营养和消化 大学生物 Nutrition and Digestion

Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,Chapter 21,Nutrition and Digestion,0,0,Introduction,All animals must eat to provide,energy and,the building blocks used to assemble (,組合,) new molecules.,Animals also need essential,vitamins and,minerals.,0,Introduction,The modern human diet in developed countries allows access to relatively cheap and available calorie-dense foods.,This diet, combined with sedentary (,坐,),jobs and inactive lifestyles, has led to an obesity crisis in the United States leading to,68% of people categorized as overweight and,100 million (,十億,) people categorized as obese.,Thus, the modern diet appears to be contributing to shorter, less healthy lives.,Chapter 21: Big Ideas,Nutrition,Obtaining andProcessing Food,The HumanDigestive System,0,OBTAINING AND PROCESSING FOOD,0,21.1 Animals obtain and ingest their food in a variety of ways,Most animals have one of three kinds of diets.,Herbivores,(,草食,),eat plants and include cattle(,家牛,), snails, and sea urchins (,海膽,).,Carnivores,(,肉食,),eat meat and include lions, hawks, and spiders.,Omnivores (,雜食,),eat plants and other animals and include humans, roaches(,蟑螂,), raccoons(,浣熊,), and crows (,烏鴉,).,0,Animals obtain and ingest their food in different ways.,Suspension feeders (,懸浮物攝食者,),sift (,過濾,) small organisms or food particles from water.,Substrate feeders (,基質攝食者,),live in or on their food source and eat their way through it.,Fluid feeders (,流體攝食者,),suck nutrient-rich fluids from a living host.,Bulk feeders (,大塊攝食者,),ingest large pieces of food.,21.1 Animals obtain and ingest their food in a variety of ways,管蠕蟲,Caterpillar,Feces,蒼鷺,0,21.2 Overview: Food processing occurs in four stages,Food is processed in four stages.,Ingestion (,攝食,),is the act of eating.,Digestion,(,消化,),is the breaking down of food into molecules,small,enough for the body to absorb.,Absorption (,吸收,),is the take-up of the products of digestion, usually by the cells lining (,內襯,) the digestive tract.,Elimination (,排除,),is the removal of undigested materials out of the digestive tract.,Mechanicaldigestion,Piecesof food,Smallmolecules,Chemicaldigestion(hydrolysis),Nutrientmoleculesenter bodycells,Undigestedmaterial,Ingestion,Digestion,Absorption,Elimination,3,4,2,1,Food Molecules,Components,Protein,Protein-digestingenzymes,Carbohydrate-digestingenzymes,Nucleic-acid-digestingenzymes,Fat-digestingenzymes,Amino acids,Polysaccharide,Disaccharide,Monosaccharides,Nucleic acid,Nucleotides,Fat,Glycerol,Fatty acids,(,核苷酸,),0,21.3 Digestion occurs in specialized compartments,Sponges (,海綿,) digest food in vacuoles (,液泡,).,Most animals digest food in compartments (,室,).,Cnidarians(,腔腸動物,)and flatworms(,扁蟲,) have a,gastrovascular cavity(,消化循環腔,),with a single opening, the,mouth,.,Food enters the mouth.,Enzymes break down the food.,Food particles move into cells lining the compartment.,Undigested materials are expelled back out the mouth.,0,Most animals have an,alimentary canal (,消化道,),with,a mouth,an anus, and,specialized regions associated with one-way flow of food.,21.3 Digestion occurs in specialized compartments,0,The normal one-way flow moves food,into the,pharynx (,咽,),or throat,down the,esophagus (,食道,),to a,crop (,嗉囊,),where food is softened and stored,gizzard (,砂囊,), where food is ground (,磨碎,) and stored, and/or,stomach (,胃,),where food is ground and stored,to the,intestines, where chemical digestion and nutrient absorption occur, and finally,undigested materials are expelled through the,anus(,肛門,),.,21.3 Digestion occurs in specialized compartments,Tentacles,3,1,2,4,Mouth,Food(a water flea),Gastrovascularcavity,Digestive enzymesbeing released froma gland cell,Food digested tosmall particles,A food particlebeing engulfed,A food particledigested in afood vacuole,hydra(,水螅,),(,吞入,),Earthworm,Mouth,Pharynx,Esophagus,Crop,Gizzard,Intestine,Anus,Grasshopper,Esophagus,Esophagus,Bird,Mouth,Mouth,Crop,Crop,Gizzard,Stomach,Intestine,Anus,Anus,Midgut,Hindgut,Gastricpouches,嗉,囊,砂囊,後腸,中腸,胃囊,咽,0,THE HUMAN DIGESTIVE SYSTEM,0,21.4 The human digestive system consists of an alimentary canal and accessory glands,In humans, food is,ingested and chewed in the mouth or,oral cavity,pushed by the tongue into the pharynx,moved along by alternating waves of contraction and relaxation by smooth muscle in the walls of the canal in a process called,peristalsis (,蠕動,), and,moved in and out of the stomach by,sphincters (,括約肌,),.,0,21.4 The human digestive system consists of an alimentary canal and accessory glands,The final steps of digestion and nutrient absorption in humans occur in the small intestine.,Undigested materials move through the large intestine, feces are stored in the rectum(,直腸,), and then expelled out the anus.,Key,Alimentary canal,Accessory digestiveglands,Rectum,Anus,Smallintestine,Largeintestine,Stomach,Esophagus,Oralcavity,A schematic diagram of thehuman digestive system,Salivaryglands,Gall-bladder,Liver,Pancreas,膽囊,Esophagus,Pharynx,Esophagus,Sphincters,Stomach,Small intestine,Nasal cavity,Oral cavity(mouth),Tongue,Smallintestine,Largeintestine,Rectum,Anus,Salivaryglands,Gall-bladder,Liver,Pancreas,0,21.5 Digestion begins in the oral cavity,Mechanical digestion and chemical digestion begin in the mouth.,Chewing cuts, smashes, and grinds food, making it easier to swallow.,The tongue,tastes,shapes the food into a ball called a,bolus(,食團,), and,moves it toward the pharynx.,0,21.5 Digestion begins in the oral cavity,Salivary glands (,唾液腺,),release,a slippery glycoprotein(,糖蛋白,) that moistens,(,濡濕,) and lubricates (,潤滑,) food for easier swallowing,buffers (,緩衝,) that neutralize acids,salivary enzyme amylase(,澱粉酶,) that begins the hydrolysis of starch, and,antibacterial agents that kill some bacteria ingested with food.,Incisors,Canine,Premolars,Molars,“Wisdom”tooth,Tongue,Salivaryglands,Opening ofa salivarygland duct,門牙,犬齒,前臼齒,臼齒,智齒,0,21.6 After swallowing, peristalsis moves food through the esophagus to the stomach,Air moves from the pharynx,into the larynx,past the vocal cords in the voice box,into the trachea, and,into the lungs.,0,21.6 After swallowing, peristalsis moves food through the esophagus to the stomach,Swallowed food and drink move from the pharynx,into the esophagus, and,into the stomach.,During swallowing,the tip of the larynx (,喉,) moves upward,preventing the food from entering the trachea.,Swallowing reflex(sphincter relaxed),Epiglottis down,Larynx up,會厭,Swallowing completed(sphincter contracted),Epiglottis up,Larynx down,Esophageal sphincter(contracted),Bolus offood,Muscles contract,squeezing the bolusthrough the esophagus.,Muscles relax,allowing thepassagewayto open.,Bolus offood,Stomach,0,21.7 CONNECTION: The Heimlich maneuver can save lives,The Heimlich maneuver(,哈姆立克,氏,急救法,),involves a forceful elevation of the diaphragm(,橫膈膜,),pushes air into the trachea, and,can dislodge (,移動,) food from the pharynx or trachea during choking (,窒息,).,Brain damage will occur within minutes if no airway is open.,0,21.8 The stomach stores food and breaks it down with acid and enzymes,The stomach can stretch and store up to 2 liters of food and drink.,Some chemical digestion occurs in the stomach.,The stomach secretes,gastric juice(,胃液,), made up of,Mucus (,粘液,),a protein-digesting enzyme, and,strong acid with a pH of about 2 that,kills ingested bacteria,breaks apart cells in food, and,denatures proteins.,0,21.8 The stomach stores food and breaks it down with acid and enzymes,Pepsinogen (,胃蛋白酶原,)and HCl produce active pepsin(,胃蛋白酶,).,Pepsinogen, H,+, and Cl,are secreted into the lumen (,內腔,) of the stomach.,HCl converts some pepsinogen to pepsin.,Pepsin helps activate more pepsinogen, starting a chain reaction.,Pepsin begins the chemical digestion of proteins.,0,What prevents the gastric juices from digesting the walls of the stomach?,The secretion of pepsin in the inactive form of pepsinogen helps protect the cells of the gastric glands.,Mucus helps protect the stomach lining against HCl and pepsin.,New cells lining (,內層,) the stomach are produced about every three days to those that have been damaged.,21.8 The stomach stores food and breaks it down with acid and enzymes,Esophagus,Sphincter,Lumen (cavity)of stomach,Sphincter,Stomach,Smallintestine,Gastrin,Interiorsurfaceof thestomach,Release of gastric juice(mucus, HCl, and pepsinogen),Pits,Epithelium,Mucouscells,Chief cells,Parietal cells,1,2,3,Gastricgland,Pepsinogen,Pepsin(activeenzyme),HCl,Cl,H,胃泌素,主細胞,胃壁細胞,坑,0,21.9 CONNECTION: Digestive ailments include acid reflux and gastric ulcers,Acid reflux of chyme(,食糜,) in the stomach back into the esophagus causes the feeling of heartburn.,G,astro,e,sophageal,r,eflux,d,isease (GERD) (,胃食道逆流,) results from frequent and severe acid reflux that harms the lining of the esophagus.,Open sores in the lining of the stomach, called ulcers, may form.,Bacterial infections (,Helicobacter pylori,)(,胃幽門螺旋桿菌,) in the stomach and duodenum (,十二指腸,),can produce ulcers.,Bacteria,Mucouslayer ofstomach,0,21.10 The small intestine is the major organ of chemical digestion and nutrient absorption,The small intestine is,named for its smaller diameter,about 6 meters long,the site of much chemical digestion, and,where most nutrients are absorbed.,0,21.10 The small intestine is the major organ of chemical digestion and nutrient absorption,The first 25 cm of the small intestine is the,duodenum (,十二指腸,), where chyme squirted (,噴出,),from the stomach mixes with digestive juices from the pancreas, liver, gallbladder, and gland cells in the intestinal wall.,The,pancreas(,胰臟,),produces pancreatic juice containing a mixture of digestive enzymes and an alkaline (,鹼性,)solution rich in bicarbonate (,碳酸氫根,).,The,liver,produces bile, which is stored in the,gallbladder,until it is needed. Bile breaks up fats into small droplets that are more susceptible to attack by digestive enzymes.,The intestinal wall produces digestive enzymes.,Liver,Gall-bladder,Bile,Intestinalenzymes,Duodenum ofsmall intestine,Chyme,Stomach,Pancreas,Pancreatic juice,麥芽糖,澱粉酶,Trypsin:,胰蛋白酵素,Chymotrypsin:,胰凝乳蛋白酶,0,The surface area for absorption in the small intestine is greatly increased by,folds of the intestinal lining,fingerlike projections called,villi(,絨毛,), and,tiny projections of the surface of intestinal cells called,microvilli(,微絨毛,),.,21.10 The small intestine is the major organ of chemical digestion and nutrient absorption,Vein carryingblood to the liver,Musclelayers,Largecircular folds,Villi,Intestinal wall,Lumen,Nutrientabsorption,Villi,Lymphvessel,Bloodcapillaries,Epithelialcells,Lumen of intestine,Microvilli,Nutrient absorption,Fats,Blood,Lymph,Epithelial cells ofa villus,Aminoacidsandsugars,Fattyacidsandglycerol,0,Nutrients pass into epithelial cells by,diffusion and,against concentration gradients.,Fatty acids and glycerol are,recombined into fats,coated with proteins, and,transported into lymph vessels.,21.10 The small intestine is the major organ of chemical digestion and nutrient absorption,0,Other absorbed nutrients such as amino acids and sugars pass,out of the intestinal epithelium,across the thin walls of the capillaries into blood, and finally,to the liver.,21.10 The small intestine is the major organ of chemical digestion and nutrient absorption,Villi,Lymphvessel,Bloodcapillaries,Epithelialcells,Lumen of intestine,Microvilli,Nutrient absorption,Fats,Blood,Lymph,Epithelial cells ofa villus,Aminoacidsandsugars,Fattyacidsandglycerol,0,21.11 One of the livers many functions is processing nutrient-laden blood from the intestines,Blood from the digestive tract drains,into the,hepatic portal vein(,肝門靜脈,),to the liver.,0,21.11 One of the livers many functions is processing nutrient-laden blood from the intestines,The liver performs many functions. The liver,converts glucose in blood to glycogen (,肝醣,),stores glycogen and releases sugars back into the blood as needed,synthesizes many proteins including blood-clotting proteins and lipoproteins that transport fats and cholesterol to body cells,modifies substances absorbed in the digestive tract into less toxic forms, and,produces bile.,Liver,Intestines,Heart,Hepaticportalvein,0,21.12 The large intestine reclaims water and compacts the feces,The,large intestine, or,colon,is about 1.5 m long and 5 cm in diameter,has a pouch called the,cecum(,盲腸,),near its junction with the small intestine, which bears a small fingerlike extension, the,appendix (,闌尾,),contains large populations of,E. coli, which produce important vitamins,absorbs these vitamins and water into the bloodstream, and,helps form firm feces, which are stored in the,rectum(,直腸,),until elimination.,0,21.12 The large intestine reclaims water and compacts the feces,Diarrhea(,腹瀉,) occurs when too little water is reclaimed from the contents of the large intestine.,Constipation(,便秘,) occurs when too much water is reclaimed.,Cecum,Appendix,End ofsmallintestine,Largeintestine(colon),Unabsorbedfood material,Smallintestine,Rectum,Anus,0,21.13 EVOLUTION CONNECTION: Evolutionary adaptations of vertebrate digestive systems relate to diet,The length of the digestive tract often correlates with diet. In general, the alimentary canals relative to their body size are,longer in herbivores and omnivores and,shorter in carnivores.,Stomach,Small intestine,Cecum,Colon(largeintestine),Carnivore,Herbivore,0,Many herbivores have specializations of the gut that promote the growth of cellulose-digesting bacteria and protists (,原生生物,),because these animals lack the enzymes needed to digest cellulose in plants.,These mutualistic organisms may be housed in,the cecum, in a coyote or koala,the large intestine and the cecum in rabbits and some rodents, or,the stomach of,ruminants (,反芻動物,),such as cattle, sheep, and deer.,21.13 EVOLUTION CONNECTION: Evolutionary adaptations of vertebrate digestive systems relate to diet,0,NUTRITION,0,21.14 Overview: An animals diet must satisfy three needs,All animals have the same basic nutritional needs. Animals must obtain,fuel to power all body activities,organic molecules to build the animals own molecules, and,essential nutrients, or substances the animal cannot make for itself.,0,21.15 Chemical energy powers the body,Cellular respiration produces the bodys energy currency, ATP,by oxidizing organic molecules digested from food and,usually using carbohydrates or fats as fuel.,A gram of fat has more than twice as many calories as a gram of carbohydrate or protein.,0,21.15 Chemical energy powers the body,The energy content of food is measured in,kilocalories,(1,kcal,= 1,000 calories).,Dietary calories are actually kilocalories and are written as Calories.,0,The rate of energy consumption by an animal is called its,metabolic rate(,代謝率,), the sum of all the energy-requiring biochemical reactions over a given interval of time.,The,basal metabolic rate,(,BMR)(,基礎代謝率,),is the energy a resting animal requires,each day,.,The metabolic rate is the BMR plus the energy needed for physical activity.,Excess energy is stored as glycogen or fat.,21.15 Chemical energy powers the body,慢跑,0,21.16 An animals diet must supply essential nutrients,Essential nutrients,cannot be made from any raw material.,There are four classes of essential nutrients.,Essential fatty acids, such as linoleic acid (,亞油酸,), are,used to make phospholipids (,磷脂質,) of cell membranes and,found in seeds, grains, and vegetables.,Essential amino acids,are,used to make proteins and,found in meats, eggs, and milk.,0,Vitamins,are organic nutrients.,Minerals,are simple inorganic nutrients.,Malnutrition(,營養不良,),is a chronic deficiency in calories or one or more essential nutrients. The most common type of human malnutrition is protein deficiency. Under-nutrition(,營養不足,) occurs when,diets do not supply sufficient chemical energy or,a person suffers from anorexia nervosa (,厭食症,) or bulemia (,暴食症,),.,21.16 An animals diet must supply essential nutrients,Essential amino acids,Corn,Beansand other legumes,Lysine,Tryptophan,Isoleucine,Leucine,Phenylalanine,Threonine,(Histidine),Valine,Methionine,0,21.17 A healthy human diet includes 13 vitamins and many essential minerals,Essential vitamins and minerals are,required in minute amounts (,微量,) and,absolutely essential to good health.,Vitamins,are organic nutrients that may be,water soluble, such as vitamins B and C, or,fat soluble, such as vitamins A, D, E, and K.,0,Minerals(,礦物質,),are simple inorganic nutrients.,Calcium and phosphorus are required in larger amounts.,Iron is needed to make hemoglobin (,血紅素,).,Iodine is required to make thyroid hormones.,Most people ingest more salt than they need.,21.17 A healthy human diet includes 13 vitamins and many essential minerals,0,The,Recommended Dietary Allowances (RDAs)(,營養攝取建議表,),are,the minimum amounts of nutrients that are needed each day and,determined by a national scientific panel.,Overdoses of vitamins can be harmful.,In general, excess water-soluble vitamins will be eliminated in urine.,However, excess fat-soluble vitamins can accumulate to toxic levels in body fat.,21.17 A healthy human diet includes 13 vitamins and many essential minerals,0,21.18 SCIENTIFIC DISCOVERY: Scientists use observations and experiments to determine nutritional needs,Many insights into human nutrition have come from epidemiology(,流行病學,), the study of human health and diseases within populations.,The essential need for vitamin C was revealed by the high incidence of scurvy (,壞血病,) in sailors on long sea voyages.,The need for folic acid(,葉酸,) to prevent neural tube defects in newborns was revealed by studies of pregnant women of low socioeconomic status. Since 1998, folic acid has been added to foods such as bread and cereals sold in the United States.,0,21.19 CONNECTION: Food labels provide nutritional information,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.,Ingredients: whole wheatflour, water, high fructose cornsyrup, wheat gluten, soybeanor canola oil, molasses, yeast,salt, cultured whey, vinegar,soy flour, calcium sulfate(source of calcium).,0,21.20 EVOLUTION CONNECTION: The human health problem of obesity may reflect our evolutionary past,Overnourishment is the consumption of more food energy than is needed for normal metabolism.,Obesity,is the excessive accumulation of fat.,The World Health Organization recognizes obesity as a major global health problem.,In the United States, the percentage of obese people has doubled to more than 30% in the past two decades, and another 35% are overweight.,0,Weight problems often begin at a young age.,15% of children and adolescents (,青少年,) in the United States are obese.,Another 17% are overweight.,Obesity leads to,type 2 diabetes,cancer of the colon and breasts, and,cardiovascular disease.,21.20 EVOLUTION CONNECTION: The human health problem of obesity may reflect our evolutionary past,0,Obesity is estimated to be a factor in 300,000 deaths per year in the United States.,A 15-year study published in 2010 indicates that obesity now surpasses smoking in its contribution to disease and the shortening of healthy life spans.,21.20 EVOLUTION CONNECTION: The human health problem of obesity may reflect our evolutionary past,0,The complexity of weight control in humans is evident from studies of the hormone leptin.,Leptin(,瘦素,),is produced by adipose (fat) cells and,suppresses appetite.,Obese children who have an inherited mutant form of the leptin gene lose weight after leptin treatments.,Ho