© 2013 Pearson Education, Inc. Lectures by Edward J. Zalisko PowerPoint ® Lectures for Campbell Essential Biology, Fifth Edition, and Campbell Essential Biology with Physiology, Fourth Edition – Eric J. Simon, Jean L. Dickey, and Jane B. Reece Chapter 22 Nutrition and Digestion

Biology and Society: The “Secret” to Shedding Pounds About 50 million Americans go on a diet each year. –Weight loss is a growing industry. –Yet only about 5% of dieters are able to reach their goal weight and maintain it for the long term. © 2013 Pearson Education, Inc.

Figure 22.0

More than a third of American adults are obese (very overweight). Obesity is estimated to contribute to 300,000 deaths per year in the United States. The United Nations World Health Organization recognizes obesity as a major global health problem. Biology and Society: The “Secret” to Shedding Pounds

There really is no trick to managing your weight. –Add up the calories from the food you eat. –Subtract the calories that your body burns. –If you take in more than you burn, you will gain weight. –If you burn more than you take in, you will lose weight. Biology and Society: The “Secret” to Shedding Pounds

OVERVIEW OF ANIMAL NUTRITION Food provides the raw materials that animals, including people, need to –build tissue and –fuel cellular work. © 2013 Pearson Education, Inc.

Animal Diets Herbivores mainly feed on plants or algae. Carnivores mainly eat other animals. Omnivores eat –animals and –plants or algae. © 2013 Pearson Education, Inc.

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

The Four Stages of Food Processing Ingestion is another word for eating. Digestion is the breakdown of food into molecules small enough for the body to absorb. Absorption is the uptake of the small nutrient molecules by cells lining the digestive tract. Elimination is the disposal of undigested materials left over from food. © 2013 Pearson Education, Inc.

Digestion: A Closer Look The dismantling of food molecules is necessary because food molecules are –too large to cross the membranes of animal cells and –different from molecules that make up an animal’s body. © 2013 Pearson Education, Inc.

Mechanical digestion –begins the process and –involves physical processes like chewing. Chemical digestion is the chemical breakdown of food by digestive enzymes. Digestion: A Closer Look © 2013 Pearson Education, Inc.

Figure 22.2 Cheese protein (a polymer of amino acids in a specific sequence) Amino acid monomer Amino acids Human protein Breakdown of protein by human digestive system Absorption of amino acids by cells lining the small intestine; transport via bloodstream to other cells Cells use amino acids from the cheese and other foods to produce new human proteins 123

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. Digestion: A Closer Look © 2013 Pearson Education, Inc.

Figure 22.3a-2 Enzyme (pepsin) Protein H2OH2O Amino acid H OH

Figure 22.3b-2 Enzyme (amylase) Carbohydrate Sugar H2OH2O H OH

Figure 22.3c-2 Enzyme (lipase) Fat Fatty acid Glycerol H2OH2O H2OH2O H2OH2O OH H H H

Digestive Compartments How do animals digest their food without digesting themselves? In animals, chemical digestion is contained safely within some kind of compartment. © 2013 Pearson Education, Inc.

As a cell engulfs food by phagocytosis, –a food vacuole forms, –which then fuses with a lysosome filled with digestive enzymes, and –as food is digested, small food molecules pass through the vacuole membrane into the cytoplasm, which nourishes the cell. Digestive Compartments © 2013 Pearson Education, Inc.

Food vacuoles are the simplest of all digestive compartments. Sponges are the only animals that digest food solely within their cells. Gastrovascular cavities –are digestive compartments surrounded by cells and –have only a single opening. Digestive Compartments © 2013 Pearson Education, Inc.

A digestive tube, or alimentary canal, has two separate openings: –a mouth and –an anus. Digestive Compartments © 2013 Pearson Education, Inc.

Food moves through specialized regions of a digestive tube that –digest and –absorb nutrients in a stepwise fashion. Digestive Compartments © 2013 Pearson Education, Inc.

Figure 22.4a Food (water flea) Gastrovascular Cavity (compartment with single opening) Newly engulfed food particle Single opening Gastrovascular cavity Hydra Digested food particle

Figure 22.4b Interior of intestine Earthworm Intestine Mouth Anus Alimentary Canal (Digestive Tract) (tube from mouth to anus)

A TOUR OF THE HUMAN DIGESTIVE SYSTEM System Map The human digestive system consists of –a digestive tube, the alimentary canal (or gut), and –accessory organs that secrete digestive chemicals. © 2013 Pearson Education, Inc.

Figure 22.5 Oral cavity (mouth) Pharynx Esophagus Stomach Small intestine Colon of large intestine Appendix Rectum Anus Salivary glands Liver Gallbladder Pancreas Tongue ALIMENTARY CANALACCESSORY ORGANS

The Mouth The mouth, or oral cavity, functions in –ingestion and –the preliminary steps of digestion. Chemical digestion begins in the mouth with the secretion of saliva from salivary glands. © 2013 Pearson Education, Inc.

The Mouth The muscular tongue –tastes, –shapes food into a ball, and –pushes the food to the back of the mouth for swallowing. © 2013 Pearson Education, Inc.

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

The pharynx (throat) –connects the mouth to the esophagus and –opens to the trachea, which leads to the lungs. During swallowing, a reflex –moves the opening of the trachea upward and –tips the epiglottis to close the trachea entrance. The Pharynx © 2013 Pearson Education, Inc.

Figure 22.7 Epiglottis down Air flowing into open trachea (windpipe) Esophagus closed Epiglottis up Pharynx BREATHING SWALLOWING Food flowing into open esophagus Adam’s apple Trachea closed

The Esophagus The esophagus –is a muscular tube, –connects the pharynx to the stomach, and –moves food down by peristalsis, alternating waves of muscular contraction and relaxation. © 2013 Pearson Education, Inc.

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

The Stomach The stomach –can store food for several hours and –churns food into a thick soup called chyme. © 2013 Pearson Education, Inc.

Fluid in the stomach contains gastric juice, made of –strong acid, –digestive enzymes, –mucus, and –the enzyme pepsin, which digests proteins. The Stomach © 2013 Pearson Education, Inc.

Figure 22.9 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

Stomach Ailments Heartburn is caused by backflow of chyme into the esophagus. Gastric ulcers are –erosions of the stomach lining and –often caused by the bacterium Helicobacter pylori. © 2013 Pearson Education, Inc.

Weight Loss Surgeries The most common weight loss surgery in the United States is gastric bypass. –Staples are used to reduce the stomach to about the size of a chicken egg. –The first 18 inches of the small intestine are bypassed by attaching the downstream intestine directly to the reduced stomach pouch. © 2013 Pearson Education, Inc.

Weight Loss Surgeries As a result, –patients quickly feel full when eating and –the body’s ability to absorb food is reduced. © 2013 Pearson Education, Inc.

Figure Esophagus Small stomach pouch Staples New attachment Bypassed portion of stomach Tube through which food is bypassed Small intestine

The Small Intestine The small intestine is –the longest part of the alimentary canal and –the major organ for chemical digestion and absorption of nutrients into the bloodstream. © 2013 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, and –a digestive juice secreted by the intestinal lining. © 2013 Pearson Education, Inc.

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

The pancreas secretes juice that –neutralizes stomach acids in the duodenum and –aids in digestion. The liver secretes bile, which –is stored in the gallbladder and –helps digest fats. Chemical Digestion in the Small Intestine © 2013 Pearson Education, Inc.

Absorption of Nutrients In the duodenum, nutrients are –completely digested and –ready to be absorbed. Nutrients only enter the body if they are absorbed into the walls of the digestive tract. © 2013 Pearson Education, Inc.

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

Villi and microvilli on the surface of the small intestine increase –the surface area and –capacity for absorption. Absorption of Nutrients © 2013 Pearson Education, Inc.

Figure 22.13a Blood vessels Interior of intestine Muscle layers Nutrient absorption Intestinal wall Villi Interior of intestine

Figure 22.13b Nutrient absorption Epithelial cells Blood capillaries Lymphatic vessel Villi

Figure 22.13c Nutrient absorption Epithelial cells and blood capillary Microvilli Blood

The Large Intestine The large intestine is –shorter, but wider, than the small intestine and –about 1.5 meters in length. At the junction of the small and large intestine is a small, finger-like extension called the appendix. –The appendix contains white blood cells that make minor contributions to the immune system. –Appendicitis is a bacterial infection of the appendix. © 2013 Pearson Education, Inc.

The colon (large intestine) –forms the main portion of the large intestine, –absorbs water from the alimentary canal, and –produces feces, the waste product of food. The Large Intestine © 2013 Pearson Education, Inc.

The rectum –forms the last 15 cm (6 inches) of the large intestine and –stores feces until elimination. The anus –consists of two sphincters smooth and skeletal muscle and –regulates the opening of the rectum. The Large Intestine © 2013 Pearson Education, Inc.

Figure 22.14a Colon of large intestine Small intestine Rectum Anus

Figure 22.14b End of small intestine Nutrient flow Sphincter Appendix

Food processing takes place along the alimentary canal. The Large Intestine © 2013 Pearson Education, Inc.

Figure Small intestine Large intestine Stomach Mouth Anus Food Feces Digestion Mechanical digestion Chewing in mouth Churning in stomach Ingestion Food into mouth 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.UN04 Mouth (oral cavity) Digestion Absorption Chemical Mechanical Alimentary canal Accessory organs 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

HUMAN NUTRITIONAL REQUIREMENTS Proper nutrition provides –fuel for cellular work, –materials for building molecules, and –essential nutrients for health. © 2013 Pearson Education, Inc.

Food as Fuel Cells use cellular respiration to –extract energy stored in food molecules and –generate molecules of ATP to do work. © 2013 Pearson Education, Inc.

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

Calories Calories are a measure of the energy –stored in your food and –used in daily activities. © 2013 Pearson Education, Inc.

A calorie is the amount of energy required to raise the temperature of one gram of water by 1°C. A kilocalorie (kcal) is –1,000 calories, –the unit listed on food labels, and –often called Calories with an uppercase C. Calories © 2013 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, and –energy needed for activities. © 2013 Pearson Education, Inc.

Table 22.1

Food as Building Material Building blocks from the breakdown of organic molecules are used to –repair tissues and –maintain tissues. Essential nutrients –are substances needed by the body but –cannot be made in the body from other molecules. © 2013 Pearson Education, Inc.

Essential Amino Acids In humans, eight essential amino acids –must be obtained from the diet and –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 such as beans, peanuts, and peas. © 2013 Pearson Education, Inc.

Figure Complete meals Bread and peanut butter Rice and beans Rice and tofu Beans and other legumes Methionine Valine Threonine Phenylalanine Leucine Isoleucine Tryptophan Lysine

Vitamins –are organic molecules, –are required in the diet in very small amounts, and –usually assist enzymes in catalyzing metabolic reactions. Too much or too little of most vitamins can cause harm. © 2013 Pearson Education, Inc.

Table 22.2

Figure 22.UN01

Minerals Minerals are inorganic substances required in the diet. Too much or too little of most minerals can cause harm. © 2013 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. © 2013 Pearson Education, Inc.

Figure 22.UN05

Decoding Food Labels On food labels, the FDA requires –the list of ingredients and –key nutrition facts. © 2013 Pearson Education, Inc.

Figure 22.18

Figure 22.UN06 Nutrition Facts Serving Size 1 Cookie  28 g/1 oz  Servings Per Container 8 Calories 140 Calories from Fat 60 Total Fat 7g Cholesterol 10mg Sodium 80mg Total Carbohydrate 18g Protein 2g Saturated Fat 3g Trans Fat 0g Dietary Fiber 1g Sugars 10g % Daily Value* 11% 15% 3% 6% 4% Amount Per Serving

NUTRITIONAL DISORDERS Dietary problems can cause severe health problems. © 2013 Pearson Education, Inc.

Malnutrition Malnutrition refers to health problems caused by an –improper or –insufficient diet. Protein deficiency –causes the most human suffering and –is concentrated where there is a great gap between food supply and population size. © 2013 Pearson Education, Inc.

Figure 22.19

Eating Disorders Eating disorders –affect millions of Americans, –are more common in women than men, and –result in malnutrition. © 2013 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. Eating Disorders © 2013 Pearson Education, Inc.

Obesity –is a too-high body mass index (BMI), –is the nutritional disorder of greatest concern, –affects about one-third of all Americans, and –increases the risk of heart attack, diabetes, and other diseases. © 2013 Pearson Education, Inc.

Figure Weight (pounds) Height Underweight Normal Overweight Obese Extremely obese 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” BMI <18.5 BMI 18.5–24 BMI 25–29 BMI 30–39 BMI >

Figure 22.21

Evolution Connection: Fat and Sugar Cravings Most Americans –crave fatty and/or sweet foods and –eat too many high-calorie foods. A feast-or-famine existence in our ancestors may have favored individuals who gorged themselves on the rare occasions when rich, fatty foods were available. © 2013 Pearson Education, Inc.

Figure 22.23