Nutritional Requirements for Animals

1. Nutritional Requirements for Animals • for fuel (chemical energy) • organic materials used in biosynthesis • essential nutrients (substances that • animals can’t make for themselves)

2. The 8 essential amino acids must be obtained from food. • Essential fatty acids are unsaturated. • Vitamins are organic molecules—need small amts • There are 13 essential vitamins. B and C are water-soluble. A, D, E, and K are fat-soluble. • Minerals are inorganic molecules—need small amts

3. Food Processing Steps: 1. Ingestion—eating/feeding 2. Digestion—food is broken down mechanically and chemically into small molecules 3. Absorption—small molecules are absorbed 4. Elimination—undigested material is eliminated

4. Food is processed in specialized compartments. Intracellular Digestion—After food is engulfed by a cell, food is hydrolyzed by enzymes inside vacuoles Eg. Sponge Animal Feeding Mechanisms

5. Extracellular Digestion— Occurs in a compartment continuous with the outside of the body Animals without a full digestive tract have a gastrovascular cavity where food is broken down into smaller pieces. Cells can then engulf smaller particles.

6. Complete digestive tract (alimentary canal)—digestive tube connecting the mouth and anus

7. Human Digestive System Alimentary canal = mouth, esophagus, stomach, small intestine, large intestine, rectum, anus Accessory glands = salivary glands, gall bladder, liver, pancreas 5-10 seconds 2-6 hours 5-6 hours 12-24 hours

8. The Human Digestive System

9. Ingestion digestion absorption elimination Peristalsis is the rhythmic waves of contraction of smooth muscles that push food along. Salivary amylase breaks down food in the mouth. The bolus goes down the esophagus by peristalsis. (Swallowing is voluntary, but after that, everything’s involuntary.)

10. The stomach secretes gastric juices (pH 2) that contain pepsin to digest proteins. HCl (also secreted) converts pepsinogen into pepsin. Pepsin can also cleave pepsinogen. All the stuff mushedup in the stomach is called CHYME.

11. The cardiac orifice prevents backflow into the esophagus. The pyloric sphincter regulates the flow of chyme into the small intestine. Small intestine is long! (Small diameter) This is where most of the digestion & absorption happens. The duodenum is the first section of the small intestine—chyme mixes with digestive juices from the pancreas, liver, gallbladder and intestine. The liver produces bile that’s stored in the gallbladder. Bile helps to digest fats.

12. Macromolecule Digestion Digestion Animation

13. Trypsin and chymotrypsin break peptide bonds. The inactive forms are secreted from the pancreas

14. The small intestine has a large surface area for absorption. Villiproject into the lumen. Absorption takes place in the microvilli.

15. Large intestine—colon, cecum, and rectum Colon—reabsorbs water Cecum—ferments ingested material (mostly plants) Appendix—extension of the cecum—thought to play a minor role in immunity Rectum—stores feces Many bacteria live in the human colon. Some produce vitamins that supplement our dietary intake.

16. Intestinal Adaptations—plants are harder to digest than meat since plant cells have cell walls.

17. Mutualistic Adaptations—many animals have large populations of microorganisms in their alimentary canals to digest cellulose and other macromolecules. Both the host and the microorganism benefit from the products of this digestion. Ruminants are herbivores. They have four chambered stomachs to get the most nutrients from their diets.

18. Regulation of Digestion Digestion is controlled by the enteric division of the autonomic nervous system. The presence of food stimulates peristalsis in the stomach and intestines. The endocrine system also controls digestion by regulating energy storage, glucose levels, and appetite.

19. If energy taken in > needed excess is stored in liver and muscle cells as glycogen. Once glycogen stores are full, additional excess energy is stored in fat in adipose tissue. insulin The pancreas detects blood glucose levels. Insulin decreases blood glucose levels. Glucagon increases blood glucose levels. glucagon

20. Hormonal Control of Digestion Gastrin stimulates gastric juice secretion when food is present. Secretin stimulates pancreas to secrete bicarbonate when chyme is in duodenum. CCK (cholecystokinin) stimulates gallbladder to release bile when aa or fatty acids are in duodenum.

21. Appetite is regulated by hormones that affect the satiety center of the brain. Ghrelin triggers feelings of hunger. Insulin suppresses appetite after eating. Leptin suppresses appetite when enough body fat is present. PYY—suppresses appetite after eating (counters ghrelin)

22. Mutations in the gene for leptin or the leptin receptor have been found to cause obesity in mice. The mouse on the right lacks a normal leptin receptor.