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Example Questions
Example Question #41 : Identifying Biochemical Molecules
Identify the aldose pictured, including its alpha or beta designation.
-D-ribose
-D-mannose
-D-glucose
-D-glucose
-D-mannose
-D-mannose
The structure pictured is mannose because the hydroxyl groups at carbons 2, 3, and 4 are situated cis, cis, and trans (respectively) to the attached to carbon 5.
The mannose pictured is in alpha form because the hydroxyl group at carbon 1 is trans to the attached to carbon 5.
Example Question #2 : Help With Organic Carbohydrates
The Fischer projection pictured is a form of glucose. The carbon labeled "x" is the chiral carbon farthest away from carbon 1 and the hydroxyl group connected to carbon "x" is on the right. This fact designates that the glucose as what configuration?
L
Beta
D
Pyranose
Alpha
D
The chiral carbon farthest away from carbon 1 is designated as "D" if its hydroxyl group is on the right side in the Fischer projection. In other words, this is D-glucose because the hyroxyl group on carbon "x" is oriented to the right.
Example Question #42 : Identifying Biochemical Molecules
What is the name of the aldose pictured in this Fischer projection?
L-fructose
D-arabinose
L-xylose
D-ribose
L-lyxose
D-ribose
The structure is D-ribose because it is a five-carbon aldose with the hydroxyl groups on carbons 2, 3, and 4 all on the right in the Fischer projection.
Example Question #41 : Identifying Monomers And Dimers
Which of the following is not a monosaccharide?
Galactose
Lactose
All of these are monosaccharides
Fructose
Glucose
Lactose
While glucose, galactose, and fructose are all monosaccharides, lactose is a disaccharide comprised of two monosaccharides, glucose and galactose, joined by a -1,4-glycosidic bond.
Example Question #42 : Identifying Monomers And Dimers
L-Glucose is found as 2 different hexose stereoisomers in solution: and glucose.
Suppose both and L-glucose were polymerized into long glycosidic linkages. Which of the two polymers could be catabolized (broken down into component parts) by a human?
-L-glucose
Neither stereoisomer
Both stereoisomers
-L-glucose
Neither stereoisomer
In nature, L-sugars are indigestible by humans. In the case of L-glucose, even though our bodies can break down polymers of -D-glucose, it cannot digest L-glucose.
Example Question #15 : Identifying Monosaccharides
Which of the following compounds is not a monosaccharide?
Glucose
Galactose
Fructose
Lactose
Ribose
Lactose
Out of all the sugars listed, lactose is the only one that is not a monosaccharide. Lactose is composed of a glucose and galactose bound together in a glycosidic linkage.
Example Question #13 : Identifying Monosaccharides
Which sugar is another name for "blood sugar?"
Lactose
Glucose
Sucrose
Fructose
Glucose
Glucose is also called "blood sugar" because it is the main sugar found in our blood. Sucrose is what we know as "table sugar" because it is commonly found in our kitchens and used in baking etc. Fructose is also known as "fruit sugar" because it occurs in naturally-occurring fruits, giving them their sweetness. Lactose is sometimes called "milk sugar" because it is found in milk.
Example Question #1 : Identifying Disaccharides
Which of the following is not a disaccharide?
All of these are disaccharides
Sucrose
Maltose
Lactose
Cellobiose
All of these are disaccharides
Review the specific types of monosaccharides and glycosidic bonds that are involved in these disaccharides. Remember that disaccharides are formed upon dehydration synthesis of two monosaccharides.
Maltose is composed of two glucose monomers with an 1-4 linkage.
Cellobiose is composed of two glucose monomers with a 1-4 linkage.
Sucrose is composed of one glucose monomer and one fructose monomer with an 1-2 linkage.
Lactose is composed of one galactose monomer and one glucose monomer with a 1-4 linkage.
Example Question #1 : Identifying Disaccharides
Maltose is a disaccharide composed of which two monosaccharides?
Galactose + galactose
Glucose + fructose
Glucose + glucose
Fructose + fructose
Glucose + galactose
Glucose + glucose
Maltose, which is made up of two glucose monomers joined by an alpha-1,4 linkage, is the correct answer. On the other hand, lactose is made up of one glucose monomer and one galactose monomer, and sucrose is made up of one glucose monomer and one fructose monomer.
Example Question #2 : Identifying Disaccharides
Which of the following substances are found in fructose?
Galactose
None of these are found in fructose
Lactose
Glucose
None of these are found in fructose
Fructose is a monosaccharide; therefore, it is only made up of one type of carbohydrate. Disaccharides are made up of two types of monosaccharides. For example, lactose is made up of galactose and glucose whereas sucrose is made up of glucose and fructose. Polysaccharides are made up of multiple units of monosaccaharides.