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Exam 17: Carbohydrates

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Question 1

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Maltose is a disaccharide formed from two units of D-Glucose. The production of maltose from germinating cereal grains (such as barley) is called malting, which is the first step of the brewing process. During germination, the concentration of amylases, which are the enzymes producing maltose from starch, is maximal. Maltose is then consumed by yeast, which produces ethanol and carbon dioxide. What type of glycosidic bond can you discern?

A) " $\beta$ -1,4 glycosidic bond"
B) " $\alpha$ -1,4 glycosidic bond"
C) " $\beta$ -1,2 glycosidic bond"
D) " $\alpha$ -1,2 glycosidic bond"

E) A) and B)
F) None of the above

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Question 2

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The structure of D-Gluconic acid is,

A) True
B) False

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Question 3

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Glucose, Galactose, and Fructose are aldohexoses.

Glycogen is a branched component of starch.

Lactose, which makes up between 2 to 8 percent of milk (depending on the species) is a disaccharide, in which D-Galactose and D-Glucose are linked. What type of glycosidic bond can you discern?

Which sugars and classifications are correctly matched? I. D-Glucose and aldohexose II. D-Galactose and aldopentose III. D-Ribose and ketopentose IV. D-Fructose and ketohexose V. D-Mannose and ketohexose

Sucrose is an acetal.

D-Glucosamine, D-Mannosamine, and D-Galactosamine are C-2 stereoisomers of each other.

Which of the labeled bonds is a glycosidic bond?

How many carbon atoms in an aldohexose are NOT stereocenters?

Assign the stereocenters in D-Galactose according to the S/R-system.

Amylose and amylopectin are unbranched components of starch.

Which are disaccharides? I. sucrose II. glucose III. maltose IV. lactose V. galactose

How many stereoisomers are there in a 2-ketohexose?

Draw the structure of D-Sorbitol from the information given.

What is the relationship between the following compounds?

$\beta$ -D-Glucopyranose ( $\beta$ -D-Glucose) and dissolved oxygen are converted by the enzyme glucose oxidase into D-Gluconic acid, and an inorganic byproduct. This reaction is used to measure the glucose-content in blood. What is the inorganic byproduct?

How many stereocenters are there in a 2-ketohexose?

2,3,4,6-Di-O-isopropyliden-sorbofuranose undergoes oxidation at a platinum-catalyst and subsequent hydrolysis to 2-Keto-L-gulonic acid. Complete the reaction scheme.

L-Sorbofuranose reacts with two molecules of acetone. Complete the reaction scheme.