Carbohydrates Biochemistry

Question 1

What are carbohydrates?

Answer 1

Essential components of all living organisms and is the most abundant biological molecule on the planet

Question 2

What is biosynthesis?

Answer 2

Structural building blocks+energy storage

Question 3

What is catabolism?

Answer 3

Carbon fuels that drive biological processes.

Question 4

What is an aldose sugar?

Answer 4

An aldose sugar is a molecule that has an aldehyde functional group on C1 of the molecule.

Question 5

What are the two types of sugars that can be formed?

Answer 5

Aldose sugars or ketose sugars.

Question 6

What are ketose sugars?

Answer 6

Ketose sugars have a ketone functional group on carbon 2 of the sugar molecule.

Question 7

What are the simiplest carbohydrates?

Answer 7

The simplest carbohydrates is a molecle that is three carbons long in length and is either an aldose sugar or a ketose sugar.

Question 8

What is an aldotriose?

Answer 8

A 3C long sugar molecule with an aldehyde functional group at C1.

Question 9

What is a ketotriose?

Answer 9

A 3C long sugar molecule with a ketone functional group at C2.

Question 10

What are monosaccharides?

Answer 10

The basic unit of carbohydrates.

Question 11

Where do monosaccharides come from?

Answer 11

Synthesized from simpler substances in gluconeogenesis or photosynthesis.

Question 12

What is the role of monosaccharides??

Answer 12

Major energy source, and components of nucleic acids, and lipid and protein modification.

Question 13

What are oligosaccharides?

Answer 13

Consist of few covalently linked monosaccharides (2~20)
- associated with proteins and lipids
- serve structural and regulatory roles

Question 14

What are polysaccharides?

Answer 14

Consist of ~20 or more covalently linked monosaccharides.
- structural function in all organisms
- nutritional reserve

Question 15

What are enantiomers?

Answer 15

Nonsuperimposable mirror images of one another

Question 16

What are the two stereoisomers formed by carbohydrates?

Answer 16

L and D

Question 17

What is the most common stereoisomer that carbohydrates exist in?

Answer 17

D conformation of the stereoisomer.

Question 18

How to identify if a carbohydrate is in either the Lor D conformation?

Answer 18

Look at the chiral carbon farthest away from the carbonyl carbon.

> OH on left : L isomer
OH on right: D isomer

Question 19

What is the conformation of a carbohydrate whose farthest chiral carbon (from the carbonyl carbon) has the OH functional group pointing to the left?

Answer 19

The conformation of the carbohydrate is the L conformation.

Question 20

What is the conformation of a carbohydrate whose farthest chiral carbon (from the carbonyl carbon) has the OH functional group pointing to the right?

Answer 20

The conformation of the carbohydrate is the D conformation.

Question 21

What is the proper name of sugar molecules 3C long?

Answer 21

(Aldo/Keto) Trioses

Question 22

What is the proper name of a sugar molecule that is 4C long?

Answer 22

(Aldo/keto) Tetroses

Question 23

What is the proper name for sugar molecules that are 5C long?

Answer 23

(Aldo/Keto) Pentoses

Question 24

What is the proper name for sugar molecules 6C long?

Answer 24

(Aldo/Keto) Hexoses.

Question 25

What are diastereomers?

Answer 25

Differ at two or more chiral centers (BUT NOT ALL)

Question 26

What are enantiomers?

Answer 26

Differ at ALL chiral centers (mirror image molecules).

Question 27

What are epimers?

Answer 27

Differ at ONE chiral center.

Question 28

How to determine the number of chiral carbons in a sugar molecule?

Answer 28

#C-2= # of chiral C in sugar molecule

Question 29

How to determine the number of stereoisomers?

Answer 29

2^n, where n is the number of chiral centers in the molecule. Half are D and half are L.

Question 30

What results from a reaction containing alcohols and aldehydes in a 1:1 ratio?

Answer 30

Form hemicaetals and (2:1 ratio) acetals.

Question 31

What results from a chemical reaction of alcohols and ketones in a 1:1 ratio?

Answer 31

Formation of hemiketals and (2:1 ratio) ketals.

Question 32

Draw the cyclization of glucose.

Question 33

What is the name of C1 after cyclization of glucose?

Answer 33

It is known as the anomeric carbon (it is a reduced C)

Question 34

What happens to the hydroxyl group during the cyclization of glucose?

Answer 34

It becomes a cyclic ether after cyclization has occured.

Question 35

What are the name of 5 member rings?

Answer 35

Furanose

Question 36

What is the name for 6 membered rings?

Answer 36

Pyranose

Question 37

Draw a generic structure of the formation of a pyranose ring.

Question 38

Draw a generic structure of the formation of a furanose ring.

Question 39

Draw the structure for beta-D-2-Deoxyribose.

Question 40

What is the anomeric carbon?

Answer 40

The hemiacetal or hemiketal carbon.

Question 41

What happens through cyclization?

Answer 41

Two different anomers (C1 or C2 => chiral) are formed.

Question 42

What is an alpha anomer?

Answer 42

Anomeric carbon OH is on the oposite side of the ring from the CH2OH of the chiral C (center) defining D or L.

Question 43

What is a beta anomer?

Answer 43

Anomeric carbon OH is on the same side of the ring as the CH2OH of the chiral C (center) defining D or L.

Question 44

Draw the structure of alpha-D-Glucopyranose and beta-D-Glucopyranose.

Question 45

Draw the structure for alpha-D-fructofuranose and beta-D-fructofuranose.

Question 46

What is mutarotation?

Answer 46

The alpha and beta anomeric forms of monosaccharides (and free reducing ends of polymerized sugars) are in equilibrium. Spontaneous interconversion between anomeric forms.

Question 47

Draw the cyclization of fructose.

Question 48

Why does fructose exist in a furanose ring conformation than a pyranose ring conformation even though it is 6C long?

Answer 48

Fructose is more chemically stable when it is in a 5 member ring (furanose ring conformation) than a 6 member ring conformation (pyranose ring conformation).

Question 49

What are glycosidic bonds?

Answer 49

Condensation reaction between anomeric carbon and any other hydroxyl containing compound.

Question 50

What results from the production of a glucosidic bond?

Answer 50

Results in chemical formation of Acetal or Ketal

Question 51

What is the most common glycosidic bond observed in disaccharides?

Answer 51

Glycosidic bond from C1 to C4.

Question 52

What are other possible glycosidic bonds that can form?

Answer 52

C1 to C6 C1 to C1

Question 53

Draw the structure of lactose.

Question 54

Draw the structure of trehalose.

Question 55

Draw the structure of sucrose.

Question 56

How is a glycosidic bond named?

Answer 56

alpha/beta-number of anomeric carbon, alpha/beta if also anomeric/number of alcohol carbon

Question 57

Characteristics of polysaccharides.

Answer 57

- variable in length - can be comosed of one or more types of monosacharides - can be linear or branched

Question 58

What are homopolysaccharides?

Answer 58

Composed of one monosaccharide type (same monosaccharide) and can be unbranched or branched

Question 59

What are heteropolysaccharides?

Answer 59

Composed of two or more monosaccharide types (different monosaccharides) and can be unbranched or branched

Question 60

What is cellulose?

Answer 60

- Unbranched beta1-4 linked glucose - serves structural role in plants - indigestible by mammals

Question 61

Draw the structure for cellulose and label glycosidic linkage.

Question 62

What is amylose?

Answer 62

Unbranched alpha1-4 linked D-glucose

Question 63

Draw the structure of amylose and label the glycosidic linkage.

Question 64

What is glycogen?

Answer 64

Amylose with alpha1-6 branch every 8-12 residues

Question 65

Draw the structure of glycogen and indicate the glycosidic linkage and the branch points.