Monosaccharides Glucose galactose and fructose are the most important monosaccharides Learning Goal Identify and draw the d or l configurations of the Fischer projections for common monosaccharides ID: 1048687
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1. 15.2 Fischer Projections of MonosaccharidesGlucose, galactose, and fructose are the most important monosaccharides. Learning Goal Identify and draw the d or l configurations of the Fischer projections for common monosaccharides.
2. Fischer ProjectionsA Fischer projection, used to represent carbohydrates,places the aldehyde group (most oxidized) at the top.shows the — H and — OH groups on the horizontal intersecting line.places the achiral — CH2OH group at the bottom.
3. d and l NotationsIn a Fischer projection, the — OH group on thechiral carbon farthest from the carbonyl group determines an l or d isomer.left is assigned the letter l.right is assigned the letter d.Core Chemistry Skill Identifying d- and l-FischerProjections
4. d and l Isomers: Monosaccharides
5. Important Monosaccharidesd-Glucose, d-galactose, and d-fructose are the most important monosaccharides. They are all hexoses with the molecular formula C6H12O6 and are isomers of each other.
6. Monosaccharides: d-Glucosed-Glucoseis the most common hexose.is found in fruits, vegetables, corn syrup, and honey.is also known as dextrose and blood sugar in the body.is a building block of the disaccharides sucrose and lactose and of polysaccharides such as cellulose and glycogen.
7. Monosaccharides: d-Galactosed-galactose, an aldohexose with the formula C6H12O6,is obtained from the disaccharide lactose, found in milk.is important in the cellular membranes of the brain and nervous system.In a condition called galactosemia, the enzyme needed to convert d-galactose to d-glucose is missing.galactose accumulates in the blood and tissue, which can lead to cataracts, mental retardation, failure to thrive, and liver disease.
8. Monosaccharides: d-Fructosed-Fructoseis a ketohexose with the formula C6H12O6.is the sweetest of the carbohydrates, twice as sweet as sucrose (table sugar).is obtained as one of the hydrolysis products of sucrose.High-fructose corn syrup (HFCS) is a sweetener that is produced by using an enzyme to break downsucrose to glucose and fructose.
9. Guide to Identifying d- or l- Monosaccharides
10. Study CheckIdentify the following structure of a monosaccharide as d- or l-ribulose.
11. SolutionIdentify the following structure of a monosaccharide as d- or l-ribulose.STEP 1 Number the carbon chain starting at the top of the Fischer projection.ANALYZE Given NeedTHE ribulose identify as D- or L- PROBLEM Fischer projection
12. Study CheckIdentify the following structure of a monosaccharide as d- or l-ribulose.STEP 2 Locate the chiral carbon farthestfrom the top of the Fischerprojection. STEP 3 Identify the position of the — OH group as d- or l-. The — OH group is drawn on the right of carbon 4, making it d-ribulose.
13. Chemistry Link to Health:Hyperglycemia and HypoglycemiaIn the body, glucose has a normal blood level of 70–90 mg/dL.a glucose tolerance test measures blood glucose for several hours after ingesting glucose.
14. Chemistry Link to Health:Hyperglycemia and HypoglycemiaDiabetes mellitus can cause hyperglycemia, whichoccurs when the pancreas is unable to produce sufficient quantities of insulin.allows glucose levels in the body fluids to rise as high as 350 mg/dL of plasma.Symptoms of diabetes include thirst and excessive urination.increased appetite and weight loss.In older adults, diabetes is sometimes a consequence of excessive weight gain.
15. Chemistry Link to Health:Hyperglycemia and HypoglycemiaWhen a person is hypoglycemic, the blood glucose level rises and then decreases rapidly to levels as low as 40 mg/dL.low blood sugar may occur as a result of an overproduction of insulin by the pancreas.symptoms may appear, such as dizziness, general weakness, and muscle tremors.a diet may be prescribed that consists of several small meals high in protein and low in carbohydrates.
16. Chemistry Link to Health:Glucose TestingNormally, blood glucose flows through the kidneys and is reabsorbed into the bloodstream. When the blood level exceeds about 160 mg of glucose/dL of blood, the kidneys cannot reabsorb all of the glucose, and it spills over into the urine, a condition known as glucosuria.The color of the dye o-methylaniline on a test strip determines the glucose level in urine.
17. Chemistry Link to Health:Glucose TestingA symptom of diabetes mellitus is a high level of glucose in the urine, which can be identified using Benedict’s test.
18. Study CheckIn the following Fischer projection, identify the monosaccharide as a d or an l isomer.
19. SolutionIn the following Fischer projection, identify the monosaccharide as a d or an l isomer.— OH is on the left;it is an L isomer.