Biochemistry : Carbohydrate Structures and Functions
Study concepts, example questions & explanations for Biochemistry
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Example Questions
Example Question #1 : Structural Carbohydrates
Which of the following is not an example of a compound that contains carbohydrate in its structure?
Collagen
Peptidoglycan
Glycogen
Cellulose
Chitin
Collagen
To identify the answer choice that is NOT a polysaccharide, let's go delve into each answer choice a bit.
Cellulose is a polysaccharide and also a very important component of the cell wall of plants. It consists of many glucose sugars bound together via beta (1-4) linkages.
Peptidoglycan is also a polysaccharide and a very important component of the cell wall of bacteria. Its structure consists of alternating N-acetylglucosamine and N-acetylmuramic acid connected via beta (1-4) linkages. Both of these are modified sugar molecules.
Chitin is a polysaccharide that plays an important role in the structure of the exoskeleton of many fungi, arthropods, and insects. Its structure consists of a long chain of N-acetylglucosamine, which is a derivative of the sugar glucose.
Collagen is the only answer choice that does not represent a carbohydrate. Rather, collagen is a protein that plays a very important role in the extracellular matrix of various connective tissues found in animals.
Glycogen is a branched form of glucose that is the storage form in animals. It contains beta (1-4) and beta (1-6) linkages.
Example Question #1 : Structural Carbohydrates
Both cellulose and starch are polymers of glucose; why can't and enzyme that breaks down starch also break down cellulose?
Cellulose is composed of D-glucose molecules while starch is composed of L-glucose molecules
Glucose monomers in starch are double bonded together while they are connected by single bonds in cellulose
Cellulose forms a right handed helix, while starch forms a left handed helix
Cellulose is composed of cyclic glucose molecules while starch is composed of linear glucose molecules
Cellulose and starch are made up of different stereoisomers of glucose
Cellulose and starch are made up of different stereoisomers of glucose
Cyclized monosaccharides can exist in two different stereoisomers that depend on the orientation of the hydroxyl group on the anomeric carbon. If this 
Example Question #2 : Structural Carbohydrates
Which of the following is not a glycosaminoglycan?
Dermatan sulfate
Hyaluronate
Keratan sulfate
Erythropoietin
Heparin
Erythropoietin
A glycosaminoglycan (GAG) is a long, unbranched polysaccharide that consists of many repeating disaccharide units. Dermatan sulfate, keratan sulfate, hyaluronate, and heparin are all examples of glycosaminoglycans. Erythropoietin, however, is a glycoprotein hormone that stimulates production of red blood cells.
Example Question #3 : Structural Carbohydrates
Which of the following is true of the two forms of starch: amylose and amylopectin?
Amylose and amylopectin are composed of different molecular units
Amylose contains alpha 1,6 glycosidic linkages
Amylose is composed of D-glucose units while amylopectin is composed of L-glucose units
Amylopectin is branched while amylose is not
Most of starch is composed of amylose
Amylopectin is branched while amylose is not
Amylose and amylopectin are the two components of starch. Approximately 80% of starch is composed of amylopectin. Both amylose and amylopectin are comprised of glucose units, and both have only D-glucose units. Amylose differs from amylopectin in that amylose is a single unbranched chain, but amylopectin branches. Therefore, amylopectin has both alpha 1,4 glycosidic linkages as well as alpha 1,6 glycosidic linkages.
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