl. Acid kills bacteria in food and breaks apart cells in food. Pepsinogen and HCl produce pepsin. Pepsin production activates more pepsinogen production, which is a positive feedback for digestion. Pepsin begins the chemical digestion of proteins. Acidic gastric juices mix with food to produce acid chyme.

WHAT ARE THE FUNCTIONS OF THE LIVER?

The liver performs many functions. One of the main function of liver is processing nutrient laden blood from the intestines. Blood from the digestive tract drains to the liver. Also other functions are glucose in blood is converted to glycogen and stored in the liver. Liver synthesizes many proteins including blood clotting proteins and lipoproteins that transport fats and cholesterol. Liver also changes toxins to less toxic forms and it produces bile.

WHAT IS THE HUMAN HEALTH PROBLEM OF OBESITY?

Obesity may reflect our evolutionary past. Overnourishment is consuming more food energy than is needed. World health organization recognizes obesity as a major global health problem. Of all the people in the United States, 30% are obese, 35% are overweight, and 155 of children and adolescents are overweight. Obesity leads to diabetes, cancer, and cardiovascular disease.

SUMMARY:

Most animals are herbivores, carnivores, or omnivores. Animals obtain and ingest their food in different ways, suspension feeding, substance feeding, fluid feeding, or bulk feeding. And food is processed ingestion first, digestion second, absorption third, and elimination last. Sponges digest food in vacuoles, while most animals digest food in compartments. Cnidarians and flatworms have a gastrovascular cavity with a single opening, the mouth. Teeth break up food, saliva moistens it, and tongue tastes, shapes the bolus of food, and moves it toward the pharynx. The Heimlich maneuver can dislodge food from the pharynx or trachea during choking. Brain damage will occur within minutes if no airway is open. Nutrients pass across the epithelium and into blood. Blood flows to the liver where nutrients are processed and stored. Blood from the digestive tract drains to the liver. The length of the digestive tract often correlates with diet. For example herbivores and omnivores have relatively longer digestive tracts than carnivores. Many hervivores have specializations of the intestine that promote the growth of cellulose.

Nutrients are oxidized inside cells to make ATP. ATP is the main energy currency in a cell. Excess energy can be stored as glycogen or fat. The eight essential amino acids can obrained from animal protein, and the proper combination of plant foods. The essential proteins are the ones that animals cannot produce. Food labels indicate serving size, calories per serving, amounts of selected nutrients per serving and as a percentage of daily value, and recommendations for daily limits of selected nutrients.

KEY TERMS:

- Herbivores: plant eaters

- Carnivores: meat eaters

- Omnivores: eating both plants and other animals

- Pyloric sphincter: regulates the passage of food from the stomach to the small intestine

- Diarrhea: occurs when too little water is reclaimed

- Constipation: occurs when too much water is reclaimed

- Colon bacteria: production of biotin, vitamin K, B vitamins

- Appendix: located near the small intestine and colon and makes a minor contribution to immunity

- BMR: the energy a resting animal requires each day

- Metabolic rate: the BMR plus the energy needed for physical activity

Valine is needed for muscle metabolism, tissue repair, and for the maintenance of proper nitrogen balance in the body. Valine is found in high concentration in the muscle tissue. It can be used as an energy source by muscle tissue. It may be helpful in treating livere and gallbladder disorders, and it is good for correcting the type of severe amino acid deficiencies that can be caused by drug addiction. Dietary sources of valine include dairy products, grain, meat, mushrooms, peanuts, and soy proteins.

5 FACTS:

1) Mechanical digestion breaks food down into smaller pieces.

2) Chemical digestion breaks down large organic molecules into their components.

3) Most animals have an alimentary canal with mouth, anus, and specialized regions.

4) Enzymes from cells of the intestine continue digestion.

5) Small intestine is the major organ of chemical digestion and nutrient absorption.