Carbohydrates

Question 1

What is the difference between an aldose and a ketose?

Answer 1

Aldose: Carbonyl group on C1

Ketose: Carbonyl group in internal carbon (usually C2)

Question 2

What is an X-ose? (x = tri, tetr, pent, hex)

Answer 2

An aldehyde or a ketose with a certain number of carbons

Question 3

How many stereoisomers do aldohexose and ketohexose have, and what does that mean for the number of chiral centres?

Answer 3

Aldohexose: 4 chiral centers, 16 stereoisomers

Ketohexose: 3 chiral centres, 8 stereoisomers

Question 4

What is the difference between D- and L- glyceraldehyde?

Answer 4

D: OH on carbon 2 is on the right
L: OH on carbon 2 is on the left

Question 5

What is the difference between enantiomers, diastereomers, and epimers?

Answer 5

Enantiomer: pair of nonsuperimposable mirror images

Diastereomer: pair non-mirror image stereoisomers

Epimer: diastereomers that are identical minus configuration at one chiral C

Question 6

What is the difference between a hemiacetal and a hemiketal?

Answer 6

Hemiacetal: aldehyde + alcohol

Hemiketal: ketone + alcohol

Question 7

How is glycopyranose formed?

Answer 7

C1 binds with OH of C5 to form a 6 membered ring

Question 8

What are anomers?

Answer 8

Isomers that differ only at hemiacetal or hemiketal C in glucopyranose.

Question 9

How is the alpha and beta glucopyranose anomers different?

Answer 9

Alpha: OH on C1 is on opposite sides of C6

Beta: OH on C1 is on the same side of C6

Question 10

What is mutarotation?

Answer 10

Interconversion between alpha and beta anomers in glucopyranose, measured by the rotation of plane polarized light.

Question 11

What is the difference in mutorotation of alpha and B glucose?

Answer 11

alpha: rotates light +112º

beta: rotates light +19º

Question 12

Why is beta glucose more abundant than alpha glucose?

Answer 12

Beta-D-Glc can put bulky substituents in the equatorial position in its chair conformation.

Question 13

What is glucitol?

Answer 13

Sugar derivative formed from the reduction (H gain) of the aldehyde on glucose to glycerol. (CH=O becomes CH2(OH))

Question 14

How are monosaccharides reducing agents?

Answer 14

Linear aldoses give up the H (oxidation) on their aldehyde group to form a carboxyl group.

Question 15

What are sugar phosphate esters?

Answer 15

Intermediates in sugar synthesis that prevent transport of sugar across membranes by adding phosphates in place of OH to “disguise” sugars.

Question 16

What are amino sugars?

Answer 16

Intermediates in sugar synthesis that prevent transport of sugar across membranes by adding phosphates in place of OH to “disguise” sugars.

Question 17

What are amino sugars?

Answer 17

Sguars that have an amide group replacing OH groups

Question 18

What is a sugar amide?

Answer 18

compound formed when a sugar reacts with an amide group (-CONH₂). (e.g. N-acetylglucosamine.)

Question 19

What is a deoxysugar?

Answer 19

Sugar in which the carbon 2 has two H2 bound instead of H and OH

Question 20

What is an acetal and a ketal?

Answer 20

Non reducing, non mutarotating compound formed when a hemiacetal/hemiketal undergoes heated dehydration when reacted with an alcohol.

Question 21

How is maltose made?

Answer 21

C1 of alpha glucose forms linear glycosidic bond with OH on C4 of another glucose

Question 22

How is isomaltose formed?

Answer 22

C1 of alpha glucose forms a vertical glycosidic bond with the OH on C6 of another glucose.

Question 23

what is the difference in formation of cellobiose and lactose?

Answer 23

Cellobiose: Glc(B1-4)Glc

Lactose: Gal(B1-4)Glc

Question 24

How is sucrose made?

Answer 24

The C1 on alpha glucose forms a vertical glycosidic bond with the OH on C2 of beta fructose.

Question 25

What makes a disaccharide reducing?

Answer 25

If it has a hemiketal or hemiacetal available to open up, linearize, and become oxidized.

Question 26

What is invert sugar?

Answer 26

A mixture of glucose and fructose as a result of hydrolysis of sucrose. Called invert due to inversion from +66º rotation as sucrose to -39º rotation in the mixture.

Question 27

how is trehalose made?

Answer 27

Glc(a1 - a1)Glc; non reducing, non mutorotating sugar used for energy storage in insects.

Question 28

What are oligosaccharides?

Answer 28

Oligosaccharides are short chains of a few sugars. Important when attached to proteins or lipids on the outside of various animal cells.

Question 29

What are some of the uses of oligosaccharides?

Answer 29

Cell-cell interactions in the nervous system, coating blood cells, ABO system

Question 30

What are polysaccharides?

Answer 30

Long chains of sugar connected by the same kinds of glycosidic bonds (a1-4) or (b1-4). They play roles in storage of sugar and structure.

Question 31

What is starch?

Answer 31

Storage form of D-Glc in plants. Include amylose and amylopectin.

Question 32

What is the difference between amylose and amylopectin.

Answer 32

Amylose: long unbranched chains of a(1-4) that form a helix amylopectin: chains of amylose linked by a(1-6) and does not form a helix.

Question 33

What is glycogen?

Answer 33

Animal cell storage of Glc, similar to amylopectin but more branched.

Question 34

What is dextrans?

Answer 34

Bacterial polysaccharides with a(1-6), and a(1-2), and a(1-4) links.

Question 35

What is malting?

Answer 35

Enzyme-catalyzed hydrolysis that produced sugar for fermentation

Question 36

What is cellulose?

Answer 36

Linear chain of many glucose units linked in D-cellobiose formed by B(1-4) linkkages. Strong rod like structure of parallel chains that undergo H bonding.

Question 37

What is peptidoglycan?

Answer 37

Alternating B(1-4) linked N-acetylglucosamine and N-acetylmuramic acid sugars, cross linked by peptides. Form a 3 dimensional mesh like cell wall structure in bacteria cell walls.

Question 38

what is a lysozyme?

Answer 38

enzyme that degrades bacterial cell walls by catalyzing the hydrolysis of B(1-4) linkages between N-acetylmuramic acid and N-Acetylglucosamine sugars in peptidoglycan