Polysaccharides (/ˌpɒliˈsækəraɪd/) are polymeric carbohydrate molecules composed of long chains of monosaccharide units bound together by glycosidic linkages, and on hydrolysis give the constituent monosaccharides or oligosaccharides. They range in structure from linear to highly branched. Examples include storage polysaccharides such as starch and glycogen, and structural polysaccharides such as cellulose and chitin.
Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure, these macromolecules can have distinct properties from their monosaccharide building blocks. They may be amorphous or even insoluble in water. When all the monosaccharides in a polysaccharide are the same type, the polysaccharide is called a homopolysaccharide or homoglycan, but when more than one type of monosaccharide is present they are called heteropolysaccharides or heteroglycans.
Natural saccharides are generally of simple carbohydrates called monosaccharides with general formula (CH2O)n where n is three or more. Examples of monosaccharides are glucose, fructose, and glyceraldehyde. Polysaccharides, meanwhile, have a general formula of Cx(H2O)y where x is usually a large number between 200 and 2500. When the repeating units in the polymer backbone are six-carbon monosaccharides, as is often the case, the general formula simplifies to (C6H10O5)n, where typically 40≤n≤3000.
As a rule of thumb, polysaccharides contain more than ten monosaccharide units, whereas oligosaccharides contain three to ten monosaccharide units; but the precise cutoff varies somewhat according to convention. Polysaccharides are an important class of biological polymers. Their function in living organisms is usually either structure- or storage-related. Starch (a polymer of glucose) is used as a storage polysaccharide in plants, being found in the form of both amylose and the branched amylopectin. In animals, the structurally similar glucose polymer is the more densely branched glycogen, sometimes called "animal starch". Glycogen's properties allow it to be metabolized more quickly, which suits the active lives of moving animals.
Cellulose and chitin are examples of structural polysaccharides. Cellulose is used in the cell walls of plants and other organisms, and is said to be the most abundant organic molecule on Earth. It has many uses such as a significant role in the paper and textile industries, and is used as a feedstock for the production of rayon (via the viscose process), cellulose acetate, celluloid, and nitrocellulose. Chitin has a similar structure, but has nitrogen-containing side branches, increasing its strength. It is found in arthropod exoskeletons and in the cell walls of some fungi. It also has multiple uses, including surgical threads. Polysaccharides also include callose or laminarin, chrysolaminarin, xylan, arabinoxylan, mannan, fucoidan and galactomannan.
Nutrition polysaccharides are common sources of energy. Many organisms can easily break down starches into glucose; however, most organisms cannot metabolize cellulose or other polysaccharides like chitin and arabinoxylans. These carbohydrate types can be metabolized by some bacteria and protists. Ruminants and termites, for example, use microorganisms to process cellulose.
Even though these complex polysaccharides are not very digestible, they provide important dietary elements for humans. Called dietary fiber, these carbohydrates enhance digestion among other benefits. The main action of dietary fiber is to change the nature of the contents of the gastrointestinal tract, and to change how other nutrients and chemicals are absorbed. Soluble fiber binds to bile acids in the small intestine, making them less likely to enter the body; this in turn lowers cholesterol levels in the blood. Soluble fiber also attenuates the absorption of sugar, reduces sugar response after eating, normalizes blood lipid levels and, once fermented in the colon, produces short-chain fatty acids as byproducts with wide-ranging physiological activities (discussion below). Although insoluble fiber is associated with reduced diabetes risk, the mechanism by which this occurs is unknown.
Not yet formally proposed as an essential macronutrient (as of 2005), dietary fiber is nevertheless regarded as important for the diet, with regulatory authorities in many developed countries recommending increases in fiber intake.
Starch is a glucose polymer in which glucopyranose units are bonded by alpha-linkages. It is made up of a mixture of amylose (15–20%) and amylopectin (80–85%). Amylose consists of a linear chain of several hundred glucose molecules and Amylopectin is a branched molecule made of several thousand glucose units (every chain of 24–30 glucose units is one unit of Amylopectin). Starches are insoluble in water. They can be digested by breaking the alpha-linkages (glycosidic bonds). Both humans and other animals have amylases, so they can digest starches. Potato, rice, wheat, and maize are major sources of starch in the human diet. The formations of starches are the ways that plants store glucose.
Glycogen serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue. Glycogen is made primarily by the liver and the muscles, but can also be made by glycogenesis within the brain and stomach.
Glycogen is analogous to starch, a glucose polymer in plants, and is sometimes referred to as animal starch, having a similar structure to amylopectin but more extensively branched and compact than starch. Glycogen is a polymer of α(1→4) glycosidic bonds linked, with α(1→6)-linked branches. Glycogen is found in the form of granules in the cytosol/cytoplasm in many cell types, and plays an important role in the glucose cycle. Glycogen forms an energy reserve that can be quickly mobilized to meet a sudden need for glucose, but one that is less compact and more immediately available as an energy reserve than triglycerides (lipids).
In the liver hepatocytes, glycogen can compose up to eight percent (100–120 g in an adult) of the fresh weight soon after a meal. Only the glycogen stored in the liver can be made accessible to other organs. In the muscles, glycogen is found in a low concentration of one to two percent of the muscle mass. The amount of glycogen stored in the body—especially within the muscles, liver, and red blood cells—varies with physical activity, basal metabolic rate, and eating habits such as intermittent fasting. Small amounts of glycogen are found in the kidneys, and even smaller amounts in certain glial cells in the brain and white blood cells. The uterus also stores glycogen during pregnancy, to nourish the embryo.
Glycogen is composed of a branched chain of glucose residues. It is stored in liver and muscles.
The structural components of plants are formed primarily from cellulose. Wood is largely cellulose and lignin, while paper and cotton are nearly pure cellulose. Cellulose is a polymer made with repeated glucose units bonded together by beta-linkages. Humans and many animals lack an enzyme to break the beta-linkages, so they do not digest cellulose. Certain animals such as termites can digest cellulose, because bacteria possessing the enzyme are present in their gut. Cellulose is insoluble in water. It does not change color when mixed with iodine. On hydrolysis, it yields glucose. It is the most abundant carbohydrate in nature.
Chitin is one of many naturally occurring polymers. It forms a structural component of many animals, such as exoskeletons. Over time it is bio-degradable in the natural environment. Its breakdown may be catalyzed by enzymes called chitinases, secreted by microorganisms such as bacteria and fungi, and produced by some plants. Some of these microorganisms have receptors to simple sugars from the decomposition of chitin. If chitin is detected, they then produce enzymes to digest it by cleaving the glycosidic bonds in order to convert it to simple sugars and ammonia.
Chemically, chitin is closely related to chitosan (a more water-soluble derivative of chitin). It is also closely related to cellulose in that it is a long unbranched chain of glucose derivatives. Both materials contribute structure and strength, protecting the organism.
Pectins are a family of complex polysaccharides that contain 1,4-linked α-D-galactosyl uronic acid residues. They are present in most primary cell walls and in the non-woody parts of terrestrial plants.
Pathogenic bacteria commonly produce a thick, mucous-like, layer of polysaccharide. This "capsule" cloaks antigenic proteins on the bacterial surface that would otherwise provoke an immune response and thereby lead to the destruction of the bacteria. Capsular polysaccharides are water-soluble, commonly acidic, and have molecular weights on the order of 100–2000 kDa. They are linear and consist of regularly repeating subunits of one to six monosaccharides. There is enormous structural diversity; nearly two hundred different polysaccharides are produced by E. coli alone. Mixtures of capsular polysaccharides, either conjugated or native are used as vaccines.
Bacteria and many other microbes, including fungi and algae, often secrete polysaccharides to help them adhere to surfaces and to prevent them from drying out. Humans have developed some of these polysaccharides into useful products, including xanthan gum, dextran, welan gum, gellan gum, diutan gum and pullulan.
Most of these polysaccharides exhibit useful visco-elastic properties when dissolved in water at very low levels. This makes various liquids used in everyday life, such as some foods, lotions, cleaners, and paints, viscous when stationary, but much more free-flowing when even slight shear is applied by stirring or shaking, pouring, wiping, or brushing. This property is named pseudoplasticity or shear thinning; the study of such matters is called rheology.
|Shear Rate (rpm)||Viscosity (cP)|
Aqueous solutions of the polysaccharide alone have a curious behavior when stirred: after stirring ceases, the solution initially continues to swirl due to momentum, then slows to a standstill due to viscosity and reverses direction briefly before stopping. This recoil is due to the elastic effect of the polysaccharide chains, previously stretched in solution, returning to their relaxed state.
Cell-surface polysaccharides play diverse roles in bacterial ecology and physiology. They serve as a barrier between the cell wall and the environment, mediate host-pathogen interactions, and form structural components of biofilms. These polysaccharides are synthesized from nucleotide-activated precursors (called nucleotide sugars) and, in most cases, all the enzymes necessary for biosynthesis, assembly and transport of the completed polymer are encoded by genes organized in dedicated clusters within the genome of the organism. Lipopolysaccharide is one of the most important cell-surface polysaccharides, as it plays a key structural role in outer membrane integrity, as well as being an important mediator of host-pathogen interactions.
The enzymes that make the A-band (homopolymeric) and B-band (heteropolymeric) O-antigens have been identified and the metabolic pathways defined. The exopolysaccharide alginate is a linear copolymer of β-1,4-linked D-mannuronic acid and L-guluronic acid residues, and is responsible for the mucoid phenotype of late-stage cystic fibrosis disease. The pel and psl loci are two recently discovered gene clusters that also encode exopolysaccharides found to be important for biofilm formation. Rhamnolipid is a biosurfactant whose production is tightly regulated at the transcriptional level, but the precise role that it plays in disease is not well understood at present. Protein glycosylation, particularly of pilin and flagellin, became a focus of research by several groups from about 2007, and has been shown to be important for adhesion and invasion during bacterial infection.
Polysaccharides with unprotected vicinal diols or amino sugars (i.e. some OH groups replaced with amine) give a positive periodic acid-Schiff stain (PAS). The list of polysaccharides that stain with PAS is long. Although mucins of epithelial origins stain with PAS, mucins of connective tissue origin have so many acidic substitutions that they do not have enough glycol or amino-alcohol groups left to react with PAS.
The bacterial capsule is a very large structure of many bacteria. It is a polysaccharide layer that lies outside the cell envelope, and is thus deemed part of the outer envelope of a bacterial cell. It is a well-organized layer, not easily washed off, and it can be the cause of various diseases.
The capsule—which can be found in both gram negative and gram-positive bacteria—is different to the second lipid membrane – bacterial outer membrane, which contains lipopolysaccharides and lipoproteins and is found only in gram-negative bacteria.
When the amorphous viscid secretion (that makes up the capsule) diffuses into the surrounding medium and remains as a loose undemarcated secretion, it is known as slime layer. Capsule and slime layer are sometimes summarized under the term glycocalyx.Conjugate vaccine
Conjugate vaccines combine a weak antigen with a strong antigen so that the immune system has a stronger response to the weak antigen.
Vaccines are used to prevent diseases by invoking an immune response to an antigen, the foreign part of a bacteria or virus that the immune system recognizes. This is usually accomplished with an attenuated or dead version of a pathogenic bacterium or virus in the vaccine, so that the immune system can recognize the antigen later in life. Many vaccines contain a single antigen that the body will recognize.
However, the antigen of some pathogenic bacteria does not elicit a strong response from the immune system, so a vaccination against this weak antigen would not protect the person later in life. In this case, a conjugate vaccine is used in order to invoke an immune system response against the weak antigen. In a conjugate vaccine, the weak antigen is covalently attached to a strong antigen, thereby eliciting a stronger immunological response to the weak antigen. Most commonly, the weak antigen is a polysaccharide that is attached to strong protein antigen. However, peptide/protein and protein/protein conjugates have also been developed.Eustigmatophyte
Eustigmatophytes are a small group (12 genera; ~41 species) of eukaryotic algae that includes marine, freshwater and soil-living species.All eustigmatophytes are unicellular, with coccoid cells and polysaccharide cell walls. Eustigmatophytes contain one or more yellow-green chloroplasts, which contain chlorophyll a and the accessory pigments violaxanthin and β-carotene. Eustigmatophyte zoids (gametes) possess a single or pair of flagella, originating from the apex of the cell. Unlike other heterokontophytes, eustigmatophyte zoids do not have typical photoreceptive organelles (or eyespots); instead an orange-red eyespot outside a chloroplast is located at the anterior end of the zoid.
Ecologically, eustigmatophytes occur as photosynthetic autotrophs across a range of systems. Most eustigmatophyte genera live in freshwater or in soil, although Nannochloropsis contains marine species of picophytoplankton (2–4 μm).
The class was erected to include some algae previously classified in the Xanthophyceae.Haemophilus influenzae
Haemophilus influenzae (formerly called Pfeiffer's bacillus or Bacillus influenzae) is a Gram-negative, coccobacillary, facultatively anaerobic pathogenic bacterium belonging to the Pasteurellaceae family. H. influenzae was first described in 1892 by Richard Pfeiffer during an influenza pandemic.The bacterium was mistakenly considered to be the cause of influenza until 1933, when the viral cause of influenza became apparent, and is still colloquially known as bacterial influenza. H. influenzae is responsible for a wide range of localized and invasive infections. This species was the first free-living organism to have its entire genome sequenced.Hib vaccine
The Haemophilus influenzae type B vaccine, often called Hib vaccine, is a vaccine used to prevent Haemophilus influenzae type b (Hib) infection. In countries that include it as a routine vaccine, rates of severe Hib infections have decreased more than 90%. It has therefore resulted in a decrease in the rate of meningitis, pneumonia, and epiglottitis.It is recommended by both the World Health Organization and Centers for Disease Control and Prevention. Two or three doses should be given before six months of age. In the United States a fourth dose is recommended between 12 and 15 months of age. The first dose is recommended around six weeks of age with at least four weeks between doses. If only two doses are used, another dose later in life is recommended. It is given by injection into a muscle.Severe side effects are uncommon. About 20 to 25% of people develop pain at the site of injection while about 2% develop a fever. There is no clear association with severe allergic reactions. The Hib vaccine is available by itself, in combination with the diphtheria/tetanus/pertussis vaccine, and in combination with the hepatitis B vaccine, among others. All Hib vaccines that are currently used are conjugate vaccine.An initial Hib vaccine was developed in 1977 which was replaced by a more effective formulation in the 1990s. As of 2013, 184 countries include it in their routine vaccinations. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. The wholesale cost of a pentavalent vaccine which includes Hib in the developing world was US$15.40 per dose as of 2014. In the United States it costs about $25–50 per dose.Levan polysaccharide
Levans are a group of fructans; polymers of fructose forming a non-structural carbohydrate, which in the case of levans can themselves link to form super-molecules comprising even hundreds of thousands.
The shortest levan is 6-kestose, essentially a chain of two fructose molecules and a terminal glucose molecule. Levans are produced in almost all bacterial versions of fructan production, as well as being possible to produce by fracturing soybean mucilage.Lipopolysaccharide
Lipopolysaccharides (LPS), also known as lipoglycans and endotoxins, are large molecules consisting of a lipid and a polysaccharide composed of O-antigen, outer core and inner core joined by a covalent bond; they are found in the outer membrane of Gram-negative bacteria.
The term lipooligosaccharide ("LOS") is used to refer to a low-molecular-weight form of bacterial lipopolysaccharides.Mannan
Mannan may refer to a plant polysaccharide that is a linear polymer of the sugar mannose. Plant mannans have β(1-4) linkages. It is a form of storage polysaccharide. Ivory nut is a source of mannan.
Mannan may also refer to a cell wall polysaccharide found in yeasts. This type of mannan has a α(1-6) linked backbone and α(1-2) and α(1-3) linked branches. It is serologically similar to structures found on mammalian glycoproteins.
Detection of mannan leads to lysis in the mannan-binding lectin pathway. This mannan is the source of MOS used as prebiotics in animal husbandry and nutritional supplements.Neisseria meningitidis
Neisseria meningitidis, often referred to as meningococcus, is a Gram-negative bacterium that can cause meningitis and other forms of meningococcal disease such as meningococcemia, a life-threatening sepsis. It has also been reported to be transmitted through oral sex and cause urethritis in men. The bacterium is referred to as a coccus because it is round, and more specifically, diplococcus because of its tendency to form pairs. About 10% of adults are carriers of the bacteria in their nasopharynx. As an exclusively human pathogen it is the main cause of bacterial meningitis in children and young adults, causing developmental impairment and death in about 10% of cases. It causes the only form of bacterial meningitis known to occur epidemically, mainly Africa and Asia. It occurs worldwide in both epidemic and endemic form.N. meningitidis is spread through saliva and respiratory secretions during coughing, sneezing, kissing, chewing on toys and even through sharing a source of fresh water. It infects its host cells by sticking to them with long thin extensions called pili and the surface-exposed proteins Opa and Opc and has several virulence factors.Neocallimastigomycota
Neocallimastigomycota is a phylum containing anaerobic fungi, which are symbionts found in the digestive tracts of larger herbivores. Anaerobic fungi were originally placed within phylum Chytridiomycota, within Order Neocallimastigales but later raised to phylum level, a decision upheld by later phylogenetic reconstructions. It encompasses only one family.NmVac4-A/C/Y/W-135
NmVac4-A/C/Y/W-135 is the commercial name of the Meningococcal meningitis polysaccharide serogroups A,C,Y and W-135 vaccine of JN-International Medical Corporation. The product is specially designed and formulated to be used in developing countries for protecting populations during meningitis disease epidemics. Meningococcal meningitis is a bacterial infection caused by the bacterium Neisseria meningitidis, also known as meningococcus. The vaccine is made from bacterial capsular polysaccharides through fermentation of each individual serogroup of Neisseria meningitidis in bioreactors. Then the polysaccharides are purified, formulated and lyophilized using preservatives and stabilizers to make a vaccine product. The vaccine cannot protect other than Neisseria meningitidis serogroups A,C,Y and W-135 or cannot completely protect from these serogroups.Pneumococcal polysaccharide vaccine
Pneumococcal polysaccharide vaccine (PPSV)—the latest version known as Pneumovax 23 (PPV-23)—is the first pneumococcal vaccine derived from a capsular polysaccharide, and an important landmark in medical history. The polysaccharide antigens were used to induce type-specific antibodies that enhanced opsonization, phagocytosis, and killing of Streptococcus pneumoniae (pneumococcal) bacteria by phagocytic immune cells. The pneumococcal polysaccharide vaccine is widely used in high-risk adults. As a result, there have been important reductions in the incidence, morbidity, and mortality from invasive pneumococcal disease.
First used in 1945, the tetravalent vaccine was not widely distributed, since its deployment coincided with the discovery of penicillin. In the 1970s, Robert Austrian championed the manufacture and distribution of a 14-valent PPSV. This evolved in 1983 to a 23-valent formulation (PPSV23). A significant breakthrough affecting the burden of pneumococcal disease was the licensing of a protein conjugate heptavalent vaccine (PCV7) beginning in February 2000.Pneumococcal vaccine
Pneumococcal vaccines are vaccines against the bacteria Streptococcus pneumoniae. Their use can prevent some cases of pneumonia, meningitis, and sepsis. There are two types of pneumococcal vaccines: conjugate vaccines and polysaccharide vaccines. They are given by injection either into a muscle or just under the skin.The World Health Organization recommends the use of the conjugate vaccine in the routine immunizations given to children. This includes those with HIV/AIDS. The recommended three or four doses are between 71 and 93% effective at preventing severe pneumococcal disease. The polysaccharide vaccines, while effective in healthy adults, are not effective in children less than two years old or those with poor immune function.These vaccines are generally safe. With the conjugate vaccine about 10% of babies develop redness at the site of injection, fever, or change in sleep. Severe allergies are very rare.The first pneumococcal vaccine was developed in the 1980s. They are on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. The wholesale cost in the developing world is about US$17 per dose as of 2014. In the United States it is between US$25 and US$100.Polysaccharide-K
Polysaccharide-K (Krestin, PSK) is a protein-bound polysaccharide isolated from the fruitbody of Trametes versicolor.Schizophyllan
Schizophyllan (Sonifilan, SPG) is a neutral extracellular polysaccharide produced by the fungus Schizophyllum commune. Schizophyllan is a β-1,3 beta-glucan with β-1,6 branching. Schizophyllan is also known as sizofiran.
Schizophyllan has a molecular weight of 450,000 Da, and a specific rotation in water of +18-24°. A chemically analogous polysaccharide, scleroglucan, is formed by the fungus Athelia rolfsii. Both polysaccharides share the chemical structure of the backbone with curdlan. It is known for several things, including its ability to stimulate the immune system, carry metals in water, aid in delivering drugs, and use in some nanofibers.Sequencing
In genetics and biochemistry, sequencing means to determine the primary structure (sometimes incorrectly called the primary sequence) of an unbranched biopolymer. Sequencing results in a symbolic linear depiction known as a sequence which succinctly summarizes much of the atomic-level structure of the sequenced molecule.Streptococcus pneumoniae
Streptococcus pneumoniae, or pneumococcus, is a Gram-positive, alpha-hemolytic (under aerobic conditions) or beta-hemolytic (under anaerobic conditions), facultative anaerobic member of the genus Streptococcus. They are usually found in pairs (diplococci) and do not form spores and are nonmotile. As a significant human pathogenic bacterium S. pneumoniae was recognized as a major cause of pneumonia in the late 19th century, and is the subject of many humoral immunity studies.
S. pneumoniae resides asymptomatically in healthy carriers typically colonizing the respiratory tract, sinuses, and nasal cavity. However, in susceptible individuals with weaker immune systems, such as the elderly and young children, the bacterium may become pathogenic and spread to other locations to cause disease. It spreads by direct person-to-person contact via respiratory droplets and by autoinoculation in persons carrying the bacteria in their upper respiratory tracts. It can be a cause of neonatal infections.S. pneumoniae is the main cause of community acquired pneumonia and meningitis in children and the elderly, and of septicemia in those infected with HIV. The organism also causes many types of pneumococcal infections other than pneumonia. These invasive pneumococcal diseases include bronchitis, rhinitis, acute sinusitis, otitis media, conjunctivitis, meningitis, sepsis, osteomyelitis, septic arthritis, endocarditis, peritonitis, pericarditis, cellulitis, and brain abscess.S. pneumoniae can be differentiated from the viridans streptococci, some of which are also alpha-hemolytic, using an optochin test, as S. pneumoniae is optochin-sensitive. S. pneumoniae can also be distinguished based on its sensitivity to lysis by bile, the so-called "bile solubility test". The encapsulated, Gram-positive, coccoid bacteria have a distinctive morphology on Gram stain, lancet-shaped diplococci. They have a polysaccharide capsule that acts as a virulence factor for the organism; more than 90 different serotypes are known, and these types differ in virulence, prevalence, and extent of drug resistance.Sugars in wine
Sugars in wine are at the heart of what makes winemaking possible. During the process of fermentation, sugars from wine grapes are broken down and converted by yeast into alcohol (ethanol) and carbon dioxide. Grapes accumulate sugars as they grow on the grapevine through the translocation of sucrose molecules that are produced by photosynthesis from the leaves. During ripening the sucrose molecules are hydrolyzed (separated) by the enzyme invertase into glucose and fructose. By the time of harvest, between 15 and 25% of the grape will be composed of simple sugars. Both glucose and fructose are six-carbon sugars but three-, four-, five- and seven-carbon sugars are also present in the grape. Not all sugars are fermentable with sugars like the five-carbon arabinose, rhamnose and xylose still being present in the wine after fermentation. Very high sugar content will effectively kill the yeast once a certain (high) alcohol content is reached. For these reasons, no wine is ever fermented completely "dry" (meaning without any residual sugar). Sugar's role in dictating the final alcohol content of the wine (and such its resulting body and "mouth-feel") sometimes encourages winemakers to add sugar (usually sucrose) during winemaking in a process known as chaptalization solely in order to boost the alcohol content – chaptalization does not increase the sweetness of a wine.Vi capsular polysaccharide vaccine
Not to be confused with Ty21a. For an overview of vaccines against typhoid fever, see Typhoid vaccine.
The Vi capsular polysaccharide vaccine (or ViCPS) is one of two vaccines recommended by the World Health Organization for the prevention of typhoid (the other is Ty21a). The vaccine was first licensed in the US in 1994 and is made from the purified Vi capsular polysaccharide from the Ty2 Salmonella Typhi strain; it is a subunit vaccine. A newer conjugate form of the vaccine (Vi bound to a non-toxic recombinant Pseudomonas aeruginosa exotoxin, or Vi-rEPA) has enhanced efficacy, including protection of children under 5 years of age.
Types of carbohydrates