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  1. 1. Nutrition and Digestion Lecture 5-2
  2. 2. Biology and Society: Eating Disorders <ul><ul><li>Millions of Americans suffer from eating disorders </li></ul></ul><ul><ul><ul><li>Including anorexia and bulimia. </li></ul></ul></ul>Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings <ul><ul><li>-The causes of these diseases are unknown. </li></ul></ul><ul><ul><li>-Popular culture and the media may promote unhealthy body images. </li></ul></ul>
  3. 3. Overview of Animal Nutrition <ul><ul><li>Animals are heterotrophs, organisms that must feed on other organisms. </li></ul></ul><ul><ul><li>Herbivores </li></ul></ul><ul><ul><ul><li>Feed mainly on plants. </li></ul></ul></ul><ul><ul><li>Carnivores </li></ul></ul><ul><ul><ul><li>Mainly eat animals that eat plants. </li></ul></ul></ul><ul><ul><li>Omnivores - Ingest both plants and animals. </li></ul></ul>Dietary Categories
  4. 4. How do Animals Obtain Food Suspension feeders – extract food particles suspended in surrounding water Substrate feeders – live in or on food source and eat their way through it Fluid feeder – gets food by sucking nutrient-rich fluids from living host Bulk feeders – Ingest large pieces of food Tube worm
  5. 5. The Four Stages of Food Processing <ul><ul><li>Ingestion </li></ul></ul><ul><ul><ul><li>Is another word for eating. </li></ul></ul></ul><ul><ul><li>Digestion </li></ul></ul><ul><ul><ul><li>Is the breakdown of food to small nutrient molecules. </li></ul></ul></ul><ul><ul><li>Absorption </li></ul></ul><ul><ul><ul><li>Is the uptake of the small nutrient molecules by cells lining the digestive tract. </li></ul></ul></ul><ul><ul><li>Elimination </li></ul></ul><ul><ul><ul><li>Is the disposal of undigested materials from the food we eat. </li></ul></ul></ul>
  6. 6. Digestion: A Closer Look <ul><ul><li>Mechanical digestion </li></ul></ul><ul><ul><ul><li>Begins the process. </li></ul></ul></ul><ul><ul><ul><li>Involves physical processes like chewing. </li></ul></ul></ul><ul><ul><li>Chemical digestion </li></ul></ul><ul><ul><ul><li>Is the chemical breakdown of food by digestive enzymes. </li></ul></ul></ul><ul><ul><li>Digestion </li></ul></ul><ul><ul><ul><li>Dismantles food particles for use by the body. </li></ul></ul></ul>
  7. 7. Digestive Compartments <ul><ul><li>In animals, chemical digestion is contained safely within some kind of compartment. </li></ul></ul><ul><ul><li>Food vacuoles – simplest digestive compartment </li></ul></ul><ul><ul><ul><li>Are intracellular organelles filled with digestive enzymes. </li></ul></ul></ul><ul><ul><li>Gastrovascular cavities are </li></ul></ul><ul><ul><li>compartments with a single opening. </li></ul></ul><ul><ul><li>Digestive tubes have two separate openings, a mouth and an anus. </li></ul></ul>Specialized organs are along the length to perform 4 main functions of food processing
  8. 8. A Tour of the Human Digestive System System Map <ul><ul><li>The human digestive system consists of: </li></ul></ul><ul><ul><ul><li>A digestive tube, the alimentary canal </li></ul></ul></ul><ul><ul><ul><li>Accessory organs that secrete digestive chemicals </li></ul></ul></ul>Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
  9. 9. <ul><ul><li>Food processing takes place along the alimentary canal. </li></ul></ul>
  10. 10. The Mouth <ul><ul><li>The mouth, or oral cavity, </li></ul></ul><ul><ul><ul><li>Functions in ingestion and the preliminary steps of digestion </li></ul></ul></ul><ul><ul><ul><ul><li>Mechanical – teeth tear and grind food </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Chemical – amylase in saliva breaks down starch </li></ul></ul></ul></ul>
  11. 11. The Pharynx <ul><ul><ul><li>Connects the mouth to the esophagus. </li></ul></ul></ul><ul><ul><ul><li>Also opens to the trachea (windpipe) </li></ul></ul></ul><ul><ul><li>During swallowing, a reflex tips the epiglottis to close the windpipe entrance. </li></ul></ul>
  12. 12. The Esophagus <ul><ul><li>The esophagus </li></ul></ul><ul><ul><ul><li>Is a muscular tube. </li></ul></ul></ul><ul><ul><ul><li>Connects the pharynx to the stomach. </li></ul></ul></ul><ul><ul><ul><li>Moves food down by peristalsis </li></ul></ul></ul><ul><ul><ul><li>Peristalsis – rhythmic waves of muscular </li></ul></ul></ul><ul><ul><ul><li>contractions. </li></ul></ul></ul>
  13. 13. The Stomach <ul><ul><li>The stomach </li></ul></ul><ul><ul><ul><li>Can store food for several hours – can store up to 2L or half gallon </li></ul></ul></ul><ul><li>- Chemical digestion – gastric juice has </li></ul><ul><li>mucus, enzymes, and acid </li></ul><ul><ul><ul><li>-Churns food into a thick soup called acid chyme. </li></ul></ul></ul><ul><ul><ul><li>-Sphincter regulates transfer of chyme from stomach to small intestine </li></ul></ul></ul><ul><li>What protects the stomach lining? </li></ul><ul><li>-Pepsin is secreted in the inactive form of pepsinogen </li></ul><ul><li>-Mucus </li></ul><ul><li>-Gastric juice is not secreted constantly. It is regulated by nerves </li></ul><ul><li>-Mitosis </li></ul>
  14. 14. The Process of Science: How Does the Stomach Work? <ul><ul><li>The accidental shooting of a man in 1822 </li></ul></ul><ul><ul><ul><li>Provided an opportunity for a doctor named William Beaumont to learn about the stomach’s many functions. </li></ul></ul></ul>Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
  15. 15. Stomach Ailments <ul><ul><li>Gastric ulcers </li></ul></ul><ul><ul><ul><li>Are erosions of the stomach lining. </li></ul></ul></ul><ul><ul><ul><li>Are often caused by a bacterium named Helicobacter pylori . </li></ul></ul></ul>Acid Reflux (“Heart burn”) – backflow of chyme into lower end of esophagus.
  16. 16. The Small Intestine <ul><ul><li>The small intestine </li></ul></ul><ul><ul><ul><li>Is the longest part of the alimentary canal (20ft). </li></ul></ul></ul><ul><ul><ul><li>Is the major organ for chemical digestion and absorption. </li></ul></ul></ul><ul><ul><ul><li>Hydrolases break down food to monomers. </li></ul></ul></ul><ul><ul><li>. </li></ul></ul><ul><ul><li>The duodenum – (first part of intestine) </li></ul></ul><ul><ul><ul><li>Receives digestive agents from several organs. </li></ul></ul></ul><ul><ul><li>Contributing organs to digestion in small intestine are: </li></ul></ul><ul><ul><li>1 - The pancreas </li></ul></ul><ul><ul><ul><li>Secretes juice that neutralizes stomach acids into the duodenum. </li></ul></ul></ul><ul><ul><li>2 - The liver </li></ul></ul><ul><ul><ul><li>Secretes bile which is stored in the gall bladder. Helps digest fats. </li></ul></ul></ul>Bile has salts that bind to fat preventing them from reforming large globules. Helps lipase work on them more efficiently.
  17. 17. Absorption of Nutrients <ul><ul><li>Although food has been ingested, </li></ul></ul><ul><ul><ul><li>It is not technically “in” the body yet. </li></ul></ul></ul><ul><ul><ul><li>It must be absorbed. </li></ul></ul></ul><ul><ul><li>The jejunum and ileum </li></ul></ul><ul><ul><ul><li>Are parts of the small intestine specialized for absorption. </li></ul></ul></ul><ul><ul><li>The intestinal wall </li></ul></ul><ul><ul><ul><li>Contains villi and </li></ul></ul></ul><ul><ul><ul><li>microvilli , which provide </li></ul></ul></ul><ul><ul><ul><li>a large surface area for </li></ul></ul></ul><ul><ul><ul><li>absorption (tennis court size) </li></ul></ul></ul>
  18. 18. The Large Intestine (and Beyond) <ul><ul><li>The large intestine or colon </li></ul></ul><ul><ul><ul><li>Is shorter, but wider, than the small intestine. </li></ul></ul></ul><ul><ul><ul><li>Makes up most of the length of the large intestine. </li></ul></ul></ul><ul><ul><ul><li>Absorbs water from the alimentary canal. </li></ul></ul></ul><ul><ul><ul><li>Produces feces, the waste product of food. </li></ul></ul></ul>Cecum <ul><ul><li>The rectum </li></ul></ul><ul><ul><ul><li>Is the last 15 cm (6 inches) of the large intestine. </li></ul></ul></ul><ul><ul><ul><li>Store feces until it can be eliminated. </li></ul></ul></ul><ul><ul><li>The anus </li></ul></ul><ul><ul><ul><li>Regulates opening of rectum. </li></ul></ul></ul><ul><ul><ul><li>Expels feces. </li></ul></ul></ul>
  19. 19. Human Nutritional Requirements <ul><ul><li>Proper nutrition helps to maintain homeostasis. </li></ul></ul><ul><ul><li>A balanced diet provides </li></ul></ul><ul><ul><ul><li>Fuel energy for cellular work. </li></ul></ul></ul><ul><ul><ul><li>Building materials to construct needed materials. </li></ul></ul></ul>
  20. 20. Food as Fuel <ul><ul><li>Cells </li></ul></ul><ul><ul><ul><li>Break down food molecules in cellular respiration. </li></ul></ul></ul><ul><ul><ul><li>Generate many molecules of ATP. </li></ul></ul></ul><ul><ul><li>Calories are </li></ul></ul><ul><ul><ul><li>A measure of the energy stored in your food. </li></ul></ul></ul><ul><ul><ul><li>A measure of the energy you expend in daily activities. (1kcal = 1000 calories) </li></ul></ul></ul>
  21. 21. Metabolic Rate – How fast do we burn our food? <ul><ul><li>The metabolic rate of an organism is the rate of energy consumption per day. </li></ul></ul><ul><ul><li>If we take in more than our cells can use it is stored (glycogen, fat) </li></ul></ul><ul><ul><li>MR also depends on body size, stress level, age, heredity </li></ul></ul>
  22. 22. Food as Building Material <ul><ul><li>The cells of your body </li></ul></ul><ul><ul><ul><li>Assemble polymers from the monomers found in food. </li></ul></ul></ul><ul><ul><li>Essential nutrients </li></ul></ul><ul><ul><ul><li>Are substances needed by the body that it cannot make itself. </li></ul></ul></ul><ul><ul><li>Malnutrition results from a long term dietary deficiency of one or more of the essential nutrients. </li></ul></ul><ul><ul><ul><li>Protein deficiency is an example. </li></ul></ul></ul>- Kwashiorkor is caused by inadequate protein intake. -This causes deficiency in the blood protein, manifesting in the swelling of belly and limbs <ul><ul><li>Undernutrition </li></ul></ul><ul><ul><ul><li>Is caused by inadequate intake of nutrients. </li></ul></ul></ul><ul><ul><ul><li>Body begins breaking down its own molecules (including brain and muscles). </li></ul></ul></ul>Scurvy – Lack of vitamin C
  23. 23. Essential Amino Acids <ul><ul><li>There are eight essential amino acids. </li></ul></ul><ul><ul><ul><li>Different foods contain different ones. </li></ul></ul></ul>
  24. 24. Vitamins <ul><ul><li>Vitamins </li></ul></ul><ul><ul><ul><li>Are organic molecules required in the diet for good health. </li></ul></ul></ul><ul><ul><ul><li>Need less than the essential amino acids </li></ul></ul></ul><ul><ul><ul><li>Function mostly as assistants to enzymes by catalyzing metabolic reactions. </li></ul></ul></ul>
  25. 25. Minerals <ul><ul><li>Minerals </li></ul></ul><ul><ul><ul><li>Are inorganic substances required in the diet </li></ul></ul></ul><ul><ul><ul><li>Deficiency can cause health problems </li></ul></ul></ul><ul><ul><ul><li>(Ex. Calcium – degenerative bone disease) </li></ul></ul></ul>
  26. 26. Essential Fatty Acids <ul><ul><li>Our cells make fats and other lipids by combining fatty acids with other molecules. </li></ul></ul><ul><ul><li>Essential fatty acids are the fatty acids we cannot make from simpler molecules (omega 3 and omega 6). </li></ul></ul><ul><ul><li>Function (to name a few): </li></ul></ul><ul><ul><ul><li>Affects infl ammation and many other cellular functions </li></ul></ul></ul><ul><ul><ul><li>Affecting mood and behavior </li></ul></ul></ul><ul><ul><ul><li>Affecting cellular signaling) [2] </li></ul></ul></ul>
  27. 27. Figure 22.24 Remember, the best way to maintain a healthy weight is to eat a balanced diet and get plenty of exercise.