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1、Important Concepts about Carbohydrates(CHO)有关碳水化合物的重要概念,CHO are made by plants and are the primary source of energy in animal diets碳水化合物主要来源于植物，是动物饲粮的主要能量来源CHO in the cell wall of plants are called fiber,and are less digestible than CHO inside the cell植物细胞壁中的碳水化合物称为纤维，比细胞内的碳水化合物消化性差,Important Concep
2、ts about Carbohydrates(CHO),There are 13 monosaccharides that are physiologically important but none are dietary essential有13种生理学上很重要的单糖，但都不是饲料必需的Ruminants and horses need minimum levels of fiber in the diet for health.反刍动物和马保持健康，饲粮必须提供最低限量的纤维,CARBOHYDRATES碳水化合物,Monosaccharides 单糖Monosaccharides are
3、 the simplest carbohydrates(simple sugars)单糖是最简单的碳水化合物All other carbohydrates are made up of 2 or more monosaccharides.所有其它的碳水化合物都是由两个或两个以上的单糖组成Hydrated carbons;for each C atom there is one water一个碳原子有一分子水CX H2XOX X=number of carbonsExample:glucose:C6 H12 O6,CARBOHYDRATES碳水化合物,Monosaccharides单糖are:p
4、olyhydroxy aldehydes and ketones多羟醛多羟酮Those that are aldehydes are called aldoses有多羟醛的单糖称为醛糖Those that are ketones are called ketoses多羟醛的单糖称为酮糖,醛糖,酮糖,甘油醛,核糖,葡萄糖,半乳糖,二羟基丙酮,核酮糖,果糖,CARBOHYDRATES碳水化合物,A monosaccharide with the letters ul in its name is a ketose;单糖名称中有字母“ul”是酮糖However,not all ketoses hav
5、e ul in their name但并不是所有酮糖在名称中都有字母“ul”Example:Aldose醛糖Ketose酮糖ribose核糖 ribulose核酮糖xylose木糖xylulose木酮糖,CARBOHYDRATES碳水化合物,Monosaccharides单糖Vary in the number of carbon atoms(chain length)碳原子数的变化（链长）3 C=triose三糖4 C=tetrose四糖5 C=pentose五糖 6 C=hexose六糖 7 C=heptose庚糖Therefore,it is possible to have aldot
6、riose丙醛糖,ketotriose酮丙糖,aldohexose己醛糖,ketohexose己酮糖,etc.,醛糖,酮糖,甘油醛,核糖,葡萄糖,半乳糖,二羟基丙酮,核酮糖,果糖,Monosaccharides Exhibit Various Forms of Isomerism,Stereoisomers 立体异构体compounds with same structural formula but different spatial configurations具体相同结构式的化合物，由于不同的立体结构due to presence of asymmetrical C atoms(any
7、C atom attached to four different atoms or groups)导致非对称的碳原子存在number of isomers同分异构体is 2n when n=no.of asymmetrical carbons非对称碳原子数量,D and L Isomerism异构现象,D and L isomers are mirror images of each other.They rotate polarized light to the left(L)or the right(D)D和L异构体是镜像的。Designation of D and L based on
8、 spatial relationship to parent compound glyceraldehyde甘油醛.For monosaccharides with two or more asymmetric carbons,the prefixes D and L refer to the configuration for the asymmetric carbon furtherest from the carbonyl carbon.由于单糖含有两个或两个以上的不对称碳原子，DL是指最远羰基上的不对称碳原子结构。,甘油醛,葡萄糖,D and L Isomerism异构现像,Most
9、 monosaccharides in nature are in the D form,and enzymes responsible for metabolism of monosaccharides are specific for the D form.自然中绝大多数的单糖是D型，酶只对D型有作用效果。This means that animals can utilize the D isomers,but not the L isomers.动物只能利用D型异构体，不能利用L型。,D-Isomers of the aldoses醛糖的D型异构体,Physiological or nu
10、tritional importance,赤藓糖,甘油醛,阿苏糖,核糖,树胶醛糖,木糖,来苏糖,阿洛糖,阿卓糖,葡萄糖,甘露糖,古洛糖,艾杜糖,半乳糖,糖,D-Isomers of the ketoses酮糖D型异构体,二羟基丙酮,赤藓酮糖,核酮糖,木酮糖,阿洛酮糖,果糖,山梨糖,塔格糖,Pyranose and Furanose Rings六环糖和五环糖,The most stable form of aldohexoses is a 6-member ring similar to a pyran.最稳定的己醛糖是与吡喃相似的六环结构For an aldose,the ring struc
11、ture is a hemiacetal(combination of a aldehyde and alcohol group.)醛糖的环结构是半缩醛Due to isomerism on C1(the carbonyl or anomeric carbon atom),this leads to two forms of the D isomer,the and-form.由于异构体在第一个碳原子上，导致D型异构体有和 两种形式For D-glucose,these are-D-glucopyranose and-D glucopyranose吡喃葡萄糖,Alpha and Beta An
12、omers of Glucose 葡萄糖的 和反构体,果糖,核糖,葡萄糖,-吡喃葡萄糖,-吡喃葡萄糖,呋喃核糖,呋喃果糖,Alpha and Beta Glucose Linked by 1-4 Bonds1-4 糖苷键连接的 和葡萄糖,淀粉,纤维素,Pyranose and Furanose rings六环糖和五环糖,For ketohexoses,a 5-member ring,similar to a furan,is found.存在五环的己酮糖，相似呋喃For fructose,the most common form is-D-fructofuranose.呋喃果糖,Monosac
13、charides of Nutritional Importance单糖营养重要作用,Monosaccharides of Nutritional Importance单糖营养重要作用,How many are ketoses,123456,How many are pentoses?,123456,How many are ketoses,123456,How many are pentoses?,123456,Disaccharides-Two monosaccharides linked by glycosidic bond二糖,Maltose 麦芽糖(2 glucose;1-4 bon
14、d)Not found in nature;results from the digestion or chemical breakdown of starch.自然界不存在，由淀粉消化而得Maltose is the basic unit of starch and glycogen.麦芽糖是淀粉和糖原的基本单位,Disaccharides二糖,Sucrose(glucose and fructose)蔗糖Occurs in the free form in most plants;gives fruits their sweet taste在多数植物存在Sugar cane and sug
15、ar beets are processed to produce the table sugar we consume.甘蔗和甜菜生产食用的糖Sucrase is the digestive enzyme needed to digest sucrose into glucose and fructose蔗糖酶Humans and pigs synthesize sucrase;人和猪可合成Ruminants do not.反刍动物不能合成蔗糖酶,Disaccharides,Lactose(glucose and galactose)乳糖Primary carbohydrate in mil
16、k;found in milk;commonly called milk sugar乳糖Lactase 乳糖酶 is the enzyme needed to digest lactoseEasily and completely digested by young animalsLactose intolerance in humans is due to low levels or absence of lactase.乳糖不耐受性是由于体内乳糖酶不足或缺乏引起的,Uses and Sources of Lactose,Oligosaccharides寡糖,Carbohydrates ty
17、pically 2 to 12 monosaccharides long2-12个单糖（2-10）Raffinose(galactose+glucose+fructose)棉子糖Stachyose(galactose+galactose+glucose+水苏糖fructose)Indigestible by mammals,but highly fermentable by microflora of digestive system哺乳动物可以消化High content in soybeans and cottonseed大豆和棉籽中含量高,Which statement is FALSE
18、?,Sucrose is the sweetest of the disaccharidesLactose is the only disaccharide containing glucoseMaltose is not fed to farm animalsMost of the disaccharides are made by plants,Polysaccharides多糖,Starch淀粉,1.Synthesized by plants and used to store energy in seeds and tubers.块茎2.Starch is deposited in g
19、ranules 颗粒inside the cells of tubers and seeds,Starch,3.Starch types:a.Amylose直链淀粉(10 to 30%of starch)(1.)Linear helical chain of glucose linked by 1-4 linkage线性螺旋(2.)Molecular weight 10,000-500,000(3.)Soluble in water,Starch,b.Amylopectin支链淀粉(70 to 90%of starch)(1.)Branched chains of glucose linked
20、 by 1-4 and 1-6 bonds(2.)Branches occur every 12 to 30 glucose molecules(3.)Molecular weight:up to 100 million(4.)Largest molecule in nature,Cereal grains are primarily starch,Cross Section of a Sorghum Kernel高粱横切面,Endosperm 胚乳(Location of Starch),Germ胚芽,Pericarp果皮,Endosperm胚乳,Endosperm,Starch Granu
21、le淀粉颗粒 and Protein Matrix蛋白基质,Granule,Matrix,Protein Matrix(Starch digested away),Starch,Almost completely digested by animals and fermented by bacteria.,Glycogen,1.Branched chains of glucose linked by a 1-4 and 1-6 bonds2.Branches occur every 8 to 12 glucose molecules3.Molecular weight is 50,000-20
22、0,0004.Sometimes called“animal starch”because it is similar in structure to amylopectin支链淀粉,Glycogen,线粒体,Glycogen,5.Found in liver and muscle6.Not stored in large quantities in the body7.During fasting or exercise,glycogen is broken down to glucose which is used as an immediate source of energy.,Fib
23、er is Found in Plant Cell Walls,Cellulose,1.Most abundant substance in plant kingdom2.Structural component of cell walls3.Long straight chains of glucose linked by 1-4 bonds4.Not digested by mammals because animals do not have cellulose enzymes;digested by bacteria in the gastrointestinal tract5.Cot
24、ton is almost pure cellulose.,Cellulose Microfibrils in Apple Skin苹果皮中素微纤维,1 X 1 Micron微米,Hemicellulose半纤维素,Heterogeneous group of polysaccharides异质多糖 associated with cellulose and lignin in cell wall,Hemicellulose,2.Compositiona.Short chain polysaccharides consisting of a backbone chain of xylose,m
25、annoseand galactose with side branching chains of arabinose,glucuronic acid and galactose.甘露糖葡、萄糖醛酸b.Direct bonding of hemicellulose sugars to ligninc.Intermixed with cellulose fibers,Hemicellulose,Not well digested by animals;more fermentable than cellulose by bacteria,Pectins果胶,High molecular weig
26、ht colloidal carbohydrates found in the cell wallOften called intracellular cement细胞内接合剂;found mainly in middle lamella of cell walls细胞壁中胚层Composition-Chains of galacturonic acid with associated arabans(chains of arabinose)and galactans(chains of galactose)Water soluble,forms gelsNot digested by mam
27、mals;fermented by bacteria,Pectin,LIGNIN,1.Not a true carbohydrate;it is a polymer of phenylpropane molecules2.Chemically linked with cellulose and hemicellulose3.Provides rigidity to cell wall4.High content in woody parts of plants,Lignin Stained Red in Wood,LIGNIN,5.Increases with plant maturity6.
28、Indigestible by animals and bacteria,Why Fiber Content of Animal Feeds Is Important,Fiber analyses is one means of estimating the nutritional value of feedstuffs.As fiber content increases,nutritional value decreassFiber is found only in plants,primarily in the cell walls.,Plant Cell Walls,Plant cel
29、l walls,Crude Fiber,Sample,Boiled 30 min.in 1.25%H2SO4,Filtered,Residue,Solubles,Boiled 30 min.in 1.25%NaOH,Residue,Solubles,Filtered,Burned,Crude Fiber,Ash,DriedFat removed byExtracted with ether,Crude Fiber,Assumes material not soluble in weak acid and base are“fiber”.Oldest system still in use;or
30、iginally developed in mid 1800s.Crude fiber does a poor job of quantifying the fiber content of feeds,hemicelluloses are not measured.It is still used to guarantee maximum fiber content in commercial animal feeds.,Van Soest Method,Sample,Heated in a neutral detergent solution(pH 7.0)for 1 hour,Filte
31、red,Neutral Detergent Fiber(NDF)(cell walls-cellulose,hemicellulose,legnin+ash),Cell contents and pectin(protein,lipids,and soluble CHO),Heated in acid detergent solution,(1N H2 SO4)for 1 hour,Filtered,Hemicellulose,Acid Detergent Fiber(ADF)(cellulose,lignin,ash),72%H2 SO4,Cellulose,Lignin+ash,Ligni
32、n,Ash,Burn,Van Soest Method,Separates cell walls(total fiber)from cell contents then separates out the parts of fiberMost common method of determining fiber in animal feedsNDF is the best indicator of total fiber content in animal feedsADF is commonly used as a predictor for digestibility(energy con
33、tent)of forages,because it contains the two least digestible fractions of fiber,Dietary Fiber,Sample,Ether extraction,Lipids,Residue,Heat stable amylase,Protease,Amyloglucosidase,These enzymes mimic digestion in the stomach and small intestine of humans.,Ethanol to precipitate soluble fiber,Soluble
34、sugars and proteins,Filter,Residue,Burn part of residue to determine ash,Part of residue is analyzed to determine insoluble protein,Dietary fiber is determined by substracting ash and protein content from the residue,Dietary Fiber,Uses enzymatic digestion to mimic digestion in humansDietary fiber ca
35、n be subdivided into two categories.,Dietary Fiber,Insoluble fiber procedure identical to the one above except ethanol is not added to precipitate the fibers solubilized by enzymatic digestion.Soluble fiber=Total fiber insoluble fiber.High intakes of soluble fiber by humans is associated with lower
36、incidence of heart diseaseHigh intakes of insoluble fiber by humans is associated with lower incidence of colon cancer.,Comparison of Methods,Which of the bermudagrass hays was most mature at harvest?,Hay 1 has 46%ADFHay 1 has 38%ADFHay 1 has 28%ADF,Which of the bermudagrass hays would most likely b
37、e the most fermentable?,Hay 1 has 46%ADFHay 1 has 38%ADFHay 1 has 28%ADF,Importance of Carbohydratesin Animal and Human Nutrition,Carbohydrates are the primary source of dietary energy for farm animals and humans.Farm animals are fed primarily plants;seeds that contain starch,or forages that contain
38、 fiber.There are no dietary essential monosaccharides.That is,given the proper precursors,the body can synthesize all of the needed monosaccharides.Glucose is the primary carbohydrate catabolized by cells to produce energy.Nerve tissue and red blood cells use only glucose for energy under non-starva
39、tion conditions.,Importance of Carbohydratesin Animal and Human Nutrition,As fiber content of a feed or food increases the amount of usable energy in the product decreases.As forages mature,the cell walls contain more fiber and because less digestible i.e.immature forages have a higher feeding value
40、 than more mature forages.,Late Vegetative,Mid bloom,Mature,Seeded,Effect of NDF Content in Alfalfa Hay on Metabolizable Energy Content for Beef Cattle(NRC,1996),Importance of Carbohydratesin Animal and Human Nutrition,Ruminants and horses need minimum amounts of forage(fiber)in the diet to maintain
41、 normal health and function of the gastrointestinal tract.Inadequate intake of“high”fiber foods(fruits and vegetables)by humans is associated with increased incidence of heart disease and colon cancer.Normal recommendation for adults is 20-35 g of dietary fiber/day.,Which has the most dietary fiber/edible serving?,A,B,C,D,Which has the most dietary fiber?,3 g,9%DM,2 g,11%DM,3 g,18%DM,2 g,19%DM,
