Carbohydrates 1

Question 1

• serve as the major source of energy and as a reserve food material.
• form part of the structural framework of DNA and RNA molecules.
• are involved in cell-cell interaction.

Answer 1

Carbohydrates

Question 2

Classification of Carbohydrates

Answer 2

• Monosaccharide
• Oligosaccharides
• Polysaccharides

Question 3

o Contain single polyhydroxy aldehyde or ketone unit
o They can’t be broken down into simpler substances by hydrolysis (reaction with water) reactions
o Contains 3-7 C atoms
o 5 and 6 carbon species are more common
o Water soluble white crystalline solids

Answer 3

Monosaccharide

Question 4

o Contains ~2-10 monosaccharide units - covalently bonded to each other
o Disaccharides (contain 2 monosaccharide units) more common - crystalline water soluble substances
o Table sugar (sucrose) and milk sugar (lactose)
o - are common disaccharides
o Upon hydrolysis they produce monosaccharide
o In human body associated with proteins and lipids for structural and regulatory
functions

Answer 4

Oligosaccharides

Question 4

o Contains many monosaccharide units covalently bonded
o Polymers: May contain 100s of 1000s of monosaccharide units

Answer 4

Polysaccharides

Question 5

are isomers that have the same molecular and structural formulas but differ in the orientation of atoms in space

Answer 5

Stereoisomers

Question 5

are stereoisomers whose molecules are non-superimposable mirror images of each other. Molecules with chiral center.

Answer 5

Enantiomers

Question 5

are stereoisomers whose molecules are not mirror images of each other.

Answer 5

Diastereomers

Question 6

• a method for giving molecular chirality specifications in two dimensions. A __________ is a two-dimensional structural notation for showing the spatial arrangement of groups about chiral centers in molecules.

Answer 6

Fischer Projection Formula

Question 7

• The four groups attached to the atom at the chiral center assume a tetrahedral geometry and it is governed by the following conventions

Answer 7

Tetrahedral Arrangements

Question 7

• Chiral compound that rotates light towards right (clockwise; +)

Answer 7

Dextrorotatory

Question 8

• Chiral compound that rotates light towards left (counterclockwise; -)

Answer 8

Levorotatory

Question 9

Blood sugar- Main source of energy

Answer 9

D-glucose

Question 10

Constituent of sucrose, the common sugar

Answer 10

D-fructose

Question 11

Constituent of lactose, glycolipids and glycoproteins

Answer 11

D-galactose

Question 12

Constituent of globulins, mucoproteins, and glycoproteins

Answer 12

D-mannose

Question 13

o Dominant form of monosaccharides with 5 or more C atoms is cyclic - cyclic forms are in equilibrium with open chain form
o Cyclic forms are formed by the reaction of carbonyl group (C=O) with hydroxyl (-OH) group on carbon 5

Answer 13

Cyclic Hemiacetal Forms of D-glucose

Question 14

six-atom ring is called a

Answer 14

pyranose

Question 14

five-atom ring is called

Answer 14

furanose

Question 14

a two-dimensional structural notation that specifies the
three-dimensional structure of a cyclic form of a monosaccharide.

Answer 14

Hawort Projection Formula

Question 15

• Oxidation can yield three different types of acidic sugars depending on the type
  of oxidizing agent used:

Answer 15

Oxidation to acidic sugars

Question 16

• The carbonyl group in a monosaccharide (either
  an aldose or a ketose) is reduced to a hydroxyl group using hydrogen as the
  reducing agent.

Answer 16

Reduction to sugar alcohols

Question 17

• Cyclic forms of monosaccharides are hemiacetals, they react with alcohols to form acetals

Answer 17

Glycoside formation

Question 18

• and their N-acetyl derivatives are important building blocks of polysaccharides such as chitin

Answer 18

Amino sugar formation

Question 18

* of various monosaccharides are stable in aqueous solution and play important roles in the metabolism of carbohydrates

Answer 18

Phosphate ester formation

Question 19

* Two monosaccharides can react to form ___________ * One monosaccharide act as a hemiacetal and other as alcohol

Answer 19

Disaccharides

Question 20

is digested easily by humans because we have enzymes that can break a (1-4) linkages but not b (1-4) linkages of cellobiose. Therefore cellobiose cannot be digested by humans.

Answer 20

Maltose

Question 21

is made up of b-D-galactose unit and a b-D-glucose unit joined by a b(1-4) glycosidic linkage

Answer 21

Lactose

Question 22

o Many monosaccharide units bonded with glycosidic linkages o Two types: ▪ - Linear and branched, homo- and hetero-polysaccharides

Answer 22

Polymers

Question 23

A storage polysaccharide is a polysaccharide that is a storage form for monosaccharides and is used as an energy source in cells.

Answer 23

Starch

Question 24

Branched chain polymer - 80 - 85 % of the starch a (14) glycosidic bond for straight chain and a (16) for branch

Answer 24

Amylopectin

Question 25

▪ Humans and animals storage polysaccharide ▪ Contains only glucose units

Answer 25

Glycogen

Question 26

▪ Linear homopolysaccharide with b (1  4) glycosidic bond ▪ It serves as dietary fiber in food-- readily absorbs water and results in softer stools

Answer 26

Cellulose

Question 27

▪ Similar to cellulose in both function and structure ▪ Linear polymer with all b (14) glycosidic linkages - it has a N-acetyl amino derivative of glucose ▪ Function is to give rigidity to the exoskeleton s of crabs, lobsters, shrimp, insects, and other arthropods

Answer 27

Chitin

Question 28

polysaccharides with a repeating disaccharide unit containing an amino sugar and a sugar with a negative charge due to a sulfate or a carboxyl group.

Answer 28

Acidic Polysaccharides

Question 29

is a lipid molecule that has one or more carbohydrate (or carbohydrate derivative) units covalently bonded to it.

Answer 29

glycolipid

Question 30

\is a protein molecule that has one or more carbohydrate (or carbohydrate derivative) units covalently bonded to it.

Answer 30

glycoprotein

Question 31

are polyhydroxy aldehydes, polyhydroxy ketones, or compounds that yield such substances upon hydrolysis. Plants contain large quantities of carbohydrates produced via photosynthesis

Answer 31

Carbohydrates

Question 32

A chiral object is not identical to its mirror image. An achiral object is identical to its mirror image.

Answer 32

Chirality and achirality

Question 33

The atoms of stereoisomers are connected in the same way but are arranged differently in space. The major causes of The atoms of ________________ in molecules are structural rigidity and the presence of a chiral center.

Answer 33

stereoisomers

Question 34

are two-dimensional structural formulas used to depict the three-dimensional shapes of molecules with chiral centers

Answer 34

Fischer projection formulas

Question 34

re two-dimensional structural representations used to depict the three-dimensional structure of a cyclic form of a monosaccharide.

Answer 34

Haworth projection formulas