Chapter 3: Macromolecule of the Cell Carbohydrates/Polysaccharides

What four classes of biological macromolecules are listed on the cell biology slide?

Carbohydrates/polysaccharides

Nucleic acids

Proteins

Lipids

What is a polysaccharide?

A long-chain polymer of sugars and sugar derivatives

What are the two primary functions of polysaccharides?

Structure and Storage

What type of repeating units usually make up polysaccharides?

A single kind of repeating unit or an alternating pattern of two kinds

What is a polymer?

A large molecule made of repeating smaller units connected together

What is an oligosaccharide?

A short polymer of sugars

Where can oligosaccharides be found according to the slide?

Attached to cell-surface proteins

What is the basic difference between a polysaccharide and an oligosaccharide?

A polysaccharide is a long sugar polymer, while an oligosaccharide is a short sugar polymer

If a biological molecule is a long chain of repeating sugar units, what class of molecule is it?

A polysaccharide

What are the repeating units, or monomers, of polysaccharides?

Monosaccharides

What two features are used to classify monosaccharides on this slide?

The location of the carbonyl group and the number of carbon atoms

What is a carbonyl group?

A C=O group

What is an aldosugar?

A sugar with a terminal carbonyl group

What is a ketosugar?

A sugar with an internal carbonyl group

A sugar has its C=O at the end of its carbon chain. What type of sugar is it?

An aldosugar

A sugar has its C=O within the carbon chain rather than at the end. What type of sugar is it?

A ketosugar

What are monosaccharides with 3, 5, and 6 carbons called?

3 C = triose; 5 C = pentose; 6 C = hexose

How can you systematically classify an unfamiliar monosaccharide structure?

Find the C=O to determine aldo vs. keto, then count the carbons to determine triose, pentose, or hexose

What is the most common monosaccharide?

D-glucose

What is the molecular formula of glucose?

C₆H₁₂O₆

What type of sugar is glucose?

An aldohexose

Why is glucose classified as an aldohexose?

It has a terminal carbonyl group and 6 carbon atoms

From which end are the carbons of glucose numbered?

From the more oxidized carbonyl end

What structure does glucose adopt in aqueous solution?

A ring structure

How can you distinguish α-D-glucose from β-D-glucose?

In α-D-glucose, the C1 hydroxyl group points down; in β-D-glucose, it points up.

A glucose ring has its hydroxyl group on carbon 1 pointing down. Is it α- or β-glucose?

α-glucose

A glucose ring has its hydroxyl group on carbon 1 pointing up. Is it α- or β-glucose?

β-glucose

Which polysaccharides use α-D-glucose versus β-D-glucose as repeating units?

α-D-glucose → starch and glycogen; β-D-glucose → cellulose

What is a disaccharide?

A carbohydrate formed when two monosaccharides are joined

What type of bond joins two monosaccharides in a disaccharide?

A glycosidic bond

What happens to water when a glycosidic bond forms between two monosaccharides?

Water is eliminated

How are monosaccharides, glycosidic bonds, and disaccharides related?

Two monosaccharides are joined by a glycosidic bond to form a disaccharide

What are the two ring forms of D-glucose, and how are they distinguished?

α-D-glucose has its C1 hydroxyl pointing down, while β-D-glucose has its C1 hydroxyl pointing up

How does the α or β form of a sugar relate to glycosidic bonds according to the disaccharide slide?

The α form is associated with an α glycosidic bond, while the β form is associated with a β glycosidic bond

Which two monosaccharides are joined to form maltose in the slide’s figure?

α-D-glucose + α-D-glucose

What type of glycosidic bond is shown in maltose on the disaccharide slide?

An α glycosidic bond

Which two monosaccharides are joined to form lactose in the slide’s figure?

β-D-galactose + β-D-glucose

What type of glycosidic bond is shown in lactose on the disaccharide slide?

A β glycosidic bond

Which two monosaccharides are joined to form sucrose in the slide’s figure?

α-D-glucose + β-D-fructose

What type of glycosidic bond is labeled in sucrose on the disaccharide slide?

An α glycosidic bond

If a disaccharide structure contains two glucose units joined by an α glycosidic bond, which example from the slide is it?

Maltose

If a disaccharide structure contains galactose and glucose joined by a β glycosidic bond, which example from the slide is it?

Lactose

If a disaccharide structure contains glucose and fructose, which example from the slide is it?

Sucrose

How does elimination of water lead to formation of a disaccharide?

Water is eliminated as two monosaccharides become joined by a glycosidic bond

What visual feature connects the two monosaccharides in the disaccharide structures shown on the slide?

An oxygen-containing glycosidic linkage between the sugar units.