Topic 27: Structures of Simple Sugars

Trehalose (insect sugar)

-A1-A1 bond -Glucose (Glu) linked to glucose (Glu) between the 2 anomeric carbons to form the disaccharide Glc (a1-a1) Glc

Reducing sugars

-Carbohydrates that react with oxidizing agents (i.e. Cu2+) -Generally aldoses

Disaccharides

-Contain 2 simple sugars covalently linked by an O-glycosidic bond (the bond can be either in the a or b conformation) -For example, lactose contains glucose and galactose with a b (1-4) bond

Lactose (milk sugar)

-Contains a B (1-4) glycosidic bond -Links a galactose (Gal) to a glucose, forming Gal (B1-4) Glc

Enantiomers

-Exist in nature as either right-handed (D form) or left-handed (L form) isomers -Differentially rotate polarized light

Lactase

-Expressed in high levels in infants to aid in digestion of lactose -Declines in adults

Example of Monosaccharides

-Glucose -Fructose Galactose

Sucrose (table sugar)

-Made in plants and used as table sugar in its crystalline form -Contains an a1-B2 bond -Fructose (Fru) linked to glucose through 2 anomeric carbons, forming Glc (a1-B2) Fru

Glucose is a ______________

-Polyhydroxyaldehyde

Fructose is a _____________

-Polyhydroxyketone

Haworth Projections

-Simple sugars go through an intramolecular reaction to form either pyranose or furanose rings -This increases structural stability -The naming convention changes

Benedicts Test

-Sugars that react with copper (Cu2+) are called reducing sugars (glucose, galactose, lactose) -Sugars that do not react are called non-reducing sugars

Disaccharides

-Two mono-saccharides linked together through an O-glycosidic bond -Formed through a condensation reaction

Benedict's Test

-Uses an alkaline solution of copper as a mild oxidizing agent -The reduction of Cu2+ to Cu+ changes the color from blue to red, as a result of the formation of a copper oxide precipitate

Chiral center

An atom with four different functional groups

Bonds to each carbon are either __________ or __________

Axial Equatorial

Pyranose rings such as glucose adopt 2 conformations: ____________ and ____________

Chair conformation Boat conformation

Sugars taste sweet and are found naturally in __________ and _________

Fruits Vegetables

In reducing sugars, simple sugars can be oxidized or reduced based on their ____________

Functional groups

_____________ is the most plentiful monosaccharide in nature

Glucose

Simple sugars are metabolites that feed into the glycolytic pathway, such as aldose sugars like _______ and ketose sugars like _________

Glucose Fructose

Lactase is a ___________ enzyme

Hydrolytic

What are 3 common disaccharides?

Lactose, Sucrose, Trehalose

Sugars that do not react are called ____________

Non-reducing sugars

Monosaccharide

One sugar containing an aldehyde (aldose) or a ketone (ketoses)

Pyranose rings such are glucose are not ________

Planar

Sugars that react with copper are called __________

Reducing sugars

Glyceraldehyde

Smallest monosaccharide triose sugar with one chiral ceneter

Epimers

Two monosaccharides that differ in the position of the OH group around one chiral carbon