Monosaccahrides and Disaccharides

What are carbohydrates used for?

They are a group of substances used as both energy resources and structural materials in organisms

What 3 elements do all carbohydrates contain?

• carbon

• Hydrogen

• Oxygen

What is the general formula for all carbohydrates?

Cx(H20)y

What are the 3 main groups of carbohydrates?

• monosaccharides

• Disaccharides

• Polysaccharides

What are monosaccharides and what are their general formula?

Simple sugars (CH2O)n (n being any number from 3 - 7)

What are disaccharides?

Double sugars formed from 2 monosaccharides

What are polysaccharides

Large molecules formed from many monosaccharides

What are the 3 main monosaccharides we need to know?

• glucose

• Fructose

• Galactose

What are the 3 main disaccharides we need to know?

• sucrose

• Lactose

• Maltose

What are the three main polysaccharides we need to know?

• glycogen

• Starch

• Cellulose

What is the difference between polysaccharides like glycogen and starch vs cellulose

Glycogen and starch are storage carbohydrates and cellulose is a structural carbohydrate

What is another name for a monosaccharide?

Reducing sugar

What kind of solid do monosaccharides form?

White crystalline solids

What type of sugar is glucose?

A heroes sugar → 6 carbon atoms

What are 3 characteristics of glucose?

• highly soluble

• Major energy source

• Main form in which carbs are transported in animals

What are structural isomers?

Molecules with the same chemical formula and different structural one

What is the structural difference between an alpha and beta glucose molecule?

The -OH group in alpha is below on carbon 1 and above on beta

What does the difference in structures affect in alpha and beta glucose?

It is the reason why alpha glucose is easily digestible to human but beta is not

What do alpha glucose form to make vs beta glucose?

Alpha → starch, beta → cellulose

What are some characteristics of fructose?

• sweeter than glucose

• Main sugar in fruits

• Pentagon shape even though it is a hexose

• Not as soluble as nectar

• Important in glycolipids production

What are two pentose monosaccharides?

Ribose and deoxyribose

What are ribose and deoxyribose important for?

RNA and DNA respectively

What is the structural difference between ribose and deoxyribose?

Ribose has one H atom and -OH group attached to carbon 2 whereas deoxyribose has only 2 H atoms on carbon 2

How do monosaccharides form disaccharides?

Through a condensation reaction, removing an H2O from the two monosaccharides reacting

What is the name of the bond formed in a disaccharide?

A glycosidic bond

Glucose + glucose → ?

Maltose

Glucose + sucrose → ?

Sucrose

Beta glucose + Galactose → ?

Lactose

What is the liquid used to test for reducing sugars?

Using Benedict’s reagent

What is Benedict’s reagent?

A turquoise liquid with Cu²+ ions in an alkaline solution

What happens if reducing sugars are present?

Copper is reduced to Cu+ and the solution turns brick red

What extra step must be done with non-reducing sugars to test with Benedict’s?

It must be first boiled in a dilute acid to neutralise and break the glycosidic bonds, where the solution must react to