1. © 2010 Pearson Education, Inc. Lectures by Chris C. Romero, updated by Edward J. Zalisko PowerPoint ® Lectures for Campbell Essential Biology, Fourth Edition – Eric Simon, Jane Reece, and Jean Dickey Campbell Essential Biology with Physiology, Third Edition – Eric Simon, Jane Reece, and Jean Dickey Chapter 22 Nutrition and Digestion

2. © 2010 Pearson Education, Inc. OVERVIEW OF ANIMAL NUTRITION Animals must feed on other organisms to acquire nutrients.

3. © 2010 Pearson Education, Inc. Animal Diets Herbivores mainly feed on plants. Carnivores eat animals. Omnivores eat plants and animals. Video: Shark Eating a Seal Video: Lobster Mouth Parts

4. Herbivore (mainly eats plants or algae) Carnivore (mainly eats animals) Omnivore (regularly eats animals as well as plants or algae) ANIMAL DIETS Figure 22.1

5. © 2010 Pearson Education, Inc. The Four Stages of Food Processing Ingestion is another word for eating. Digestion is the breakdown of food to small nutrient molecules.

6. © 2010 Pearson Education, Inc. Absorption is the uptake of the small nutrient molecules by cells lining the digestive tract. Elimination is the disposal of undigested materials from the food we eat.

7. © 2010 Pearson Education, Inc. Digestion: A Closer Look Mechanical digestion –Begins the process –Involves physical processes like chewing Chemical digestion is the chemical breakdown of food by digestive enzymes.

8. © 2010 Pearson Education, Inc. Digestion dismantles food to create: –Molecules small enough for cells to absorb –Monomers that can be recombined into new molecules

9. Cheese protein (a polymer of amino acids in a specific sequence) Breakdown of protein by human digestive system Amino acid monomer Amino acids Absorption of amino acids by cells lining the small intestine; transport via bloodstream to other cells Human protein Cells use amino acids from the cheese and other foods to produce new human proteins Figure 22.2-3

10. © 2010 Pearson Education, Inc. Chemical digestion proceeds via hydrolysis, chemical reactions that break down polymers into monomers using water in the process. Like most biological reactions, digestion also requires enzymes.

11. Enzyme (pepsin) Enzyme (amylase) Enzyme (lipase) Protein Carbohydrate Fat Amino acid Fatty acid Glycerol Sugar H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H OH H H H H Figure 22.3

12. © 2010 Pearson Education, Inc. Digestive Compartments How do animals digest their food without digesting themselves? In animals, chemical digestion is contained safely within some kind of compartment.

13. © 2010 Pearson Education, Inc. Food vacuoles are: –Intracellular organelles filled with digestive enzymes –The simplest of all digestive compartments –Used by sponges as the only way to digest food

14. © 2010 Pearson Education, Inc. Gastrovascular cavities: –Are digestive compartments surrounded by cells –Have only a single opening Video: Hydra Eating Daphnia

15. Food (water Flea) Alimentary Canal (Digestive Tract) Gastrovascular Cavity MAIN TYPES OF DIGESTIVE COMPARTMENTS Interior of intestine Food particle engulfed Single opening Gastrovascular cavity Earthworm Intestine Mouth Hydra Anus Figure 22.4

16. © 2010 Pearson Education, Inc. Digestive tubes have two separate openings: –A mouth –An anus

17. A TOUR OF THE HUMAN DIGESTIVE SYSTEM System Map The human digestive system consists of: –A digestive tube, the alimentary canal –Accessory organs that secrete digestive chemicals © 2010 Pearson Education, Inc.

18. Salivary glands Liver Gallbladder Pancreas Mouth Tongue Pharynx Esophagus Stomach Small intestine Colon of large intestine Appendix Rectum Anus ACCESSORY ORGANS ALIMENTARY CANAL Figure 22.5

19. © 2010 Pearson Education, Inc. The Mouth The mouth, or oral cavity, functions in: –Ingestion –The preliminary steps of digestion

20. Incisors Canine Premolars Molars “Wisdom” tooth Tongue Opening of a salivary gland duct Teeth Figure 22.6

21. © 2010 Pearson Education, Inc. The Pharynx The pharynx: –Connects the mouth to the esophagus –Opens to the trachea, which leads to the lungs

22. © 2010 Pearson Education, Inc. During swallowing, a reflex: –Tips the epiglottis –Closes the entrance to the windpipe

23. Esophageal sphincter (contracted) Trachea (windpipe) open Esophagus closed Epiglottis up Ball of food Pharynx Tongue NOT SWALLOWINGSWALLOWING STARTED Epiglottis down Esophagus open Trachea closed Adam’s apple SWALLOWING FINISHED Epiglottis up Trachea open Esophageal sphincter (contracted) Figure 22.7-3

24. © 2010 Pearson Education, Inc. The Esophagus The esophagus: –Is a muscular tube –Connects the pharynx to the stomach –Moves food down by peristalsis, alternating waves of muscular contraction and relaxation

25. Esophageal sphincter (contracted) Contracted muscles Relaxed muscles Food ball Stomach Figure 22.8

26. © 2010 Pearson Education, Inc. The Stomach The stomach: –Can store food for several hours –Churns food into a thick soup called chyme

27. © 2010 Pearson Education, Inc. Fluid in the stomach contains gastric juice, made of: –Strong acid –Digestive enzymes –Mucus –The enzyme pepsin, which digests proteins

28. Stomach lining secretes gastric juice (acid, enzyme molecules, and mucus). Sphincters control the flow into and out of the stomach. Accordion-like folds allow the stomach to expand. Food particle Small intestine Esophagus Figure 22.9

29. © 2010 Pearson Education, Inc. Stomach Ailments Heartburn is caused by backflow of chyme into the esophagus. Gastric ulcers are: –Erosions of the stomach lining –Often caused by the bacterium Helicobacter pylori

30. Stomach mucusHelicobacter pylori bacteria Colorized SEM Figure 22.10

31. © 2010 Pearson Education, Inc. The Small Intestine The small intestine is: –The longest part of the alimentary canal –The major organ for chemical digestion and absorption of nutrients into the bloodstream

32. © 2010 Pearson Education, Inc. Chemical Digestion in the Small Intestine Most chemical digestion occurs in the duodenum, the first part of the small intestine. In the duodenum, chyme from the stomach mixes with: –Pancreatic juice –Bile –A digestive juice secreted by the intestinal lining

33. Liver Gallbladder Bile Chyme Stomach Pancreas Pancreatic juice Duodenum of small intestine Intestinal enzymes Figure 22.11

34. © 2010 Pearson Education, Inc. The pancreas secretes juice that neutralizes stomach acids in the duodenum. The liver secretes bile, which: –Is stored in the gallbladder –Helps digest fats

35. © 2010 Pearson Education, Inc. Absorption of Nutrients In the duodenum, nutrients are: –Completely digested –Ready to be absorbed Nutrients only enter the body if they are absorbed into the walls of the digestive tract.

36. Food through the alimentary canalA finger through a hole Alimentary canal Mouth Anus Figure 22.12

37. © 2010 Pearson Education, Inc. Villi and microvilli on the surface of the small intestine increase: –The surface area –Capacity for absorption

38. Blood vessels Interior of intestine Interior of intestine Muscle layers Nutrient absorption Nutrient absorption Nutrient absorption Epithelial cells Blood capillaries Lymphatic vessel Epithelial cells and blood capillary Intestinal wall Microvilli Villi Blood Villi Figure 22.13

39. © 2010 Pearson Education, Inc. The Large Intestine The large intestine is: –Shorter, but wider, than the small intestine –About 1.5 meters in length

40. © 2010 Pearson Education, Inc. The colon: –Forms the main portion of the large intestine –Absorbs water from the alimentary canal –Produces feces, the waste product of food

41. © 2010 Pearson Education, Inc. The rectum: –Forms the last 15 cm (6 inches) of the large intestine –Stores feces until elimination The anus: –Consists of two sphincters –Regulates the opening of the rectum

42. Colon of large intestine End of small intestine Small intestine Nutrient flow Sphincter Appendix Rectum Anus Figure 22.14

43. © 2010 Pearson Education, Inc. Food processing takes place along the alimentary canal.

44. Ingestion Food into mouth Small intestine Large intestine Stomach Mouth Anus Food Digestion Mechanical digestion Chewing in mouth Churning in stomach Chemical digestion Saliva in mouth Acid and pepsin in stomach Enzymes in small intestine Absorption Nutrients and water in small intestine Water in large intestine Elimination Feces formed in large intestine Elimination from anus Figure 22.15-4

45. © 2010 Pearson Education, Inc. HUMAN NUTRITIONAL REQUIREMENTS Proper nutrition helps maintain homeostasis. A balanced diet provides: –Fuel for cellular work –Materials for building molecules –Essential nutrients for health

46. © 2010 Pearson Education, Inc. Food as Fuel Cells use cellular respiration to: –Extract energy stored in food molecules –Generate molecules of ATP to do work

47. Cellular respiration Mitochondrion Cell O2O2 ATP and  energy for cellular work  “Exhaust” H2OH2O CO 2 “Fuel” (organic molecules such as glucose) C 6 H 12 O 6 Figure 22.16-2

48. © 2010 Pearson Education, Inc. Calories Calories are a measure of the energy: –Stored in your food –Used in daily activities

49. © 2010 Pearson Education, Inc. A calorie is the amount of energy required to raise the temperature of one gram of water by 1ºC. A kilocalorie (kcal) is: –One thousand calories –The unit listed on food labels –Often called Calories with an uppercase C

50. © 2010 Pearson Education, Inc. Metabolic Rate The rate of energy consumption by the body is the metabolic rate. A person’s metabolic rate consists of: –The basal metabolic rate (BMR), the amount of energy it takes to maintain body functions –Energy needed for activities

51. Table 22.1

52. © 2010 Pearson Education, Inc. Food as Building Material Building blocks from the breakdown of organic molecules are used to: –Repair tissues –Maintain tissues Essential nutrients: –Are substances needed by the body but –Cannot be made in the body from other molecules

53. © 2010 Pearson Education, Inc. Essential Amino Acids In humans, eight essential amino acids: –Must be obtained from the diet –Are in different proportions in different foods All eight essential amino acids can be consumed by eating: –Meat, eggs, or milk or –A variety of plants, typically grains and legumes

54. Complete meals Essential amino acids Bread and peanut butterRice and beansRice and tofu Corn Beans and other legumes Methionine Valine Threonine Phenylalanine Leucine Isoleucine Tryptophan Lysine Figure 22.17

55. © 2010 Pearson Education, Inc. Vitamins Vitamins: –Are organic molecules –Are required in the diet in very small amounts –Usually assist enzymes in catalyzing metabolic reactions

56. © 2010 Pearson Education, Inc. Too much or too little of most vitamins can cause harm.

57. Table 22.2

58. © 2010 Pearson Education, Inc. Minerals Minerals are inorganic substances required in the diet. Too much or too little of most minerals can cause harm.

59. © 2010 Pearson Education, Inc. Essential Fatty Acids Our cells make fats and other lipids by combining fatty acids and other molecules. Essential fatty acids must be obtained in the diet.

60. © 2010 Pearson Education, Inc. Decoding Food Labels On food labels, the FDA requires: –The list of ingredients –Key nutrition facts

61. Figure 22.18

62. © 2010 Pearson Education, Inc. NUTRITIONAL DISORDERS Nutritional dysfunction can cause severe problems.

63. © 2010 Pearson Education, Inc. Malnutrition Malnutrition refers to health problems caused by an: –Improper or –Insufficient diet Protein deficiency: –causes the most human suffering –Is concentrated where there is a great gap between food supply and population size

64. Figure 22.19

65. © 2010 Pearson Education, Inc. Eating Disorders Eating disorders: –Affect millions of Americans –Are more common in women than men –Result in malnutrition

66. © 2010 Pearson Education, Inc. Anorexia nervosa is self-starvation, even when a person is underweight. Bulimia involves: –Binge eating –Purging through induced vomiting –Abuse of laxatives, and/or –Excessive exercise

67. © 2010 Pearson Education, Inc. Obesity Obesity: –Is an inappropriately high body mass index (BMI) –Is the nutritional disorder of greatest concern –Affects about one-third of all Americans –Increases the risk of heart attack, diabetes, and other diseases

68. Weight (pounds) Height Underweight BMI <18.5 Normal BMI 18.5–24 Overweight BMI 25–29 Obese BMI 30–39 Extremely obese BMI >39 6’4” 6’3” 6’2” 6’1” 6’0” 5’11” 5’10” 5’9” 5’8” 5’7” 5’6” 5’5” 5’4” 5’3” 5’2” 5’1” 5’0” 4’11” 4’10” 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 Figure 22.20

69. The Process of Science: Can a Gene Make You Fat? Observation: A mutation in a particular gene in mice leads to a significant increase in body fat. Question: How does a small change in DNA cause such a large change in the body? Hypothesis: The mutant mice become overweight because their obese gene fails to produce a protein called leptin. © 2010 Pearson Education, Inc.

70. Experiment: Mutant and normal mice were injected with leptin or a saline control. Results: Mutant mice that received leptin ended the study weighing about half as much as mutant mice that received the saline control. Over 100 genes are known to contribute to weight maintenance in humans. Genetics only partially explains why weight control can be difficult.

71. Figure 22.21

72. Ending body mass (g) Mutant mice with defective obese gene Mice with normal obese gene Injected with saline Injected with leptin 0 10 20 30 40 50 60 Figure 22.22

73. Evolution Connection: Fat and Sugar Cravings Most Americans: –Crave fatty and/or sweet foods –Eat too many high-calorie foods A feast-or-famine existence in our ancestors may have favored individuals who gorged themselves on rich, fatty foods. © 2010 Pearson Education, Inc.

74. Figure 22.23

75. Ingestion Food Food in mouth Digestion Mechanical digestion Chemical digestion via enzymes Small molecules Inside body Absorption Elimination Undigested materials Figure 22.UN1-4

76. Mouth (oral cavity) Pharynx and esophagus Stomach Small intestine Large intestine Anus Salivary glands Liver, gallbladder, pancreas Chewing Churning Salivary amylase Acid and pepsin (in gastric juice) Other enzymes Nutrients and water Water Alimentary canal Accessory organs Digestion MechanicalChemical Absorption Figure 22.UN2

77. Cell Food O2O2 Cellular respiration H2OH2O CO 2 ATP Figure 22.UN3-2

78. Essential Amino Acids Essential Fatty Acids MineralsVitamins Required for protein production Organic molecules required in very small amounts Essential chemical elements from inorganic compounds Required to make cell membranes ESSENTIAL NUTRIENTS Figure 22.UN4