Quiz

QUIZ

1. Which is not considered a polysaccharide but is instead a disaccharide?

a. Cellulose b. Chitin c. Maltose d. Glycogen

Answer: c. Each of these is a polysaccharide made from different connections of glucose to each other with the exception of Maltose, which is also made from glucose but is a disaccharide.

2. Which six-carbon simple carbohydrate forms a five-membered ring?

a. Fructose b. Galactose c. Glucose d. Ribose

Answer: a. Fructose is a six-carbon sugar that is made into a fivemembered ring because of the location of its carbonyl group, which is a ketone and is not an aldehyde. Both galactose and glucose are sixmembered rings and ribose is a five-carbon sugar.

3. The product of a reaction of an aldehyde with an equivalent number of alcohol units is called what?

a. Acetal b. Hemi-acetal c. Ketal d. Ketose

Answer: b. A hemiacetal is a molecule that represents the reaction between an aldehyde and an equivalent number of alcohol molecules. The structure can be complex but is basically RCHOROH.

4. How many oxygen atoms, by definition, are around the anomeric carbon center?

a. Zero b. One c. Two d. Three

Answer: c. The anomeric carbon has, by definition, a bond with two oxygen atoms at the same time.

5. What best describes glucose as a molecule?

a. Pentose b. Aldohexose c. Furanose d. Ketohexose

Answer: b. Glucose can be named many things. It is a hexose sugar, an aldohexose, an aldose, and a pyranose. It is not a pentose because it has six carbon molecules; it is not a ketohexose because it does not have a ketone group; it is not a furanose because it is a pyranose, a cyclic six-membered ring.

6. What type of sugar cannot possibly be a reducing sugar, being unable to reduce the copper molecule?

a. Hemiacetal b. Ketose c. Acetal d. Aldose

Answer: c. The sugar that becomes or is a reducing sugar must be able to be an aldehyde in its open form. This means that it can be a hemiacetal and, because of tautomerization, it can be a ketose sugar but it cannot be an acetal because it cannot be oxidized into anything.

7. In the glucose or hexose molecule, where does mutarotation occur?

a. At the carbon that has a hydroxyl group b. At the terminal carbon atom c. At the hydroxyl group d. At the anomeric carbon atom

Answer: d. Mutarotation refers to the change between the alpha and beta forms that occurs through the carbonyl intermediate. The carbonyl carbon is the same thing as the anomeric carbon atom.

8. What form is different from the rest when it comes to stereochemistry of sugars?

a. L form b. Plus form c. S form d. Minus form

Answer: b. These are confusing ways of describing sugars. The forms most commonly used are L and D. The L form has the OH side chain on the left of the molecule when written in Fischer form. L, minus, and S are the same thing but the “plus form” is the D or R form.

9. What is the substrate used to alkylate the hydroxyl groups on a carbohydrate in carbohydrate chemistry?

a. An alkyl hydride b. Another alcohol c. An aldehyde d. An ether

Answer: a. An alkyl hydride under basic conditions can cover each of the hydroxyl groups with an alkyl group, effectively blocking these groups from further reactivity, forming multiple ethers with the same side chain.

10. In the acyl addition reaction to carbohydrates, what type of product is formed?

a. Aldehyde b. Ester c. Ether d. Ketone

Answer: b. These will use acid anhydride or acyl halides to add the acyl group onto the alcohol, leading to multiple esters on the hydroxyl side chain.