BIO 322 - Reading Assignment: Carbohydrates

which of the following statements correctly describe the reaction of ketoses with benedicts reagent?

*an ene-diol reaction occurs in solution *ketoses react with Benedict's reagent to give carboxylic acids overall *the CH2OH group adjacent to the carbonyl group undergoes rearrangement to an aldose under basic reaction conditions

which of the following statements about carbohydrates are correct?

*glucose is the main energy source of the brain and nervous system *Complex carbohydrates are nutritionally better for us than simple sugars *Complex carbohydrates such as cellulose also provide dietary fiber

which of the statements describe the sugar ribose?

*ribose is a biologically important molecule found in RNA *ribose is an aldose

Which of the following statements correctly describe an anomeric carbon?

*the anomeric carbon s a chiral center formed when a monosaccharide forms an intramolecular hemiacetal *two anomers may be formed when an intramolecular cyclization takes place to give a hemiacetal

which of the following statements correctly describe a Haworth projection

*the oxygen atom of the hemiacetal is placed in the upper right corner of the hexagon *the first carbon clockwise from the oxygen atom is the anomeric carbon *groups that are on the left side of the original Fischer Projection will be drawn up, above the plane of the ring in a Haworth projection

A compound with three chiral centers have a maximum of _____ different stereochemical configurations.

8

Insulin

A hormone that stimulates the cellular uptake of excess glucose in the body

glucagon

A hormone that stimulates the liver to release glucose into the bloodstream when levels are low.

Heteropolysaccharide

A long-chain polymer consisting of multiple types of monosaccharides, including amino sugars.

Glucose

A monosaccharide broken down in glycolysis to release energy for body functions.

polysaccharide

A polymer containing several monosaccharide units linked together.

homopolysaccharide

A polysaccharide consisting of only one type of monosaccharide unit.

heteropolysaccharide

A polysaccharide consisting of two o more types of monosaccharides.

Which of the following statements correctly describe amylose and amylopectin, two forms of starch?

Amylopectin is a branched form of starch. Amylose consists of an unbranched skeleton of glucose molecules. Amylose and amylopectin are both soluble in water.

Which two functional groups are attached to the same carbon in a hemiacetal?

An alkoxy (OR) group; a hydroxyl (OH) group

Which of the following are Ketones?

C and D

Which of the following statements correctly describe cellulose?

Cellulose is found in the cell walls of nearly all plants. Cellulose is an unbranched polymer of repeating glucose units. Cellulose is an enzyme that is capable of cleaving the glycoside bonds in cellulose.

Dextrorotatory

Clockwise rotation (+) specific rotation

Levorotatory

Counterclockwise rotation (-) specific rotation. (think left hand)

Amino sugar

Derivative in which the terminal -CH2OH group of the monosaccharide is oxidized to a carboxylate group (COO-).

Uronate

Derivative in which the terminal -CH2OH group of the monosaccharide is oxidized to a carboxylate group.

_____ are stereoisomers that are nonsuperimposable mirror images of one another.

Enantiomers

Alpha amylase

Enzyme that cleaves amylose at random sites along the chain

Beta amylase

Enzyme that cleaves amylose into maltose disaccharides

Maltase

Enzyme that hydrolyzes maltose into glucose

Which two monosaccharides constitute the disaccharide lactose?

Glucose; galactose

Select all of the following that correctly describe the polysaccharide glycogen.

Glycogen is similar to amylopectin but contains more and shorter branches. Glycogen contains both alpha(1to4) and alpha(1to6) glyosidic linkages.

A flat, six-membered ring structure used to represent the cyclic hemiacetals of glucose and other sugars is known as a ______.

Haworth projection

What structure gives the correct Haworth projection for B-D-talose?

It's C.

T/F: Cyclization of fructose produces a-D-fructose, with the -OH group at carbon-2 in the "down" position, and B-D-fructose, with the -OH group at carbon-2 in the "up" position.

T

T/F: Sucrose is heated and decomposes into glucose and fructose. The decomposition then begins a series of reactions that produce small molecules and polymers, including caramelans, caramelens, and carmelins.

T

A disaccharide is describe as having a B(1to3) glyosidic linkage. Select all the statements that correctly interpret this information.

The glycosidic bond links C-1 of one ring to C-3 of the other. The glycosidic bond is oriented up with respect to the ring linked at C-1.

alpha glycoside

The glycosidic linkage is oriented down, below the plane of the ring that contains the acetal joining the monosaccharides.

beta glycoside

The glycosidic linkage is oriented up, above the plane of the ring that contains the acetal joining the monosaccharides.

Pancreas

Where amylose degradation enzymes are produced.

Saliva

Where amylose degradation enzymes are secreted.

How do enantiomers differ in their physical properties? a) They rotate plane-polarized light in opposite directions. b) They have slightly different solubilities in water. c) They have different melting points. d) They exist in different physical states.

a

Which of the following statements correctly describe galactose? a) Galactose is one of two monosaccharides that make up lactose. b) Galactose is a pentose. c) Galactose is a hexose d) Galactose has a ketone functionality.

a and c

An ______ glycosidic bond is the linkage between the C-1 hydroxyl group of a alpha-D-glucose and the C-4 of another glucose molecule.

a(1to4)

Which of the following statements correctly describe fructose? a) Fructose has a ketone functional group b) Fructose is found in honey c) Fructose is sweeter than table sugar d) Fructose has an aldehyde functional group e) Fructose has five carbons

a, b, c

Which of the following statements correctly describe carbohydrates? a) Carbohydrates include sugars and starches. b) Carbohydrates include only polyhydroxy aldehydes. c) Carbohydrates are hydrates of amino acids. d) Simple sugars are molecules with the simple formula CnH2nOn.

a, d

The enzyme _____ cleaves the glycosidic bonds of the amylose chains at random, while the ____ enzyme sequentially cleaves the disaccharide maltose from the reducing end of the amylose chain.

a-amylase; B-amylase

All disaccharides contain at least one _____ that forms part of the link between two rings.

acetal

A four-carbon monosaccharide with an aldehyde carbonyl group at carbon-1 (c1) is correctly classified as a(n) ______.

aldose

Starch is a heterogenous material composed of which glucose polymers?

amylose and amylopectin.

Starch is composed of ______, an unbranched skeleton of glucose molecules that adopts helical structure, and _______, highly branched skeleton of glucose molecules.

amylose; amylopectin

glucose oxidase

an anzyme that catalyzes the conversion of glucose into gluconic acid and hydrogen peroxide

peroxidase

an enzyme that catalyzes the reaction of peroxide and orthotolidine to produce a blue pigment on the urine test strip

benedict's reagent testing

an older testing that ranges in colors from blue to red solutions to indicte concentration of glucose in the urine

Which of the following correctly describes diastereomers? a) Chiral compounds that don't have the same chem formula b) Stereoisomers that are not mirror images of each other c) unequal mixtures of enantiomers d) constitutional isomers of chiral compounds

b

Which of the following properly describe a chiral carbon? a) A carbon atom that is bonded to four other carbon atoms. b) A carbon atom that is bonded to four different groups. c) A carbon atom with trigonal planar geometry. d) Any tetrahedral carbon atom.

b

Select all of the following that correctly describe meso compounds. a) Meso compounds contain no chiral carbon atoms. b) Meso compounds are achiral c) Meso compounds have an internal plane of symmetry d) Meso compounds contain chiral carbon atoms. e) Meso compounds are optically active.

b, c, d

Which of the following statements correctly describe monosaccharides? a) Monosaccharides contain numerous carbonyl groups. b) An aldose has a carbonyl group at carbon-1, at the top of the structure. c) An aldopentose contains a five-carbon chain with an aldehyde functional group. d) Monosaccharides are drawn vertically, with the carbonyl group placed at (or near) the top. e) A ketose has a carbonyl group at carbon-1 at the top of the structure.

b, c, d

Which of the following statements regarding galactosemia are correct? a) Left untreated, only mild side effects can occur. b) There is an absence of one or more enzymes needed to convert galactose to glucose for metabolism. c) This disease is also known as lactose intolerance. d) Galactosemia is a genetic disease in humans.

b, d

Examples of ____ include simple sugars and starches, all of which contain the same simple formula (CH2O)n.

carbohydrates

The polysaccharide ____ contains B1to4) glycosidic linkages between glucose molecules, is the primary component of the polant cell wall, and cannot be digested by humans.

cellulose

A molecule that cannot be superimposed on its mirror image, and therefore can exist in enantiomeric forms is called a ____ molecule.

chiral

A tetrahedral carbon atom that is bonded to four different atoms/groups is known as a(n) ____ carbon atom.

chiral

Molecules that are stereoisomers but are not mirror images of each other are known as _____.

diastereomers

The two nonsuperimposable mirror0image forms of a chiral molecule are called ____.

enantiomers

The configuration of the chiral carbon ____ the carbonyl group determines whether a monosaccharide is D- or L-. If the -OH group is on the right-hand side, the monosaccharide is the ____ form.

farthest from; D-

Cellulose contains structures called _____; these are long, rigid parallel chains of polymer held tightly together by hydrogen bonding.

fibrils

A simple, two-dimensional drawing that uses intersecting lines to represent the three-dimensional structure of a chiral carbon is known as a _______ Projection.

fischer

Glycogen is composed of _____ molecules nd has both a(1to4) and a(1to6) glyosidic bonds.

glucose

Sucrose is a disaccharide, composed of the monosaccharides ______ and ________.

glucose; fructose

A disaccharide is formed when two monosaccharides are joined through a bridging oxygen atom, creating a _____ bond.

glycosidic

The joining of two monosaccharides through bridging oxygen atoms creates what kind of bond

glycosidic bond

Which functional group is contained in the cyclic compound shown?

hemiacetal

An achiral (nonchiral) compound does not rotate the plane of plane-polarized light and is said to be optically ____.

inactive

a compound that contains both a hydroxyl group and a carbonyl group can undergo a self-cyclization reaction to form a stable _____ hemiacetal

intramolecular

Individuals who do not make the enzyme lactase are said to have ____.

lactose intolerance.

An intermediate in the hydrolysis of starch, _____ is a reducing sugar composed of two glucose molecules.

maltose

The disaccharide _____ is composed of two glucose molecules linked by an a(1to4) glyosidic bond.

maltose

A compound that contains chiral compounds but is not optically active is called a ____ compound.

meso

Lactose is the principal sugar in the ____ of most mammals.

milk

Aldoses are ______ with ____ to give carboxylic acids.

oxidized, benedict's reagent

Light that consists of waves in only one plane is known as _____ light.

plane-polarized

A _____ is an instrument that allows plane-polarized light to pass through a sample and measures any rotation of the light that may occur.

polarimeter

A carbohydrate that contains many monosaccharides joined together is called a ______.

polysaccharide

A mixture containing equal amounts of a pair of enantiomers is called a _____ mixture.

racemic

Sugars that are oxidized by Benedict's reagent are called ___ sugars.

reducing

Compounds that differ only in the spatial arrangement of their atoms are called ___.

stereoisomers

The disaccharide is produced by plants used primarily as a sweetener, and composed of glucose and fructose.

sucrose

B anomer

the OH group at the anomeric carbon is above the ring

a anomer

the OH group at the anomeric carbon is below the ring

glucose oxidase testing

the most common testing usually sold in kits to indicate the more accurate glucose levels

Monosaccharides generally contain ____ carbon atoms in a chain with a ____ group at either c-1 or c-2.

three to six; carbonyl

One group of monosaccharide derivatives is the _______, formed when the terminal -CH2OH group of a monosaccharide is oxidized to a carboxylate group. A second important group of derivatives is the _____, in which one of the hydroxyl groups is replaced with an amino group.

uronates; amino sugars

Benedict's reagent has been used to test for the presence of glucose in urine. A brick-red color changes indicates a(n) _____ concentration of glucose in the urine, while a blue solution indicates a(n) _____ concentration.

very high; insignificant.