Chapter 11, Sugars and Polysaccharides Video Solutions, Biochemistry

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Problem 1

The trisaccharide drawn below is named raffinose. What is its systematic name? Is it a reducing sugar?

Emily Himsel

Numerade Educator

02:12

The systematic name of melezitose is $O$ -a-D-glucopyranosyl$(1 \rightarrow 3)-O-\beta-D-$ fructofuranosyl- $(2 \rightarrow 1)-\alpha-D-$ glucopyranoside Draw its molecular formula. Is it a reducing sugar?

Lijeesh Krishnan

Numerade Educator

03:05

Problem 3

Name the linear form of D-glucose using the $(R S)$ chirality nomenclature system. [See Section 4-2C. Hint: The branch toward C1 has higher priority than the branch toward C6.]

George Bennett

Numerade Educator

01:31

Problem 4

Draw the $\alpha$ -furanose form of $\mathrm{D}$ -talose and the $\beta$ -pyranose form of L-sorbose.

Freddie Montague

Numerade Educator

01:36

Problem 5

The $\mathrm{NaBH}_{4}$ reduction product of $\mathrm{D}$ -glucose may be named L-sorbitol or D-glucitol. Explain.

George Bennett

Numerade Educator

01:58

Problem 6

How many different disaccharides of D-glucopyranose are possible? How many trisaccharides?

Khalida Dawar

Numerade Educator

04:55

Problem 7

A molecule of amylopectin consists of 1000 glucose residues and is branched every 25 residues. How many reducing ends does it have?

Jennifer Stoner

Numerade Educator

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Problem 8

Most paper is made by removing the lignin from wood pulp and forming the resulting mass of largely unoriented cellulose fibers into a sheet. Untreated paper loses most of its strength when wet with water but maintains its strength when wet with oil. Explain.

Emily Himsel

Numerade Educator

03:59

Problem 9

Write a chemical mechanism for the acid-catalyzed mutarotation of glucose.

Khalida Dawar

Numerade Educator

05:57

Problem 10

The values of the specific rotation, $[\alpha]_{\mathrm{D}}^{20},$ for the $\alpha$ and $\beta$ anomers of $\mathrm{D}$ -galactose are $150.7^{\circ}$ and $52.8^{\circ},$ respectively. A mixture that is $20 \% \alpha$ -D-galactose and $80 \%$ \beta-D-galactose is dissolved in water at $20^{\circ} \mathrm{C}$. What is its initial specific rotation? After several hours, the specific rotation of this mixture reached an equilibrium value of $80.2^{\circ} .$ What is its anomeric composition?

George Bennett

Numerade Educator

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Problem 11

Name the epimers of D-gulose.

Emily Himsel

Numerade Educator

04:09

Problem 12

Exhaustive methylation of a trisaccharide followed by acid hydrolysis yields equimolar quantities of $2,3,4,6-$ tetra- $O$ methyl-D-galactose, 2,3,4 -tri-O-methyl-D-mannose, and $2,4,6-$ tri- $O$ -methyl-D-glucose. Treatment of the trisaccharide with $\beta-$ galactosidase yields D-galactose and a disaccharide. Treatment of this disaccharide with $\alpha$ -mannosidase yields D-mannose and D-glucose. Draw the structure of the trisaccharide and state its systematic name.

Ly Tran

Numerade Educator

01:34

Problem 13

The enzyme $\beta$ -amylase cleaves successive maltose units from the nonreducing end of $\alpha(1 \rightarrow 4)$ glucans. It will not cleave at glucose residues that have an $\alpha(1 \rightarrow 6)$ bond. The end products of the exhaustive digestion of amylopectin by $\beta$ -amylase are known as limit dextrins. Draw a schematic diagram of an amylopectin molecule and indicate what part(s) of it constitutes limit dextrins.

Rashmi Sinha

Numerade Educator

04:16

Problem 14

One demonstration of P.T. Barnum's maxim that there's a sucker born every minute is that new "reducing aids" regularly appear on the market. An eat-all-you-want nostrum, which was touted as a "starch blocker" [and which the Food and Drug Administration (FDA) eventually banned], contained an $\alpha$ -amylase-inhibiting protein extracted from beans If this substance had really worked as advertised, which it did not, what unpleasant side effects would have resulted from its ingestion with a starch-containing meal? Discuss why this substance, which inhibits $\alpha$ -amylase in vitro, would not do so in the intestines after oral ingestion.

Nick Johnson

Numerade Educator

02:26

Problem 15

Treatment of a 6.0 -g sample of glycogen with Tollens' reagent followed by exhaustive methylation and then hydrolysis yields $3.1 \mathrm{mmol}$ of $2,3-\mathrm{di}-\mathrm{O}$ -methylglucose and $0.0031 \mathrm{mmol}$ of 1,2,3 -tri- $O$ -methylgluconic acid as well as other products. (a) What fraction of glucose residues occur at $(1 \rightarrow 6)$ branch points, and what is the average number of glucose residues per branch? (b) What are the other products of the methylation-hydrolysis treatment and in what amounts are they formed?
(c) What is the average molecular mass of the glycogen?

Rashmi Sinha

Numerade Educator

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Problem 16

The lysis of a culture of $E$. coli yields a solution with $\mathrm{mu}$ cuslike viscosity. Adding DNase to the solution greatly reduces this viscosity. What is the physical basis of the viscosity?

Emily Himsel

Numerade Educator

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Problem 17

Instilling methyl-c-D-mannuside into the bladder of a mouse prevents the colonization of its urinary tract by $E$ coli. What is the reason for this effect?

Emily Himsel

Numerade Educator

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