AP Biology Chapter 5.2

16. What is a glycosidic linkage?

A glycoside linkage is a covalent bond formed between two monosaccharides by a dehydration reaction.

Most monosaccharides are some multiple of (CH2O). For example, ribose is a 5-carbon sugar with the formula C5H10O5. It is a pentose sugar. (From the root penta-, meaning 5.) What is the formula of a hexose sugar?

C6H12O6

12. Here are the three hexose sugars. Label each of them. Notice that all sugars have the same two functional groups. Name them: a. C=O ___________________ b. —OH ___________________

Carbonyl group Hydroxyl group

13. What is the difference between an aldehyde sugar and a ketone sugar?

Depending on the location of the carbonyl group, a sugar is either an aldose (aldehyde sugar) or a ketose (ketone sugar). In aldehyde sugars, the carbonyl group is at the end of the carbon skeleton, while in the ketone sugars, the carbonyl group is within the carbon skeleton.

Why can you not digest cellulose? What organisms can?

Humans cannot digest cellulose because they lack the enzyme that can hydrolyze its beta linkages. Humans do posses enzymes that digest starch by hydrolyzing its alpha linkages; however, these enzymes cannot hydrolyze the beta linkages of cellulose because of the distinctly different shapes of these two molecules.

12. So, as a quick review, all of the sugars in the figure above have the same chemical formula: C6H12O6. What term did you learn in Chapter 3 for compounds that have the same molecular formulas but different structural formulas?

Isomers

Let's look at carbohydrates, which include sugars and starches. First, what are the monomers of all carbohydrates?

Monosaccharides, or simple sugars

There are two categories of polysaccharides. Name them and give examples

Storage- starch glycogen Structural-cellulose chitin

18. Hereisamoleculeofstarch,whichshows1-4glycosidiclinkages.Translateandexplainthis terminology in terms of carbon numbering.

When glucose forms a ring, the hydroxyl group attached to the number 1 carbon is positioned either below or above the plane of the ring. These two ring forms for glucose are called alpha and beta. In starch, all the glucose monomers are in the alpha configuration.

Here is a molecule of starch, which shows 1-4 glycosidic linkages. Translate and explain this terminology in terms of carbon numbering.

When glucose forms a ring, the hydroxyl group attached to the number 1 carbon is positioned either below or above the plane of the ring. These two ring forms for glucose are called alpha and beta. In starch, all the glucose monomers are in the alpha configuration.

20. Let's review some key points about the carbohydrates. Each prompt below describes a unique carbohydrate. Name the correct carbohydrate for each. a. Has 1-4 B glucose linkages b. Is a storage polysaccharide produced by vertebrates; stored in your liver c. Glucose +________ form sucrose d. "Milk sugar" e. Structural polysaccharide that gives cockroaches their crunch f. Malt sugar; used to brew beer g. Structural polysaccharide that comprises plant cell walls

starch Has 1-4 B glucose linkages b. glycogen Is a storage polysaccharide produced by vertebrates; stored in your liver c glucose Two monomers of this form maltose d. fructose Glucose + fructose form sucrose e. fructose Monosaccharide commonly called "fruit sugar" f. lactose "Milk sugar" g. chitin Structural polysaccharide that gives cockroaches their crunch h. maltose Malt sugar; used to brew beer i. cellulose Structural polysaccharide that comprises plant cell walls