DOCSLIB.ORG

Carbohydrates Adapted from Pellar

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Carbohydrates Adapted from Pellar Carbohydrates Adapted from Pellar OBJECTIVE: To learn about carbohydrates and their reactivities BACKGROUND: Carbohydrates are a major food source, with most dietary guidelines recommending that 45-65% of daily calories come from carbohydrates. Rice, potatoes, bread, pasta and candy are all high in carbohydrates, specifically starches and sugars. These compounds are just a few examples of carbohydrates. Other carbohydrates include fibers such as cellulose and pectins. In addition to serving as the primary source of energy for the body, sugars play a number of other key roles in biological processes, such as forming part of the backbone of DNA structure, affecting cell-to-cell communication, nerve and brain cell function, and some disease pathways. Carbohydrates are defined as polyhydroxy aldehydes or polyhydroxy ketones, or compounds that break down into these substances. They can be categorized according to the number of carbons in the structure and whether a ketone or an aldehyde group is present. Glucose, for example, is an aldohexose because it contains six carbons and an aldehyde functional group. Similarly, fructose would be classified as a ketohexose. glucose fructose A more general classification scheme exists where carbohydrates are broken down into the groups monosaccharides, disaccharides, and polysaccharides. Monosaccharides are often referred to as simple sugars. These compounds cannot be broken down into smaller sugars by acid hydrolysis. Glucose, fructose and ribose are examples of monosaccharides. Monosaccharides exist mostly as cyclic structures containing hemiacetal or hemiketal groups. These structures in solution are in equilibrium with the corresponding open-chain structures bearing aldehyde or ketone functional groups. The chemical linkage of two monosaccharides forms disaccharides. Sucrose, table sugar, is made when a glycosidic bond forms between glucose and fructose. Lactose and maltose are two other examples of disaccharides. Joining many monosaccharide units through glycosidic bonds forms polysaccharides. Starch, commonly called a complex carbohydrate on food labels, and cellulose are examples. Chemical reactivity of carbohydrates Oxidation: Carbohydrates that can undergo oxidation, such as glucose, are known as reducing sugars. All monosaccharides are reducing sugars sine they have either the aldehyde functional group or an alpha-hydroxy ketone group that can undergo oxidation. Many disaccharides are also reducing sugars. Sucrose, however cannot be oxidized as so is not a reducing sugar. Fehling’s reagent will be used to test the ability of carbohydrates to act as reducing sugars. A red precipitate signals a positive reaction. Barfoed’s reagent can also be used for oxidation. It is a much milder oxidizing agent than Fehling’s reagent and can be used to distinguish between monosaccharides and reducing disaccharides. Reducing disaccharides undergo a slow reaction or none at all with Barfoed’s reagent, while monosaccharides react quickly. Again, the presence of a red precipitate indicates a positive reaction. Dehydration: Carbohydrates can undergo dehydration reactions. To differentiate between aldoses and ketoses, Seliwanoff’s reagent will be used. When a ketose reacts with this reagent (resorcinol in 6M HCl), a cherry-red colored complex forms. Aldoses take much longer to react. Disaccharides and polysaccharides eventually hydrolyze to monosaccharides in the acidic environment of this test and will also form a red-colored solution slowly over time. Reaction with iodine: Starch reacts with a solution containing iodine to reveal a deep blue color. This color may vary according to the structure of the polysaccharide (one component of starch, amylose, gives a blue color while the other component, amylopectin, gives a violet color). Simpler carbohydrates will not change the color of the iodine solution. Hydrolysis: Polysaccharides and disaccharides can be broken down in the presence of acid. A carbohydrate such as sucrose that has a single glycosidic linkage bond becomes fully hydrolyzed in an acid solution. Large polysaccharides typically undergo a partial hydrolysis to produce many shortened starch molecules, known as dextrins. Enzymatic tests: Urinalysis for glucose used to rely primarily on the Barfoed’s test, which was non-specific for the type of sugar found in the urine. Modern test strips are more specific enzyme-based assays that react only in the presence of glucose. PROCEDURE: Perform each of the following tests on glucose, fructose, lactose, sucrose, starch and your unknown unless otherwise indicated. Fehling’s test: To each of 6 test tubes, add 6 drops of the substances to be tested. In a large test tube, mix 6 mL of Fehling’s solution A with 6 mL of Fehling’s solution B. Add 2 mL of this mixture to each tube and stir thoroughly. Place the test tubes in a boiling- water bath for 5 minutes and record your observations. The formation of a red precipitate indicates a positive reaction. Barfoed’s test: To each of 6 test tubes, add 1 mL of the solutions to be tested. Then add 3 mL of Barfoed’s reagent to each test tube and mix thoroughly. Place the test tubes in a boiling water bath for 5 minutes and record your observations. The formation of a red precipitate indicates a positive reaction. Seliwanoff’s test: (avoid contact with this solution since it contains hydrochloric acid) To each of 6 test tubes, add 10 drops of the solutions to be tested. A seventh test tube containing 10 drops of distilled water should also be prepared. Add 4 mL of Seliwanoff’s reagent to each test tube and mix. Place the test tubes in a boiling-water bath and note the time needed for any color change to occur. Discontinue heating after 10 minutes. A color change indicates a positive reaction. Record your observations. Iodine test: To each of 6 test tubes, add 1 mL of the solutions to be tested. A seventh test tube containing 1 mL of distilled water should also be prepared. Add 3 drops of iodine solution and record your observations. Hydrolysis: (test only sucrose and starch) To each of two tests tubes, add 5 mL of the solutions to be tested. Add 10 drops of 3 M HCl and mix thoroughly. Heat in a boiling water bath for 20 minutes. Allow the solution to cool and then add 3 M NaOH dropwise until the solution tests neutral on pH paper. Test the hydrolyzed sucrose solution using the Fehling’s test above. Perform the iodine test on the hydrolyzed starch solution. Urinalysis test strips: Each student should test a single solution. Create a table on the blackboard to ensure that all solutions are tested and everyone has all of the results. Place a single drop of the solution to be tested on a chemical test strip. Read the concentration of glucose using the scale on the side of the container. .
Load more

Recommended publications
  • Pentose PO4 Pathway, Fructose, Galactose Metabolism.Pptx
    Pentose PO4 pathway, Fructose, galactose metabolism The Entner Doudoroff pathway begins with hexokinase producing Glucose 6 PO4 , but produce only one ATP. This pathway prevalent in anaerobes such as Pseudomonas, they doe not have a Phosphofructokinase. The pentose phosphate pathway (also called the phosphogluconate pathway and the hexose monophosphate shunt) is a biochemical pathway parallel to glycolysis that generates NADPH and pentoses. While it does involve oxidation of glucose, its primary role is anabolic rather than catabolic. There are two distinct phases in the pathway. The first is the oxidative phase, in which NADPH is generated, and the second is the non-oxidative synthesis of 5-carbon sugars. For most organisms, the pentose phosphate pathway takes place in the cytosol. For each mole of glucose 6 PO4 metabolized to ribulose 5 PO4, 2 moles of NADPH are produced. 6-Phosphogluconate dh is not only an oxidation step but it’s also a decarboxylation reaction. The primary results of the pathway are: The generation of reducing equivalents, in the form of NADPH, used in reductive biosynthesis reactions within cells (e.g. fatty acid synthesis). Production of ribose-5-phosphate (R5P), used in the synthesis of nucleotides and nucleic acids. Production of erythrose-4-phosphate (E4P), used in the synthesis of aromatic amino acids. Transketolase and transaldolase reactions are similar in that they transfer between carbon chains, transketolases 2 carbon units or transaldolases 3 carbon units. Regulation; Glucose-6-phosphate dehydrogenase is the rate- controlling enzyme of this pathway. It is allosterically stimulated by NADP+. The ratio of NADPH:NADP+ is normally about 100:1 in liver cytosol.
    [Show full text]
  • Carbohydrates: Structure and Function
    CARBOHYDRATES: STRUCTURE AND FUNCTION Color index: . Very important . Extra Information. “ STOP SAYING I WISH, START SAYING I WILL” 435 Biochemistry Team *هذا العمل ﻻ يغني عن المصدر المذاكرة الرئيسي • The structure of carbohydrates of physiological significance. • The main role of carbohydrates in providing and storing of energy. • The structure and function of glycosaminoglycans. OBJECTIVES: 435 Biochemistry Team extra information that might help you 1-synovial fluid: - It is a viscous, non-Newtonian fluid found in the cavities of synovial joints. - the principal role of synovial fluid is to reduce friction between the articular cartilage of synovial joints during movement O 2- aldehyde = terminal carbonyl group (RCHO) R H 3- ketone = carbonyl group within (inside) the compound (RCOR’) 435 Biochemistry Team the most abundant organic molecules in nature (CH2O)n Carbohydrates Formula *hydrate of carbon* Function 1-provides important part of energy Diseases caused by disorders of in diet . 2-Acts as the storage form of energy carbohydrate metabolism in the body 3-structural component of cell membrane. 1-Diabetesmellitus. 2-Galactosemia. 3-Glycogen storage disease. 4-Lactoseintolerance. 435 Biochemistry Team Classification of carbohydrates monosaccharides disaccharides oligosaccharides polysaccharides simple sugar Two monosaccharides 3-10 sugar units units more than 10 sugar units Joining of 2 monosaccharides No. of carbon atoms Type of carbonyl by O-glycosidic bond: they contain group they contain - Maltose (α-1, 4)= glucose + glucose -Sucrose (α-1,2)= glucose + fructose - Lactose (β-1,4)= glucose+ galactose Homopolysaccharides Heteropolysaccharides Ketone or aldehyde Homo= same type of sugars Hetero= different types Ketose aldose of sugars branched unBranched -Example: - Contains: - Contains: Examples: aldehyde group glycosaminoglycans ketone group.
    [Show full text]
  • PENTOSE PHOSPHATE PATHWAY — Restricted for Students Enrolled in MCB102, UC Berkeley, Spring 2008 ONLY
    Metabolism Lecture 5 — PENTOSE PHOSPHATE PATHWAY — Restricted for students enrolled in MCB102, UC Berkeley, Spring 2008 ONLY Bryan Krantz: University of California, Berkeley MCB 102, Spring 2008, Metabolism Lecture 5 Reading: Ch. 14 of Principles of Biochemistry, “Glycolysis, Gluconeogenesis, & Pentose Phosphate Pathway.” PENTOSE PHOSPHATE PATHWAY This pathway produces ribose from glucose, and it also generates 2 NADPH. Two Phases: [1] Oxidative Phase & [2] Non-oxidative Phase + + Glucose 6-Phosphate + 2 NADP + H2O Ribose 5-Phosphate + 2 NADPH + CO2 + 2H ● What are pentoses? Why do we need them? ◦ DNA & RNA ◦ Cofactors in enzymes ● Where do we get them? Diet and from glucose (and other sugars) via the Pentose Phosphate Pathway. ● Is the Pentose Phosphate Pathway just about making ribose sugars from glucose? (1) Important for biosynthetic pathways using NADPH, and (2) a high cytosolic reducing potential from NADPH is sometimes required to advert oxidative damage by radicals, e.g., ● - ● O2 and H—O Metabolism Lecture 5 — PENTOSE PHOSPHATE PATHWAY — Restricted for students enrolled in MCB102, UC Berkeley, Spring 2008 ONLY Two Phases of the Pentose Pathway Metabolism Lecture 5 — PENTOSE PHOSPHATE PATHWAY — Restricted for students enrolled in MCB102, UC Berkeley, Spring 2008 ONLY NADPH vs. NADH Metabolism Lecture 5 — PENTOSE PHOSPHATE PATHWAY — Restricted for students enrolled in MCB102, UC Berkeley, Spring 2008 ONLY Oxidative Phase: Glucose-6-P Ribose-5-P Glucose 6-phosphate dehydrogenase. First enzymatic step in oxidative phase, converting NADP+ to NADPH. Glucose 6-phosphate + NADP+ 6-Phosphoglucono-δ-lactone + NADPH + H+ Mechanism. Oxidation reaction of C1 position. Hydride transfer to the NADP+, forming a lactone, which is an intra-molecular ester.
    [Show full text]
  • Nucleosides & Nucleotides
    Nucleosides & Nucleotides Biochemistry Fundamentals > Genetic Information > Genetic Information NUCLEOSIDE AND NUCLEOTIDES SUMMARY NUCLEOSIDES  • Comprise a sugar and a base NUCLEOTIDES  • Phosphorylated nucleosides (at least one phosphorus group) • Link in chains to form polymers called nucleic acids (i.e. DNA and RNA) N-BETA-GLYCOSIDIC BOND  • Links nitrogenous base to sugar in nucleotides and nucleosides • Purines: C1 of sugar bonds with N9 of base • Pyrimidines: C1 of sugar bonds with N1 of base PHOSPHOESTER BOND • Links C3 or C5 hydroxyl group of sugar to phosphate NITROGENOUS BASES  • Adenine • Guanine • Cytosine • Thymine (DNA) 1 / 8 • Uracil (RNA) NUCLEOSIDES • =sugar + base • Adenosine • Guanosine • Cytidine • Thymidine • Uridine NUCLEOTIDE MONOPHOSPHATES – ADD SUFFIX 'SYLATE' • = nucleoside + 1 phosphate group • Adenylate • Guanylate • Cytidylate • Thymidylate • Uridylate Add prefix 'deoxy' when the ribose is a deoxyribose: lacks a hydroxyl group at C2. • Thymine only exists in DNA (deoxy prefix unnecessary for this reason) • Uracil only exists in RNA NUCLEIC ACIDS (DNA AND RNA)  • Phosphodiester bonds: a phosphate group attached to C5 of one sugar bonds with - OH group on C3 of next sugar • Nucleotide monomers of nucleic acids exist as triphosphates • Nucleotide polymers (i.e. nucleic acids) are monophosphates • 5' end is free phosphate group attached to C5 • 3' end is free -OH group attached to C3 2 / 8 FULL-LENGTH TEXT • Here we will learn about learn about nucleoside and nucleotide structure, and how they create the backbones of nucleic acids (DNA and RNA). • Start a table, so we can address key features of nucleosides and nucleotides. • Denote that nucleosides comprise a sugar and a base.
    [Show full text]
  • Part 1 in Our Series of Carbohydrate Lectures. in This Section, You Will Learn About Monosaccharide Structure
    Welcome to Part 1 in our series of Carbohydrate lectures. In this section, you will learn about monosaccharide structure. The building blocks of larger carbohydrate polymers. 1 First, let’s review why learning about carbohydrates is important. Carbohydrates are used by biological systems as fuels and energy resources. Carbohydrates typically provide quick energy and are one of the primary energy storage forms in animals. Carbohydrates also provide the precursors to other major macromolecules within the body, including the deoxyribose and ribose required for nucleic acid biosynthesis. Carbohydrates can also provide structural support and cushioning/shock absorption, as well as cell‐cell communication, identification, and signaling. 2 Carbohydrates, as their name implies, are water hydrates of carbon, and they all have the same basic core formula (CH2O)n and are always found in the ratio of 1 carbon to 2 hydrogens to 1 oxygen (1:2:1) making them easy to identify from their molecular formula. 3 Carbohydrates can be divided into subcategories based on their complexity. The simplest carbohydrates are the monosaccharides which are the simple sugars required for the biosynthesis of all the other carbohydrate types. Disaccharides consist of two monosaccharides that have been joined together by a covalent bond called the glycosidic bond. Oligosaccharides are polymers that consist of a few monosaccharides covalently linked together, and Polysaccharides are large polymers that contain hundreds to thousands of monosaccharide units all joined together by glycosidic bonds. The remainder of this lecture will focus on monosaccharides 4 Monosaccharides all have alcohol functional groups associated with them. In addition they also have one additional functional group, either an aldehyde or a ketone.
    [Show full text]
  • 8| Nucleotides and Nucleic Acids
    8| Nucleotides and Nucleic Acids © 2013 W. H. Freeman and Company CHAPTER 8 Nucleotides and Nucleic Acids Key topics: – Biological function of nucleotides and nucleic acids – Structures of common nucleotides – Structure of double‐stranded DNA – Structures of ribonucleic acids – Denaturation and annealing of DNA – Chemistry of nucleic acids; mutagenesis Functions of Nucleotides and Nucleic Acids • Nucleotide Functions: – Energy for metabolism (ATP) – Enzyme cofactors (NAD+) –Signal transduction (cAMP) • Nucleic Acid Functions: – Storage of genetic info (DNA) – Transmission of genetic info (mRNA) –Processing of genetic information (ribozymes) –Protein synthesis (tRNA and rRNA) Nucleotides and Nucleosides • Nucleotide = – Nitrogeneous base –Pentose – Phosphate • Nucleoside = – Nitrogeneous base –Pentose • Nucleobase = – Nitrogeneous base Phosphate Group •Negatively charged at neutral pH • Typically attached to 5’ position – Nucleic acids are built using 5’‐triphosphates •ATP, GTP, TTP, CTP – Nucleic acids contain one phosphate moiety per nucleotide •May be attached to other positions Other Nucleotides: Monophosphate Group in Different Positions Pentose in Nucleotides • ‐D‐ribofuranose in RNA • ‐2’‐deoxy‐D‐ribofuranose in DNA •Different puckered conformations of the sugar ring are possible Nucleobases •Derivatives of pyrimidine or purine • Nitrogen‐containing heteroaromatic molecules •Planar or almost planar structures •Absorb UV light around 250–270 nm Pyrimidine Bases • Cytosine is found in both DNA and RNA •Thymineis found only in DNA
    [Show full text]
  • Ii- Carbohydrates of Biological Importance
    Carbohydrates of Biological Importance 9 II- CARBOHYDRATES OF BIOLOGICAL IMPORTANCE ILOs: By the end of the course, the student should be able to: 1. Define carbohydrates and list their classification. 2. Recognize the structure and functions of monosaccharides. 3. Identify the various chemical and physical properties that distinguish monosaccharides. 4. List the important monosaccharides and their derivatives and point out their importance. 5. List the important disaccharides, recognize their structure and mention their importance. 6. Define glycosides and mention biologically important examples. 7. State examples of homopolysaccharides and describe their structure and functions. 8. Classify glycosaminoglycans, mention their constituents and their biological importance. 9. Define proteoglycans and point out their functions. 10. Differentiate between glycoproteins and proteoglycans. CONTENTS: I. Chemical Nature of Carbohydrates II. Biomedical importance of Carbohydrates III. Monosaccharides - Classification - Forms of Isomerism of monosaccharides. - Importance of monosaccharides. - Monosaccharides derivatives. IV. Disaccharides - Reducing disaccharides. - Non- Reducing disaccharides V. Oligosaccarides. VI. Polysaccarides - Homopolysaccharides - Heteropolysaccharides - Carbohydrates of Biological Importance 10 CARBOHYDRATES OF BIOLOGICAL IMPORTANCE Chemical Nature of Carbohydrates Carbohydrates are polyhydroxyalcohols with an aldehyde or keto group. They are represented with general formulae Cn(H2O)n and hence called hydrates of carbons.
    [Show full text]
  • Nucleotides and Nucleic Acids
    CHAPTER 8 Nucleotides and Nucleic Acids Functions of Nucleotides and Nucleic Acids • Nucleotide Functions: – Energy for metabolism (ATP) – Enzyme cofactors (NAD+) – Signal transduction (cAMP) • Nucleic Acid Functions: – Storage of genetic info (DNA) – Transmission of genetic info (mRNA) – Processing of genetic information (ribozymes) – Protein synthesis (tRNA and rRNA) Nucleotides and Nucleosides • Nucleotide = – Nitrogeneous base – Pentose – Phosphate • Nucleoside = – Nitrogeneous base – Pentose • Nucleobase = – Nitrogeneous base Phosphate Group • Negatively charged at neutral pH • Typically attached to 5’ position – Nucleic acids are built using 5’- triphosphates • ATP, GTP, TTP, CTP – Nucleic acids contain one phosphate moiety per nucleotide • May be attached to other positions Other Nucleotides: Monophosphate Group in Different Positions Pentose in Nucleotides • -D-ribofuranose in RNA • -2’-deoxy-D-ribofuranose in DNA • Different puckered conformations of the sugar ring are possible Purine Bases • Adenine and guanine are found in both RNA and DNA • Also good H-bond donors and acceptors • Adenine pKa at N1 is 3.8 • Guanine pKa at N7 is 2.4 • Neutral molecules at pH 7 • Derivatives of pyrimidine or purine • Nitrogen-containing heteroaromatic molecules • Planar or almost planar structures • Absorb UV light around 250–270 nm Pyrimidine Bases • Cytosine is found in both DNA and RNA • Thymine is found only in DNA • Uracil is found only in RNA • All are good H-bond donors and acceptors • Cytosine pKa at N3 is 4.5 • Thymine pKa at N3 is 9.5
    [Show full text]
  • Carbohydrates: Disaccharides and Polysaccharides
    Carbohydrates: Disaccharides and Polysaccharides Disaccharides Linkage of the anomeric carbon of one monosaccharide to the OH of another monosaccharide via a condensation reaction. The bond is termed a glycosidic bond. The end of the disaccharide that contains the anomeric carbon is referred to as the reducing end because it is capable of reducing various metal ions. Formation of a glycosidic bond between two glucose molecules. Nomenclature: To describe disaccharides you need to specify the following: 1. The names of the two monosaccharides. 2. How they are linked together (one anomeric is always used). 3. The configuration of the anomeric carbons on both monosaccharides. The Six Simple Rules for Naming Disaccharides are as follows: 1. The non-reducing end defines the first sugar. 2. Configuration of the anomeric carbon of the 1st sugar (α,β). 3. Name of 1st monosaccharide, root name followed by pyranosyl (6- ring) or furanosyl (5-ring). 4. Atoms which are linked together, 1st sugar then 2nd sugar. 5. Configuration of the anomeric carbon of the second sugar (α,β) (often omitted if the anomeric carbon is free since α and β forms are in equilibrium.) 6. Name of 2nd monosaccharide, root name followed by pyranose (6- ring) or furanose (5-ring) (If both anomeric carbons are involved, then the name ends in ‘oside”, not ‘ose’) Example: Sucrose (table sugar): The anomeric carbon of glucose forms a bridge to the anomeric carbon of fructose. Since there is no reducing end, either sugar can be used to begin the name. Sucrose, drawn in two different ways. Note that both anomeric carbons are involved in the glycosidic linkage, thus both conformations have to be specified.
    [Show full text]
  • Structures and Characteristics of Carbohydrates in Diets Fed to Pigs: a Review Diego M
    Navarro et al. Journal of Animal Science and Biotechnology (2019) 10:39 https://doi.org/10.1186/s40104-019-0345-6 REVIEW Open Access Structures and characteristics of carbohydrates in diets fed to pigs: a review Diego M. D. L. Navarro1, Jerubella J. Abelilla1 and Hans H. Stein1,2* Abstract The current paper reviews the content and variation of fiber fractions in feed ingredients commonly used in swine diets. Carbohydrates serve as the main source of energy in diets fed to pigs. Carbohydrates may be classified according to their degree of polymerization: monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Digestible carbohydrates include sugars, digestible starch, and glycogen that may be digested by enzymes secreted in the gastrointestinal tract of the pig. Non-digestible carbohydrates, also known as fiber, may be fermented by microbial populations along the gastrointestinal tract to synthesize short-chain fatty acids that may be absorbed and metabolized by the pig. These non-digestible carbohydrates include two disaccharides, oligosaccharides, resistant starch, and non-starch polysaccharides. The concentration and structure of non-digestible carbohydrates in diets fed to pigs depend on the type of feed ingredients that are included in the mixed diet. Cellulose, arabinoxylans, and mixed linked β-(1,3) (1,4)-D-glucans are the main cell wall polysaccharides in cereal grains, but vary in proportion and structure depending on the grain and tissue within the grain. Cell walls of oilseeds, oilseed meals, and pulse crops contain cellulose, pectic polysaccharides, lignin, and xyloglucans. Pulse crops and legumes also contain significant quantities of galacto-oligosaccharides including raffinose, stachyose, and verbascose.
    [Show full text]
  • Impact of Glycosidic Bond Configuration on Short Chain Fatty
    nutrients Article Impact of Glycosidic Bond Configuration on Short Chain Fatty Acid Production from Model Fermentable Carbohydrates by the Human Gut Microbiota Hannah C. Harris 1,2, Christine A. Edwards 1 and Douglas J. Morrison 2,* 1 School of Medicine, Dentistry and Nursing, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow G31 2ER, UK; [email protected] (H.C.H.); [email protected] (C.A.E.) 2 Scottish Universities Environmental Research Centre, University of Glasgow, Glasgow G75 0QF, UK * Correspondence: [email protected]; Tel.: +44-135-527-0134 Received: 17 October 2016; Accepted: 22 December 2016; Published: 1 January 2017 Abstract: Short chain fatty acids (SCFA) are the major products of carbohydrate fermentation by gut bacteria. Different carbohydrates are associated with characteristic SCFA profiles although the mechanisms are unclear. The individual SCFA profile may determine any resultant health benefits. Understanding determinants of individual SCFA production would enable substrate choice to be tailored for colonic SCFA manipulation. To test the hypothesis that the orientation and position of the glycosidic bond is a determinant of SCFA production profile, a miniaturized in vitro human colonic batch fermentation model was used to study a range of isomeric glucose disaccharides. Diglucose α(1-1) fermentation led to significantly higher butyrate production (p < 0.01) and a lower proportion of acetate (p < 0.01) compared with other α bonded diglucoses. Diglucose β(1-4) also led to significantly higher butyrate production (p < 0.05) and significantly increased the proportions of propionate and butyrate compared with diglucose α(1-4) (p < 0.05).
    [Show full text]
  • Chapter 6 Carbohydrates Outline 6.1 Classes of Carbohydrates 6.1
    2/25/2015 Outline Lecture Presentation • 6.1 Classes of Carbohydrates • 6.2 Functional Groups in Monosaccharides Chapter 6 • 6.3 Stereochemistry in Monosaccharides Carbohydrates • 6.4 Reactions of Monosaccharides • 6.5 Disaccharides • 6.6 Polysaccharides Julie Klare • 6.7 Carbohydrates and Blood Fortis College Smyrna, GA © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. 6.1 Classes of Carbohydrates 6.1 Classes of Carbohydrates • The simplest carbohydrates are • Disaccharides consist of two monosaccharide monosaccharides (mono is Greek for “one,” units joined together. sakkhari is Greek for “sugar”). • A disaccharide can be split into two • These often sweet-tasting sugars cannot be monosaccharide units. Ordinary table sugar, broken down into smaller carbohydrates. sucrose, C12H22O11, is a disaccharide that can be broken up, through hydrolysis, into the • The common carbohydrate glucose, C6H12O6, is a monosaccharide. monosaccharides glucose and fructose. • Monosaccharides contain carbon, hydrogen, • Oligosaccharidesare carbohydrates and oxygen and have the general formula containing three to nine monosaccharide units. The blood-typing groups known as ABO are Cn(H2O)n, where n is a whole number 3 or higher. oligosaccharides. © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. 6.1 Classes of Carbohydrates 6.1 Classes of Carbohydrates • When 10 or more monosaccharide units are joined together, the large molecules that result are polysaccharides (poly is Greek for “many”). • The sugar units can be connected in one continuous chain or the chain can be branched. • Starch, a polysaccharide in plants, contains branched chains of glucose that can be broken down to produce energy. © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. 1 2/25/2015 6.1 Classes of Carbohydrates 6.1 Classes of Carbohydrates FIBER IN YOUR DIET FIBER IN YOUR DIET • Dietary fibers are carbohydrates that we cannot digest • Insoluble fibers do not mix with water, although they with our own enzymes.
    [Show full text]