營(yíng)養(yǎng)和消化 大學(xué)生物 Nutrition and Digestion

1、 2012 Pearson Education, Inc.Lecture by Edward J. ZaliskoPowerPoint Lectures forCampbell Biology: Concepts & Connections, Seventh EditionReece, Taylor, Simon, and DickeyNutrition and DigestionIntroduction All animals must eat to provide energy and the building blocks used to assemble (組合) new molecu

2、les. Animals also need essential vitamins and minerals.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

3、 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 IdeasNutritionObtaining andProcessing FoodThe HumanDigestive SystemOBTAINING AND PROCESSING FOOD21.1 A

4、nimals obtain and ingest their food in a variety of ways Most animals have one of three kinds of diets. Herbivores (草食草食) eat plants and include cattle(家牛), snails, and sea urchins (海膽). Carnivores (肉食肉食) eat meat and include lions, hawks, and spiders. Omnivores (雜食雜食) eat plants and other animals a

5、nd include humans, roaches(蟑螂), raccoons(浣熊), and crows (烏鴉). Animals obtain and ingest their food in different ways. Suspension feeders (懸浮物攝食者懸浮物攝食者) sift (過濾) small organisms or food particles from water. Substrate feeders (基質(zhì)攝食者基質(zhì)攝食者) live in or on their food source and eat their way through it.

6、 Fluid feeders (流體攝食者流體攝食者) suck nutrient-rich fluids from a living host. Bulk feeders (大塊攝食者大塊攝食者) ingest large pieces of food.21.1 Animals obtain and ingest their food in a variety of ways管蠕蟲CaterpillarFeces蒼鷺21.2 Overview: Food processing occurs in four stages Food is processed in four stages.1.

7、Ingestion (攝食攝食) is the act of eating.2. Digestion (消化消化) is the breaking down of food into molecules small enough for the body to absorb.3. Absorption (吸收吸收) is the take-up of the products of digestion, usually by the cells lining (內(nèi)襯) the digestive tract.4. Elimination (排除排除) is the removal of und

8、igested materials out of the digestive tract.MechanicaldigestionPiecesof foodSmallmoleculesChemicaldigestion(hydrolysis)Nutrientmoleculesenter bodycellsUndigestedmaterialIngestionDigestionAbsorptionElimination3421Food MoleculesComponentsProteinProtein-digestingenzymesCarbohydrate-digestingenzymesNuc

9、leic-acid-digestingenzymesFat-digestingenzymesAmino acidsPolysaccharideDisaccharideMonosaccharidesNucleic acidNucleotidesFatGlycerol Fatty acids(核苷酸)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

10、腸動(dòng)物)and flatworms(扁蟲) have a gastrovascular cavity(消化循環(huán)腔消化循環(huán)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. Most animals have an alimentary canal (消消化

11、道化道) with a mouth, an anus, and specialized regions associated with one-way flow of food.21.3 Digestion occurs in specialized compartments The normal one-way flow moves food into the pharynx (咽咽) or throat, down the esophagus (食道食道) to a crop (嗉囊嗉囊) where food is softened and stored, gizzard (砂囊砂囊),

12、 where food is ground (磨碎) and stored, and/or stomach (胃胃) 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(肛門肛門).21.3 Digestion occurs in specialized compartmentsTentacles3124Mo

13、uthFood(a water flea)GastrovascularcavityDigestive enzymesbeing released froma gland cellFood digested tosmall particlesA food particlebeing engulfedA food particledigested in afood vacuolehydra(水螅)(吞入)EarthwormMouthPharynxEsophagusCropGizzardIntestineAnusGrasshopperEsophagusEsophagusBirdMouthMouthC

14、ropCropGizzardStomachIntestineAnusAnusMidgutHindgutGastricpouches嗉嗉囊砂囊後腸中腸胃囊咽THE HUMAN DIGESTIVE SYSTEM21.4 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

15、 along by alternating waves of contraction and relaxation by smooth muscle in the walls of the canal in a process called peristalsis (蠕動(dòng)蠕動(dòng)), and moved in and out of the stomach by sphincters (括約肌括約肌).21.4 The human digestive system consists of an alimentary canal and accessory glands The final steps

16、 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.KeyAlimentary canalAccessory digestiveglandsRectumAnusSmallintestineLargeintestineStomachEsophagusOr

17、alcavityA schematic diagram of thehuman digestive systemSalivaryglandsGall-bladderLiverPancreas膽囊EsophagusPharynxEsophagusSphinctersStomachSmall intestineNasal cavityOral cavity(mouth)TongueSmallintestineLargeintestineRectumAnusSalivaryglandsGall-bladderLiverPancreas21.5 Digestion begins in the oral

18、 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(tuán)食團(tuán)), and moves it toward the pharynx.21.5 Digestion begins in the oral cavity Salivary glands (

19、唾液腺唾液腺) release a slippery glycoprotein(糖蛋白) that moistens (濡濕) and lubricates (潤(rùn)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.IncisorsCaninePre

20、molarsMolars“Wisdom”toothTongueSalivaryglandsOpening ofa salivarygland duct門牙犬齒前臼齒臼齒智齒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.21.6 After

21、 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 rela

22、xed)Epiglottis downLarynx up會(huì)厭Swallowing completed(sphincter contracted)Epiglottis upLarynx downEsophageal sphincter(contracted)Bolus offoodMuscles contract,squeezing the bolusthrough the esophagus.Muscles relax,allowing thepassagewayto open.Bolus offoodStomach21.7 CONNECTION: The Heimlich maneuver

23、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(dòng)) food from the pharynx or trachea during choking (窒息). Brain damage will occur within minutes if no airway is open.21.8 The stomach stores food and br

24、eaks 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(胃液胃液), made up of Mucus (粘液) a protein-digesting enzyme, and strong acid with a pH of about 2 that kills ingested b

25、acteria, breaks apart cells in food, and denatures proteins.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(nèi)腔) of the stomach. HCl converts some pepsinogen to pepsin. Pep

26、sin helps activate more pepsinogen, starting a chain reaction. Pepsin begins the chemical digestion of proteins. 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 h

27、elps protect the stomach lining against HCl and pepsin. New cells lining (內(nèi)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 enzymesEsophagusSphincterLumen (cavity)of stomachSphincterStomachSmallintestineG

28、astrinInteriorsurfaceof thestomachRelease of gastric juice(mucus, HCl, and pepsinogen)PitsEpitheliumMucouscellsChief cellsParietal cells123GastricglandPepsinogenPepsin(activeenzyme)HClCl H 胃泌素主細(xì)胞胃壁細(xì)胞坑21.9 CONNECTION: Digestive ailments include acid reflux and gastric ulcers Acid reflux of chyme(食糜)

29、in the stomach back into the esophagus causes the feeling of heartburn. Gastroesophageal reflux disease (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 (Helicoba

30、cter pylori)(胃幽門螺旋桿菌) in the stomach and duodenum (十二指腸) can produce ulcers.BacteriaMucouslayer ofstomach21.10 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 di

31、gestion, and where most nutrients are absorbed.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 (十二指腸十二指腸), where chyme squirted (噴出) from the stomach mixes with digestive juices from the pancreas, liver

32、, gallbladder, and gland cells in the intestinal wall. The pancreas(胰臟胰臟) 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 i

33、nto small droplets that are more susceptible to attack by digestive enzymes. The intestinal wall produces digestive enzymes.LiverGall-bladderBileIntestinalenzymesDuodenum ofsmall intestineChymeStomachPancreasPancreatic juice麥芽糖澱粉酶Trypsin: 胰蛋白酵素Chymotrypsin:胰凝乳蛋白酶 The surface area for absorption in t

34、he small intestine is greatly increased by folds of the intestinal lining, fingerlike projections called villi(絨毛絨毛), and tiny projections of the surface of intestinal cells called microvilli(微絨毛微絨毛).21.10 The small intestine is the major organ of chemical digestion and nutrient absorptionVein carry

35、ingblood to the liverMusclelayersLargecircular foldsVilliIntestinal wallLumenNutrientabsorptionVilliLymphvesselBloodcapillariesEpithelialcellsLumen of intestineMicrovilliNutrient absorptionFatsBloodLymphEpithelial cells ofa villusAminoacidsandsugarsFattyacidsandglycerol Nutrients pass into epithelia

36、l 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 Other absorbed nutrients such as amino acid

37、s 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 absorptionVilliLymphvesselBloodcapillariesEpithelialcellsLumen of intestineMicrovilliNutri

38、ent absorptionFatsBloodLymphEpithelial cells ofa villusAminoacidsandsugarsFattyacidsandglycerol21.11 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(肝門靜脈肝門靜脈) to the liver.21.11 One of the live

39、rs 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 lipopro

40、teins that transport fats and cholesterol to body cells, modifies substances absorbed in the digestive tract into less toxic forms, and produces bile. LiverIntestinesHeartHepaticportalvein21.12 The large intestine reclaims water and compacts the feces The large intestine, or colon, is about 1.5 m lo

41、ng and 5 cm in diameter, has a pouch called the cecum(盲腸盲腸) near its junction with the small intestine, which bears a small fingerlike extension, the appendix (闌尾闌尾), contains large populations of E. coli, which produce important vitamins, absorbs these vitamins and water into the bloodstream, and h

42、elps form firm feces, which are stored in the rectum(直直腸腸) until elimination.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

43、AppendixEnd ofsmallintestineLargeintestine(colon)Unabsorbedfood materialSmallintestineRectumAnus21.13 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

44、 to their body size are longer in herbivores and omnivores and shorter in carnivores.StomachSmall intestineCecumColon(largeintestine)CarnivoreHerbivore Many herbivores have specializations of the gut that promote the growth of cellulose-digesting bacteria and protists (原生生物) because these animals la

45、ck 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(dòng)物反芻動(dòng)物) such as cattle, sheep, and deer.21.13 EVOLUTION CONNECTION: Evoluti

46、onary adaptations of vertebrate digestive systems relate to dietNUTRITION21.14 Overview: An animals diet must satisfy three needs All animals have the same basic nutritional needs. Animals must obtain1. fuel to power all body activities,2. organic molecules to build the animals own molecules, and3.

47、essential nutrients, or substances the animal cannot make for itself.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 twic

48、e as many calories as a gram of carbohydrate or protein.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. The rate of energy consumption by an animal is calle

49、d its metabolic rate(代謝率代謝率), the sum of all the energy-requiring biochemical reactions over a given interval of time. The basal metabolic rate (BMR)(基礎(chǔ)代謝率基礎(chǔ)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 energ

50、y is stored as glycogen or fat.21.15 Chemical energy powers the body慢跑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.1. Essential fatty acids, such as linoleic acid (亞油酸), are used to make

51、phospholipids (磷脂質(zhì)) of cell membranes and found in seeds, grains, and vegetables.2. Essential amino acids are used to make proteins and found in meats, eggs, and milk.3. Vitamins are organic nutrients.4. Minerals are simple inorganic nutrients. Malnutrition(營(yíng)養(yǎng)不良營(yíng)養(yǎng)不良) is a chronic deficiency in calor

52、ies or one or more essential nutrients. The most common type of human malnutrition is protein deficiency. Under-nutrition(營(yíng)養(yǎng)不足) occurs when diets do not supply sufficient chemical energy or a person suffers from anorexia nervosa (厭食癥) or bulemia (暴食癥).21.16 An animals diet must supply essential nutr

53、ientsEssential amino acidsCornBeansand other legumesLysineTryptophanIsoleucineLeucinePhenylalanineThreonine(Histidine)ValineMethionine21.17 A healthy human diet includes 13 vitamins and many essential minerals Essential vitamins and minerals are required in minute amounts (微量) and absolutely essenti

54、al 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. Minerals(礦物質(zhì)礦物質(zhì)) are simple inorganic nutrients. Calcium and phosphorus are required in larger amounts. Iron is needed to make hemoglobin (血紅素). Iod

55、ine 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 The Recommended Dietary Allowances (RDAs)(營(yíng)養(yǎng)攝取建議表營(yíng)養(yǎng)攝取建議表) are the minimum amounts of nutrients that are needed each day and determined by

56、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 minerals21.18 S

57、CIENTIFIC DISCOVERY: Scientists use observations and experiments to determine nutritional needs Many insights into human nutrition have come from epidemiology(流行病學(xué)), the study of human health and diseases within populations. The essential need for vitamin C was revealed by the high incidence of scur

58、vy (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.21.19 CONNECTION:

59、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,

60、 wheat gluten, soybeanor canola oil, molasses, yeast,salt, cultured whey, vinegar,soy flour, calcium sulfate(source of calcium).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