Biochemistry 4: Carbohydrate Structure and Function

Question 1

aldoses

Answer 1

carbohydrates that contain an aldehyde group as their most oxidized functional groups

carbonyl carbon can participate in glycosidic linkages

Question 2

ketoses

Answer 2

carbohydrates that contain a ketone group as their most oxidized functional groups

carbonyl carbon can participate in glycosidic linkages

Question 3

what sugar is this?

Answer 3

glyceraldehyde

Question 4

what sugar is this?

Answer 4

dihydroxyacetone

the simplest ketose

Question 5

what sugar is this?

Answer 5

D-glucose

Question 6

what sugar is this?

Answer 6

D-fructose

Question 7

what sugar is this?

Answer 7

D-galactose

Question 8

what sugar is this?

Answer 8

D-mannose

Question 9

sugars with the highest-numbered chiral carbon with the -OH group on the right

Answer 9

D-sugars

Question 10

sugars with the highest-numbered chiral carbon with the -OH group on the left

Answer 10

L-sugars

Question 11

enantiomers

Answer 11

D- and L-forms of the same sugar

nonsuperimposable compounds in which every chiral center is the opposite from each other

mirror images

Question 12

diastereomers

Answer 12

nonsuperimposable configurations of molecules with similar connectivity

differ in at least one (but not all) chiral carbons

Question 13

epimers

Answer 13

a subtype of diastereomers

differ at exactly one chiral carbon

Question 14

anomers

Answer 14

a subtype of diastereomers

differ at the anomeric carbon

Question 15

anomeric carbon

Answer 15

the new chiral center formed in the ring closure

in the straight-chain form, was the carbon containing the carbonyl group

Question 16

beta-anomer

Answer 16

glucose anomer

-OH group of C-1 is equatorial and up

cis to CH₂OH

Question 17

alpha-anomer

Answer 17

glucose anomer

-OH group of C-1 is axial and down

trans to CH2OH

Question 18

mutarotation

Answer 18

the shifting of cyclic compounds from one anomeric form to another with the straight-chain form as an intermediate

occurs in water

Question 19

fischer projection –?–> haworth projection

Answer 19

hemiacetal formation

Question 20

aldoses can be oxidized to ___ and reduced to ___

what about oxidation in ring form?

Answer 20

oxidized to aldonic acids

reduced to alditols (alcohols)

in cyclic form will be oxidized to lactones (cyclic ester with carbonyl at anomeric carbon)

Question 21

reducing sugars

Answer 21

sugars that are able to be oxidized

have hemiacetal rings

Question 22

Tollen’s reagent

[Ag(NH₃)₂]⁺

Answer 22

detects reducing sugars

when aldehydes are present, reagent will produce a silvery mirror

Question 23

Benedict’s reagent

Answer 23

detects reducing sugars

oxidizes aldehyde group when present, creating a red precipitate of Cu₂O

Question 24

tautomerization

Answer 24

the rearrangement of bonds in a compound, usually by moving a H to form a double bond

Question 25

enol

Answer 25

compound with double bond and alcohol group

ketones can’t be oxidized directly into COOH

instead tautomerizes to form aldose (keto-enol shifts), and reacts with Tollen’s or Benedicts reagents to form COOH

Question 26

deoxy sugar

Answer 26

reduced sugar with -H replacing an -OH group

(being reduced)

Question 27

hemiacetal + alcohol –> ______

Answer 27

acetal

anomeric OH interacts with an alkoxy group (CH chain bonded to alcohol) to create a glycosidic bond

Question 28

pyranose

Answer 28

saccharides that have a chemical structure that includes a six-membered ring consisting of five carbon atoms and one oxygen atom

Question 29

furanose

Answer 29

saccharides that have a chemical structure that includes a five-membered ring consisting of four carbon atoms and one oxygen atom

Question 30

sucrose

Answer 30

glucose-alpha-1,2-fructose

Question 31

lactose

Answer 31

galactose-beta-1,4-glucose

Question 32

maltose

Answer 32

glucose-alpha-1,4-glucose

Question 33

what sugar is this?

Answer 33

glucose

Question 34

cellulose

Answer 34

the main structural component for plant cell walls

beta-1,4 D-glucose glycosidic bonds

source of fiber for humans because we can’t digest the beta bonds

Question 35

starch

Answer 35

main energy storage form in plants

amylose - alpha-1,4 D-glucose glycosidic bonds

amylopectin - alpha-1,4 and alpha-1,6 D-glucose glycosidic bonds

amylopectin branches

Question 36

beta-amylase

Answer 36

enzyme that cleaves amylose at the nonreducing end (at the acetal)

Question 37

alpha-amylase

Answer 37

cleaves amylose randomly along the chain to yield short chains of maltose and glucose

Question 38

glycogen

Answer 38

main energy storage form for animals

alpha-1,4 and alpha-1,6 glucose glycosidic bonds

has more 1,6 linkages, creating more branches

more energy-efficient, allows more degrative enzymes to break it down