The main function of carbohydrates is to provide energy for your body, and support muscle activities, brain activity, breathing, and other important functions. Carbohydrates consist of sugars known as saccharides. Most carbohydrate foods contain many interconnected saccharides known as polysaccharides. Digestion of carbohydrates begins in the mouth and ends when polysaccharides are broken down into individual sugars or monosaccharides that can be absorbed by the body.
Figure 1: Laboratory demonstration showing patient reception for this class. The intestinal glucose transport simulation is provided by Labster and available for University / College classes.
The small intestine then produces enzymes called lactase, sucrase, and maltase, which break down disaccharides into monosaccharides which are then absorbed in the small intestine. The small intestine consists of the duodenum, jejunum, and ileum. The intestinal epithelium is specialized and like other epithelia, these cells have different structures and proteins on the mucosal side, which is bath by solutions in the intestinal lumen (where food is located), and the serosal side, which is immersed in the extracellular fluid which communicates with the bloodstream.
Figure 2: Anatomy and structure of the small intestine
We've put together various resources to help teachers discuss this topic interestingly and practically. Read on to discover more ways to make it easier for your students to understand everything they need to know about intestinal glucose transport. We try to show all the problems that students face when dealing with the topic. We have also listed some practical solutions to become successful. Finally, we share why virtual lab simulations are beneficial not only for your students but also for you as an educator to convey concepts more effectively.
There are three reasons why students feel challenged by the topic of intestinal glucose transport. Recognizing this problem is the first step in making the topic more convenient to understand.
Students learn that carbohydrates must be broken down into glucose before the body can use them as a source of energy, but knowledge of how the body absorbs them is not clearly explained. Students find it hard to believe because they cannot observe these phenomena in real life.
The intraluminal pH changes rapidly from very acidic in the stomach to around pH 6 in the duodenum. It gradually increases in the small intestine from pH 6 to about pH 7.4 in the terminal ileum. The pH drops to 5.7 in the cecum but gradually rises again, reaching a pH of 6.7 in the rectum. However, rectal pH can vary with diet.
The everted intestinal sacs can be used to study glucose transport across the intestinal epithelium. The intestines are tilted to ensure all the contents are removed so as not to interfere with the results. You can see the basic steps below:
Figure 3: Intestine everted pouch preparation
There are three main approaches to measuring glucose concentration:
condensation methods, and
Enzyme method: The glucose test reagent contains glucose oxidase, peroxidase, and o-dianisidin. Oxidase reacts with glucose to produce gluconic acid and hydrogen peroxide. Peroxidase reacts with hydrogen peroxide formed during the oxidation of glucose and colorless reduced o-dianicidin to form a brown product (oxidized o-dianisidin).
Since this product is unstable, sulfuric acid is added to stop the reaction by denaturing all enzymes and a pink product (protonated oxidized dianisidine) is formed, which is stable and absorbs light at 540 nm. For each molecule of glucose in the solution, one molecule of this colored product is formed.
Figure 4: Glucose test reactions
To overcome blockages encountered while teaching intestinal glucose transport, educators can use the following solutions in their classrooms. They can not only make teaching easier for teachers like you but can also make lessons clearer and easier for your students to understand.
Make a dilution of the solution. The diagram in Figure 1 shows the required volume.
Figure 5: glucose dilution
The molecular weight of glucose is 180 grams/mol. So to make 100 mL of a 50 mmol/L glucose solution, you first need to find out how many grams of glucose are needed. Applying this equation
m = n.V.C,
where m is the mass in g
n is the number of moles
V is the volume in L
C is the concentration in moles/L
m = 180 g/mol•0.1 liter•0.05 mol/L, which means we need 0.9 grams of glucose to make a stock solution.
Then, to make 25, 10, 5, and 1 mmol/L dilutions, we can use the following equation to calculate how much distilled water and 50 mmol/L glucose we need to add to make 5 mL of each target dilution:
V1 C1 = V2 C2
V1 = V2•C2 / C1 where
V1 and C1 are the volume and concentration of the solution to be diluted, and V2 and C2 are the volume and concentration of the solution obtained by mixing V1 with water to the desired volume (or sometimes another solvent).
There are also dilution series that are slightly different because the concentration ratio between solutions is usually constant and subsequent solutions are prepared by diluting the previous solution 1:10, 1:100, and so on. One application of this dilution, serial or otherwise, is curve calibration. If the analysis is carried out simultaneously for the desired sample and a glucose standard of known concentration, a calibration curve can be obtained and an equation can be used to determine the unknown concentration when the absorbance is known.
Intestinal epithelial cells form the interface between the intestinal lumen (mucosal side) and blood (serosal side) and have many different receptors and channels that allow the flow of different molecules in both directions.
Passive transport or active transport are the two channels of transport. Passive transport occurs independently as a function of concentration: molecules move from a more concentrated solution to a less concentrated solution until equilibrium is reached. Active transport takes place against the gradient and requires energy. Some transport only one type of molecule and others can transport more than one. A popular method for studying glucose transport is the use of blockers. One of these inhibitors, ouabain, can block sodium-potassium ATPase.
Intestinal glucose cotransporter, SGLT1
Transporters are not only affected by blockers. Sometimes genetic mutations also play a role. For example, decreased or impaired mucosal glucose and sodium symptoms will lead to their accumulation in the intestinal lumen and water retention. In turn, due to dehydration, plasma volume may decrease, causing an increase in sodium concentration.
The realization that glucose is absorbed by co-transport with sodium was an important scientific discovery that led to treatments that saved many lives. One of the main killers of young children is diarrhea, which is often caused by infections such as cholera. For example, in 1982 the World Health Organization estimated that there were more than one billion cases of diarrhea-causing nearly five million child deaths. Death from diarrhea can occur when a person loses so much fluid that their plasma volume becomes very low, causing an increase in blood potassium (possibly depolarizing cells) and possibly causing blood pressure to become so low that the heart cannot pump blood through the body effectively.
In 2013, there were more than 1.7 billion cases of diarrhea and the number of diarrhea-related deaths in children was reduced to less than 800,000 thanks to the introduction of oral rehydration therapy (ORT). The commonly used ORT solutions are 45 mmol/L NaCl, 75 mmol/L glucose, 20 mmol/L KCl, and 10 mmol/L trisodium citrate.
A disease first identified nearly 30 years ago, is characterized by the onset of severe watery diarrhea in newborns, leading to death if glucose and galactose are not removed from the diet. Immediate improvement was observed when the patient took artificial milk without glucose, galactose and lactose. This shows a defect in the Na+/glucose cotransporter brush border can have serious health implications It was concluded that each child experienced glucose-galactose malabsorption and subsequently managed to maintain a glucose/galactose-free diet.
A unique way to teach intestinal glucose transport is through virtual laboratory simulations. At Labster, we are dedicated to providing fully interactive state-of-the-art lab simulations that use gamified elements such as storytelling and scoring systems in an immersive, 3D world.
Check out Labster's intestinal glucose transport simulation, which empowers students to learn through inquiry-based active learning. In the simulation, students embark on a mission to help care for a baby suffering from diarrhea and not gaining weight. He also had elevated levels of sodium in the blood and glucose in the stool and urine.
Learn more about intestinal glucose transport simulations here or contact us to find out how you can start using our virtual labs with your students.
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