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Biochemistry- Carbohydrate Structure and Function
Terms in this set (16)
Sucrose is a disaccharide formed via a glycosidic bond between glucose (C-1) and fructose (C-2). What functional group is created as a result of this new linkage?
A. An ether
B. A ketone
C. A lactone
D. A lactam
We know that the C-1 of glucose and the C-2 of fructose both have hydroxyl groups. We also know that when these functional groups condense, water is lost. This creates a glycosidic bond in a form of a C-O-C bond sequence, which makes it an ether.
D-Glucose and D-mannose are epimers of each other, meaning that these sugars are examples of:
C. meso compounds
D. constitutional isomers
Epimers are a subtype of diastereomers that differ at exactly one chiral carbon. Diastereomers are non superimposable configurations of (meaning they can not be placed on top of each other and be the same image) molecules with similar connectivity. They differ at at least one- but not all- chiral carbons.
(see picture #21 and 22)
Contrast the connection defined by the box labeled 1 and the connection defined by the box labeled 2.
A. Box 1 represents the connection a 1,3- alpha linkage while Box 2 represents a 1,3-beta linkage.
B. Box 1 represents a 1,3- beta linkage while Box 3 represents a 1,3-alpha linkage.
C. Box 1 and Box 2 both represent 1,3-alpha linkages.
D. Box 1 and Box 2 both represent 1,3-beta linkage.
The anomeric carbon in sugars are labeled as alpha or beta. If they have opposite stereochemistry- axial (up and down) and equatorial (slanted)- the compound is alpha; if they have the same stereochemisty then the compound is beta.
(see picture #21 and 22)
The branched connection defined by the box labeled three is most analogous to a structure in which of the following compounds?
Oligopeptides do not contain sugars and are not branched and Glycogen is the only choice that is branched.
(See picture #23)
Given the Fischer projection of D-fructose above, what is the correct IUPAC name for D-fructose?
A. (3S, 4R, 5R)-1,3,4,5,6-pentahydroxyhexan-2-one
B. (3R, 4S, 5S)- 1,3,4,5,6-pentahydroxyhexan-2-one
C. (3R, 4S, 5R)- 1,3,4,5,6-pentahydroxyhexan-2-one
(see picture #24 for R vs S confirmation) (all D sugars are R because the last chiral center has the OH is on the right side)(most sugars have the stereo center as a R (bc most are D) while most amino acids are S) By numbering the highest priority we find that C-3 is a S configuration and C-4 and C-5 are both R configurations.
A new drug to treat high blood pressure has recently completed mammalian trials. In a study test for safety and efficacy in humans, one group receives the new drug and another receives a sugar pill. Then the assessor measures behavioral outcomes as a result of treatment in both group. which of the following would reduce experimental bias?
1. withholding the identity of the treatment from the patients
2. Withholding knowledge of group membership of each patient from the research assistant analyzing the data
3. Withholding knowledge of group membership of each patient from the assessor
A. 1 only
B. 1 and 3
C. 2 and 3
D. 1, 2, 3
Blindedness enhances studies by removing any influence that might occur when the identity of the given intervention is known compared to placebo. It is appropriate to blind both research personnel and the participants to the information.
alpha-D-glucopyranose and beta-D-glucopyranose are exampled of:
A. 1 and 2
D. 2 and 3
Epimers- Monosaccharide diastereomers that differ in their configurations about only one carbon
Anomers- A subtype of epimers that differ at the anomeric carbon. The anomeric carbon is the new chiral center formed in ring closure.
Enantiomers- Have equal but opposite optical activities.
Alpha is trans
Beta is cis
Which of these complex carbohydrates contains a Beta-glycosidic linkage?
These are the known structure of these sugars:
Sucrose- the disaccharide glucose-alpha-1,2-fructose
Cellulose- a chain of Beta-D-glucose molecules liked by Beta-1,4 glycosidic bonds
Maltose- Disaccharide glucose-alpha-1,4-glucose
Amylose-Glucose polymer linked via alpha-1,4 glycosidic bonds
A biochemist purifies a compound from the roots of a newly discovered species of plant. Analysis reveals that the compound is made only of glucose subunits connected via alpha-1,4 and alpha-1,6 glycosidic linkages. This compound is most similar to which of the following polysaccharides?
Amylopectin - Made of glucose subunits connected by alpha-1,4 with occasional Alpha-1,6 for branching
Amylose- Made of only alpha-1,4 linked glucose subunits
Cellulose- Made of only Beta-1,4 linked glucose subunits
Pectin- Made of galactose subunits and not glucose subunits
Which of the following statements about D-carbohydrates is true?
A. All D-carbohydrates rotate plane polarized light in a clockwise direction
B. All D-sugars also have an (S) configuration
C. The chiral center farthest from the carbonyl carbon determines its destination as D
D. D - carbohydrates are rarely found in biologically active systems
A is not true since direction of rotation must be determined experimentally for other carbohydrates. B is also false because the configuration can be either S or R configuration. C is true since nomenclature rules dictate that the stereochemistry of the carbohydrate is determined by the highest numbered asymmetric carbon. D is also false because nearly all naturally occurring carbohydrates are found in the D configuration.
Lactase persistence a relatively recent revolutionary phenomenon that has enabled humans to digest lactose in adulthood. This mutation allowed humans to be able to digest lactose into:
A. glucose and galactose
B. glucose and sucrose
C. Sucrose and fructose
D. sucrose and galactose
A student adds iodine to a sample of bacterial cell membrane in order to determine the presence of sugars. The sample does not test positive. Can the student reasonably assume that the sample does not contain any sugars?
A. yes, because iodine should intercalate between the helical structures of starches.
B. no, because iodine only test for long heteropolysaccharides that may not be present in the sample.
C. No, because insoluble sugars, such as cellulose, do not form helix complexes with iodine
D. no, because proteoglycans found in bacterial membranes Banh to iodine
Iodine is a reagent that test for the presence of starch and does so by sitting inside the helix confirmation amylose typically makes, forming a starch iodine complex; thus, iodine is able to determine the presence of starch but not all sugars
Which Adams are involved in the crystallization of fructose to its pyranose form?
A. carbon two and the hydroxyl group on carbon six
B. carbon one in the hydroxyl group on carbon six
C. Carbon one in the hydroxyl group and carbon five
D. Carbon two in the hydroxyl group on Carbon five
We know that fructose is a ketohexose, a six carbon molecule with the ketone functional group. As a result the crystallization process cannot involve C- 1 as this would require the presence of aldehyde functional group. Instead crystallization of fructose requires the reaction between the hydroxyl group on C-6 and the ketone carbon C-2.
Which of the following sugars contain Beta glycosidic linkages?
A. one only
B. 2, 3 and four only
C. Two, three, and five only
D. One and four only
B-glycosidic linkages are formed between two monosaccharides (or a carbohydrate chain and a monosaccharide) when the hydroxyl group used to attach the next monosaccharide to the parent carbohydrate chain it is the Beta position.
Cellulose is comprised of B-1, 4 linkages am lactose is also known as galactose-B-1,4-glucose
A biologist clone a a bacterium able to produce both alpha-amylase and beta-amylase and mutates a colony by creating a genetic lesion at the site of the amylase genes. He fines that the mutated colony is unable to fully digest amylopectin but can still digest amylose. These results support which of the following conclusions about this experiment?
A. The alpha- amylase gene was mutated.
B. The beta-amylase gene was mutated
C. The genetic lesion did not inhibit the transcription of alpha-amylase or beta-amylase
D. Both the alpha-amylase and beta-amylase genes were mutated
Starches such as amylose and amylopectin are broken down by enzymes in the body and are used as a source of energy. Amylose is degraded by alpha and beta amylase. Beta cleaves amylose at the nonreducing end of the polymer (end with acetal) to yield maltose, while alpha cleaves randomly along the chain to yield shorter polysaccharide chains, maltose and glucose. Because amylopectin is highly branched, deb ranching enzymes help degraded the chain.
The question tells us that amylopectin can't be digested, but amylose can. This means that Beta-amylase is intact. However, alpha-amylase is likely mutated because if it were functional, it would be able to break down some of amylopectin's branches.
Which of the following molecules are epimers of D-glucose?
(See picture #85, 86, 87)
A. 1, 2, 3
B. 1 and 3
C. 2 and 4
2 is glucose itself, 4 differs from glucose by the chirality at two carbons and this is a diastereogmer but not an epimer; 1 and 3 both differ chirality at one carbon each and are epimers of glucose
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