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SURVEY OF BIOCHEMISTRY

Carbohydrates

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What are Carbohydrates?

• Generic Formula of Simple Carbs(CH2O)n

• Sugars formed from CO2 and H2O

• Roles– Energy in diet– Mediating intercellular communication– Structural support (e.g. cell walls)

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Classification

• Monosaccharides– Aldoses– Ketoses

• Polysaccharides (Glycans, Glycosides)

• Glycoproteins: sugars bound to proteins– N-linked Oligosaccharides– O-Linked Oligosaccharides

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Aldoses & Ketoses

Sugars made from aldehydes form aldoses

Sugars made from ketones form ketoses

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Important Aldoses To Study

5-Csugar

6-C sugars

All begin with CHO group

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Important Aldoses To Study

5-Csugar

6-C sugars

All end with group

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Important Aldoses To Study

5-Csugar

6-C sugars

Most names end with -ose suffix

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Important Ketoses To Study

Most names all end with -ulose suffix

5-Csugar

3-Csugar

6-Csugar

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Important Ketoses To Study

Ketoses begin with group

5-Csugar

3-Csugar

6-Csugar

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Important Ketoses To Study

Most ketoses end with group

5-Csugar

3-Csugar

6-Csugar

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Important Ketoses To Study

Several ketoses end with -ulose suffix

5-Csugar

3-Csugar

6-Csugar

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Structures of Monosaccharides

• Isomers and Epimers

• Enantiomers

• Anomeric Carbons

• Ways to Draw Monosaccharides– Fischer Projection– Haworth Projection– Chair form

Preferred

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Isomers

• Isomers are different compounds that have the same chemical formula

C6H12O6

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Epimers

Epimers are sugars that differ only by the configuration around one carbon atom.

Only difference

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Enantiomers

Most sugars are found in the D-stereoisomer.D-Glyceraldehyde is the most simple aldose.

See Section

4-2 for help

Know this structure

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Cyclization of MonosaccharidesAnomeric Carbons

AnomericCarbon

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Cyclization of MonosaccharidesAnomeric Carbons

AnomericCarbon

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αConformations Position of -OH Group on Anomeric C

Down

Up

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β

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Ways to Draw Monosaccharides

• Fischer Projection - linear• Haworth Projection - cyclic• Chair - cyclic

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α

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β

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Cyclization of Monosaccharides

DownUp

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Cyclization of Monosaccharides

DownUp

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Polysaccharides

• Disaccharides: 2 sugars– Lactose: Glucose + Galactose– Sucrose: Glucose + Fructose– Maltose: Glucose + Glucose

• Oligosaccharides: 3-12 sugars

• Polysaccharides: 13+ sugars– Glycogen: homopolysaccharide of glucose– Glycosaminoglycans: heteropolysaccharides

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Polysaccharides

Monosaccharides can be linked to form oligosaccharides,and ultimately polysaccharides via glycosidic bonds.

Glycosidic Bond

SUCROSE

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Polysaccharides

Monosaccharides can be linked to form oligosaccharides,and ultimately polysaccharides via glycosidic bonds.

Glycosidic Bond

LACTOSE

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Glycosidic Bonds in RNA

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Starch in Plants

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Starch in Plants

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Glycoproteins: N-Linked

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Glycoproteins: O-Linked

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PRS

• When comparing two enzymes, the optimal catalytic activity can be determined by_______.

1. The smallest Km

2. The largest KM

3. The smallest Vmax

4. The smallest kcat/KM

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PRS

• Which class of enzyme catalyzes group elimination to form double bonds?

1. Transferases2. Isomerases3. Lyases4. Ligases

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PRS

• Which of the following proteins is involved in muscle contraction?

1. Trypsin2. Troponin3. Chymotrypsin4. Hemoglobin

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PRS

• Which of the following is a ketose?

1. Glucose2. Fructose3. Ribose4. Galactose