In this presentation, we are going to study biochemically important carbohydrates. Here are our agenda. Monossaccharides, disaccharides, and oligosaccharides, polysaccharides, and dietary considerations regarding carbohydrates. First would be some biochemically important monossaccharides. dlucose um which is also called dextrose or blood sugar or grape sugar. Ripe fruits particularly ripe grapes are a good source of glucose which is often referred as a grape sugar. Dextrose is an optically active dlucose in aquous solution. uh it rotates plain polarized light to the right and it is considered to be a blood sugar from the fact that blood contains dissolved glucose. So it is also the most abundant in nature and most important on a human nutritional standpoint. It is actually used by our cells or the cells of living organisms as a primary source of energy. The glucose as a blood sugar actual glucose concentration in the blood is actually dependent on the time that has elapsed since the last meal was eaten. So um for its normal concentration it is about 70 to 100 mg per deciliter of blood and it rises to about 130 mg per deciliter after the first hour of eating. So the concentration will decrease over the next 2 to three hours going back to the normal range. A 5% mass pervol glucose solution is often used in hospitals as an intravenous source of nourishment for patients who cannot take food by mouth. So for example, if you get admitted in the hospital and you would have an IV insertion, this is the liquid that goes straight to your veins to avoid being dehydrated and as your energy source because the body can use it as an energy source even without digesting it. Next biochemically important monossaccharide is the dalactose. So as you can see on the right part upper right part of the screen that is the hero's projection structure for the galactose it is synthesized from glucose in memory glands for use in lactose in the human body and it can be converted into glucose. It can be found in dairy products, sugar beets and other gums and mucilages. So sometimes it is also called the brain sugar because it is a component of glyoproteins found in our brain and nerve tissues. It is also present in chemical markers that distinguish various types of blood. Next would be the fructose. Defucructose is a basic component of table sugar and biochemically it is the most important ketoexose. It is also known as levos and fruit sugar which is found naturally in fruits, some vegetables and honey. It can also be found in corn syrup and sometimes it can be used as a dietary sugar because um less is needed for the same amount of sweetness. So if for example you buy um beverages or other processed foods and you look at their um ingredients and you find HFCS so it pertains to high fructose corn syrup which is used to sweeten this products. Another biochemically important monossaccharide is uh dribbos. It is a component of a variety of complex molecules which include our RNAs and DNA and also the energy rich compound such as ATP or the adenosine triphosphate disaccharides and oligosaccharides. Before we discuss some important disaccharides and oligosaccharides, let us first discuss how disaccharides and oligosaccharides and polyaccharides are being formed. So let us start with the disaccharides. Now in disaccharides it is composed of two monossaccharide unit connected by a glycosidic linkage. So this two monossaccharides one will act or will function as a hemi acetyl. So the one on the left and the other one will function as an alcohol. When this two condenses or combine together, so the reaction is a condensation reaction. A glycosidic linkage is formed. So it is a bond between two monossaccharides resulting from the reaction between the hemi acetyl carbon atom alcohol group of one monossaccharide and an alcohol group on the other monossaccharide together with a condensation reaction leading to the formation of disaccharides. Water will be the byproduct. Now first for our biochemically important disaccharide we have maltos as you can see from the image depicted on the screen. Maltose is a disaccharide composed of 2D glucose units. Malto bios or malt malt sugar is another term for maltos. So it is produced when starch breakdowns. The breaking down of starch takes place when seeds germinate and in us humans during starch digestion. It is also a common ingredient found in baby foods and in molted milk. Here shows how maltos is formed. So you have an alpha dlucose and another dlucose whose configuration can either be an alpha or beta configuration. When these two glucose units condenses an alpha 1 to4 glycosidic linkage is formed. So if you notice um glycosidic linkages have specific names. So this one has an alpha 14 uh linkage as its name because the configuration of the monossaccharide on the left is an alpha configuration. And then what is being connected by the glycosidic linkage is the carbon number one from the hemi acetyl monossaccharide and carbon number four of the other monossaccharide. The glucose unit on the right of maltos can open and close. So it is in equilibrium with its open chain aldihide form. So what does it mean? It means that there are actually three forms of the maltos molecule. So you have the alpha maltos, the beta maltos and the open chain maltos. In the solid state the beta form is the one that is dominant. The most important chemical reaction of maltos or disaccharides in general is hydrarolysis. So what is hydrarolysis? That is simply the reverse of condensation or the reverse on how disaccharides are formed. So in hydraysis the glycosidic linkage is hydrayed with a with the presence of water and an enzyme and it will be hhydraized into its component monossaccharides which this time is to the uh glucose units. Here are some food sources of maltos. So we have sweet potato, honey, peaches, spelt which is a species of wheat, bagels or bread roll which originate in the uh Jewish communities in Poland. Traditionally it is made from yeasted wheat dough and we also and we also have bread then broccoli um have has malttos as well molasses which is a viscous byproduct obtained from the refining of sugar cane or sugar beet juice into sugar and we have food products sold in the market like for example cocoa crunch and milo and other energy bars which contain maltos Cellubios another important disaccharide is produced as an intermediate when cellulose undergoes hydraysis. So if you notice it also contains two dlucose units and the other one having or it must have a beta configuration. Now the change in configuration on the dlucose on the left results into a beta 1 to4 glycoidic linkage. It is a reducing sugar and it also has three isomeic forms in aqua solution. When hydrayzeed it will also produce two dlucose molecules. So if you notice structurally cellios and malttodos has a lot of similarities but because of the difference in the configuration of one of the glucose molecule components it will also result in a different glycosidic linkage which will result to uh these two disaccharides behaving differently from each other. Now the enzyme that breaks the glycosidic linkage in malttos which is maltise is an enzyme that can be found in both humans and in yeast. However uh the enzyme that can hydrayze the glycosidic linkage of cellios which is cellbas is an enzyme that cannot be found neither in humans nor in yeast. So which means that we cannot digest cellios and it cannot be fermented by yeast. Lactose is made up of a beta dalactose unit and an alpha dl glucose unit which is joined by a beta 1 to4 glycoidic linkage. Now this is a reducing sugar and this is a major sugar found in milk. In mamalian memorary glands the enzymes take glucose from the bloodstream and then synthesize lactose in a four-step process. Lactose is an important ingredient in commercially produced infant formulas that are designed to simulate mother's milk. Now the souring of milk is caused by the conversion of lactose into lactic acid by bacteria in milk. So pasteurization is done which is a quick heating process that would kill most of the bacteria and will the souring process. Lactose can be hydrayed by acid or by the enzyme lactase forming an equimar mixture of galactose and glucose. Meaning when lactose is broken down by the enzyme lactase, it produces an equal amount of galactose and glucose. In the human body, the galactose produced is then converted to glucose by other enzymes. So we know that it is the principal carbohydrate in milk. And as comparison, human mother's milk contains 78% lactose as compared to 4 to 5% lactose found in cow's milk. Here are foods rich in lactose. So cow's milk and goats milk. Then we have u milk byproducts like yogurt, kefir, cheese and ice cream. Lactose intolerance and lactose persistence. So what do we mean by lactose intolerance and lactose persistence? For many people, the digestion and absorption of lactose are a problem. So take note that normal lactose intolerance is actually not considered to be a food allergy situation. Because when we say food allergies, it actually arises when um one's immune system responds to a foreign substance or tagged by uh the immune system as an invading allergen. Lactose intolerance does not actually involve the immune system. So it is a condition wherein people lacking the enzyme lactase which is needed to hydrayze lactose to galactose and glucose. Here are the estimated prevalence of lactase persistence in various populations. So as we can see from this uh diagram um we have Sweden as uh having 99% lactase persistence, Scotland. So Denmark these are countries whose products are milk based and they consume a lot of milk products. Another important disaccharide would be sucrose or what we know as stable sugar. It is from juice of sugar cane and sugar beets and sugar cane is 20% by mass sucrose. So sucrose is the most abundant of all disaccharides and of course throughout the plant kingdom while sugar beets contain 70 17% by mass sucrose. So sucrose is composed of two monossaccharides. So we have a an alpha dlucose and a betal fructose connected together by an alpha beta 1 to2 linkage. Now sucrose unlike maltos and cellios and lactose is what we have seen from the previous slides their structure. Sucrose is actually a non-reducing sugar. Sucrease is the enzyme needed to break the alpha beta 1 to2 linkage in sucrose and it is present in the human body. So that is the reason why sucrose is an easily digested substance. When sucrose is hydrayed it produces again an equal mixture an equal concentration for the mixture of glucose and fructose which will now be called an invert sugar. So when sucrose is cooked with acid containing foods like for example fruits or berries what takes place is partial hydraysis forming some invert sugar. So jams and jellies which are prepared in this manner are actually sweeter than the pure sucrose added to the original mixture because onetoone mixtures of glucose and fructose taste sweeter than sucrose. Here are some sugar substitutes that is currently being marketed or circulated. So we have saccharine, sucralose, aspartame and neotame. Among the sugar substitutes, saccharine is oldest of the artificial sweeteners. It has been in use for more than a hundred years. It is 300 times sweeter than sucrose and examples of its of how it's marketed. It is named as sweet and low and sugar tween both saccharine based commercial products. Questions about its safety arose in 1977 after a study suggested that large doses of it could cause bladder tumors in rats. So as a result the FDA proposed banning saccharine but public support for its use caused Congress to impose a moratorum on the ban. So in 1991 on the basis of many further studies the FDA withdrew its proposal to ban saccharine. Another sugar substitute is aspartame marketed as neutrieet. It accounts for three4s of current sugar substitute use. It is 180 times sweeter than sucrose. So, it is used mostly um in the United States and Canada. It has quickly found its way into almost every diet food on the market today. Aspartame just like saccharine are not heat stable and therefore it cannot be used in products that require cooking. The safety of aspartame lies with its hydraysis products. So when aspartame is hydrayed it produces the amino acids aspartic acid and phenol alanine. This amino acids are identical to those obtained from digestion of proteins. The only danger aspart aspartane poses is that it contains phenol alanine an amino acid that can lead to mental retardation among young children suffering from fennyl ketonoria. Sucralose is a derivative of sucrose. It is heat stable. So that is its advantage with aspartame. It can be used in cooking food or in cooked food. It is 600 times sweeter than sucrose and is calorief free. Aspartame loses its sweetness when heated while sucralose does not. It is calorie free and cannot be hydrayed as it passes through the digestive tract. Neotame, a generalpurpose sweetener, is already also heat stable. It can be used in a wide variety of products including baked goods, frostings, frozen desserts, puddings, and fruit juices. Its sweetness is 7,000 times greater than that of sucrose. So only a small amount is needed to sweetened products. So its caloric impact is also negligible. It is aspartame derivative. Ooligosaccharides. Um, oligosaccharides contain three to 10 monsaccharide units bonded to each other through a glycosidic linkage. Raffinos, the one on the left, and stakios, the one on the right, are two naturally occurring oligosaccharides commonly found in cabbages, onions, broccoli, Brussels sprouts, whole wheat grain, and all types of beans. The monossaccharide components of the tricaccharide rafinos are galactose um dlucose and uh beta d fructose. Stakio is a tetraaccharide which contains an additional galactose unit as compared to the structure of rafinos. Now take a look at the glycosidic linkages present on both. Now humans lack the needed enzyme to metabolize either rafinos or stacio. When this oligosaccharides are ingested in food, they pass undigested into the large intestine where uh bacteria act upon them. This bacterial action is what causes discomfort and flatulence. In biochemical systems, it is more common to encounter oligosaccharides as components of more complex molecules rather than like rafinos and stakio which are in their free state. Human blood is classified into four types. So we have type A, type B, type A B and type O. Now what determines the type of blood a person has is the oligosaccharide that is attached to the person's red blood cells. Now the biochemical basis for the various types of blood involves oligosaccharide molecules that are attached to the plasma membrane of red blood cells. Now this oligosaccharide attachments which we would be calling biochemical markers are of three different for formulations. One is a tetraaccharide and the other two are pentaccharides. Four monossaccharides contribute to the makeup of the oligosaccharide marking system. So one we have alpha de galactose then we have alpha lfucose alpha n acetyl dl glucosamine and alpha n acetyl d galactosamine. So of these four one is a simple monossaccharide that is the alpha dalactose and the other three are monossaccharide derivatives. Now note that all the oligosaccharide markers have a common for monossaccharide sequence in their structure. Now what will determine the blood type is the absence or presence of a fifth monossaccharide unit. Type O if we will look at the um representation on the screen lacks a fifth monossaccharide unit. Type A blood has an acetyl galactose amine as a fifth unit. Type B blood has a galactose fifth unit. And type A B will contain both type A and type B markers. If a blood transfusion is necessary and the patient's own blood is not available, then we look for donors, right? So the donor's blood must be matched to that of the patient. Blood of one type cannot be given to a recipient with blood of another type unless these two types are compatible. What will happen if there would be wrong blood type and the transfusion is done? So it can cause the blood cells to form clumps which will be a potentially fatal reaction. Now in this table we can see the compatibility relationships of the different blood types. So people for example with type O blood are universal donors and those with type AB blood are universal recipients. Another oligosaccharide would be solinine. So if you will notice on the screen, these are examples or these are potatoes. Now many plants including potato produce toxins as their defense mechanism against insects and predators. The small amount of solenine present in properly stored potatoes is not dangerous and actually contributes to the flavor of the potatoes. However, when there is an excessive amount of solenine, potatoes will taste bitter. Solenine amounts in potatoes increase when potatoes sprout and when they are exposed to sunlight. Improperly stored potatoes would have that greenish color which develops in their skin and the flesh under the skin. Such grinning is a warning already that solinin levels are higher than normal and may even mean that there it's approaching to an unhealthy level. The green color is not actually solenine but it is chlorophyll. Sunlight exposure stimulates both solenine and chlorophyll production. So peeling potatoes deeply to remove the green color also removes excess solenine. Sprouts need to be removed and potato ice need to be cut out. Sprouts also have high solenine content. So if you see your potatoes having sprouts already, so that means the solenine level is already increasing. So you must remove that. um so that it won't taste bitter and that it won't have any after effect. Deep frying reduces solinine levels while boiling is ineffective in decreasing such levels. The tricaccharide present in soline is composed of the monossaccharides dlucose dalactose and um a rarely encountered monossaccharide which is Lram nose. Lramm nose is unusual since it is the L isomer wherein D isomers are commonly present in nature and if you will look at the structure it contains a methyl group on carbon number six rather than the CH2O group. Now we move forward to polysaccharides. Unlike monossaccharides and most disaccharides, polysaccharides are not sweet and they will not test positive in tolerance and benedict solutions for reducing sugars. They also have limited water solubility because of their very large size. Polysaccharides can also be called as glycans. What are the important parameters that distinguish polysaccharides? First the identity of the monossaccharide repeating units in the polymer chain. So we have here the unbranched homopolyaccharides and the branched homopolysaccharides unbranched heteropolysaccharides and branched heteropolysaccharides. Now what is a homopolysaccharide? So when we say homopolysaccharide this is a polysaccharide wherein only one type of monossaccharide monomer is present. So for example in an unbranched homopolysaccharide all the monossaccharide components are that of glucose. Now when there is branching then we call that a branched homopolysaccharide. So therefore a heteropolyaccharide is a a polysaccharide in which more than one so usually two type of monossaccharide monomer is present in the chain. Next the length of the polymer chain. So it vary from less than 100 to over 50,000 monomer units. And then the type of glycosidic linkage present between monomer units. The degree of branching of the polymer is also another important parameter that will distinguish polysaccharides from each other. The ability to form branch chain structures distinguishes polysaccharides from the other two major types of biochemical polymers um the proteins and the nucleic acids which only um occur as linear or unbranched polymers. What are the different types of polysaccharides? We have three. We're going to discuss three. So we have the storage polysaccharides, the structural polysaccharides and the acidic polysaccharides. A storage polysaccharide is a polysaccharide that is a storage form of monossaccharides and is used as an energy source in cells. So we have starch and glycogenet homopolysaccharide containing only glucose monossaccharide units that is starch. So um starch can be branched and unbr unbranched energy storage polysaccharide in plants. Now if excess glucose enters a plant cell it will be converted to starch and then it will be stored for later use. When the cell cannot get enough glucose from outside the cell it hydrayes starch to um release the glucose. Two different polyucose polysaccharides can be isolated from most starches. So that would be the amos which is the unbranched um homopolysaccharide and amalopectin which is the branched homopolyaccharide um amos uh unbranched and usually accounts for 15 to 20% of the starch and the type of glycosidic linkage present is the alpha 14. The number of glucose units present in an amalos chain depends on the source of starch. 300 to 500 monomer units are usually present in the uh amos chain. Amalopectin on the other hand is a branched glucose polymer. It accounts for the remaining 80 to 85% of the starch. A branch occurs about once every 25 to 30 glucose units and the branch points involve um alpha 1 to six linkages. Because of the branching uh amalopectin has a larger average molecular mass compared with a linear amos. Up to 100,000 glucose units may be present in the amalopectin polymer chain. The starches present in uh potatoes and cereal grains account for approximately 2/3 of the world's food consumption. One test to identify the presence of starch is the iodine test. Iodine is often used to test for the presence of starch in solution. So starch containing solutions will turn dark blue black when iodine is added just like um what you have observed when you did the iodine test or the starch test in the biochemistry laboratory. Another storage polysaccharide which is found in animals is glycogen. So its structure is similar somewhat similar to that of of amalopectin. Glycosidic linkages present are alpha 1 to4 and alpha 1 to6. It's three times more highly branched compared to amalopectin and it is much larger with up to a million glucose units present. So its function is similar to that of starch in plants and it is sometimes referred to as animal starch. When excess glucose is present in the blood, normally for example, if we eat too much starch, the liver and muscle tissues will convert excess glucose to glycogen, which will then be stored in the tissues. Now, whenever the glucose blood level drops, like for example, when you are doing exercise or when you fast or even by doing normal activities, some stored glycogen is hydrayed back into glucose. Structural polysaccharides. These are polysaccharides that serve as structural elements in plant cell walls and animal exoskeletons. So we have cellulose. This is the structural component of plant cell walls and branched glucose polymer. Um glucose residues in the beta configuration. So the glycosidic linkage present is a beta 1 to4. The woody portion of plants like the stems, the stocks and the trunk. it uh they have particularly high concentrations of this fibrous water insoluble substance. So a cellulose polymer chain contains about 5,000 glucose units. Cotton if we would look at its component is almost pure cellulose. So around uh about 90 to 95% cellulose while wood is about 50% or 35 to 45% cellulose. Cellulose fibrills are formed due to extensive hydrogen bonding within and between cellulose chains. So these are insoluble in water and are quite strong and rigid. Even though it is a glucose polymer, it is not a it cannot be a source of nutrition for human beings. So the reason for that is because we lack the enzymes capable of catalyzing the hydrarolysis of its glycosidic linkage. Now even grazing animals they also lack the enzymes necessary for its breakdown. However found in their intestinal tracts are like for example the horses, the cows and the sheep. They contain bacteria that produce cellulace the enzyme that can hydrayze cellulose glycosidic linkages. Now the intestinal tracts of termites contain the same microorganisms which enables termites to use wood as their source of food. So despite its nondigestibility, cellulose is still an important component of a balanced diet because it serves as a dietary fiber. Another structural polysaccharide. So these are for animals or the insects. Um we have kitine. Uh structurally kiten is identical to cellulose except that if you would look at it the monossaccharide present in the um in kitine is a glucose derivative. So which we call the nacetyl dlucosamine or nag rather than the dlucose itself. So it's probably the second most abundant organic compound on earth. It is a structural homoglycan found in the exoskeletons of insects and crustaceians and also in the cell walls of most fungi and many algae. The product of complete hydraysis of kitine is dlucosamine. It is marketed now as a dietary supplement which is claimed to help with joint problems. However, there are also claims that delucosamine decreases joint inflammation and pain associated with osteoarthritis have yet to be substantiated. Acidic polysaccharides are polyaccharides with a disaccharide repeating unit wherein one of its disaccharide components. So this is a heteropolyaccharide is an amino sugar and one or both disaccharide components has a negative charge because of the presence of a sulfate group or a caroxile group. Two of the most well-known acidic polysaccharides are what we are going to discuss which are hyaluronic acid and heperine. Hyaluronic acid. So if you will look at the structure it has it is a heteropolyaccharide because there are two monomer components. So the structure contains alternating residues of the n acetyl beta dlucosamine and dlucinate. Highly viscous hyaluronic acid solutions serves as lubricants in the fluid of joints in our body and they're also associated with a jelly like cons consistency of the vitrius humor of the eye. So hyaluronic acid have a glassike appearance. Dlucorinate is a caroxilate ion formed when dlucaronic acid loses its hydrogen atom. So hyaluronic acid can be found in our eyes, in our skin and in our joints. So today hyaluronic acid is very famous for being a component of cosmetic products. Last we have heperine. Heperine is a small highly sulfated polysaccharide with only 15 to 90 disaccharide residues per chain. So its repeating unit contains dlucclorinate 2 sulfate and n sulfo dlucosamine 6 sulfate. Heperine is known to be a blood anti-coagulant. So it's naturally present in mast cells and released at the sight of injury. So mast cells are part of the body's immune system. They play an important role in the healing of wounds and the defense of our body against pathogens. They are more abundant in tissues that commonly come into contact with the outside world. It prevents the formation of clots in the blood and retards the growth of existing clots within the blood. However, it does not break down clots that have already been formed.