Ensayo

Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson

LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION

Chapter 5

The Structure and Function of Large Biological Molecules

Lectures by Erin Barley Kathleen Fitzpatrick
© 2011 Pearson Education, Inc.

Overview: The Molecules of Life
• All living things are made up of fourclasses of large biological molecules: carbohydrates, lipids, proteins, and nucleic acids • Macromolecules are large molecules composed of thousands of covalently connected atoms • Molecular structure and function are inseparable

© 2011 Pearson Education, Inc.

Concept 5.1: Macromolecules are polymers, built from monomers
• A polymer is a long molecule consisting of many similar building blocks• These small building-block molecules are buildingcalled monomers • Three of the four classes of life’s organic molecules are polymers
– Carbohydrates – Proteins – Nucleic acids

© 2011 Pearson Education, Inc.

The Synthesis and Breakdown of Polymers
• A dehydration reaction occurs when two monomers bond together through the loss of a water molecule • Polymers are disassembled to monomersby hydrolysis, hydrolysis, a reaction that is essentially the reverse of the dehydration reaction

Animation: Polymers
© 2011 Pearson Education, Inc.

Figure 5.2a

(a) Dehydration reaction: synthesizing a polymer
1 2 3

Short polymer Dehydration removes a water molecule, forming a new bond.

Unlinked monomer

1

2

3

4

Longer polymer

Figure 5.2b

(b) Hydrolysis:breaking down a polymer
1 2 3 4

Hydrolysis adds a water molecule, breaking a bond.

1

2

3

The Diversity of Polymers
• Each cell has thousands of different macromolecules • Macromolecules vary among cells of an organism, vary more within a species, and vary even more between species • An immense variety of polymers can be built from a small set of monomers
HO

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Concept 5.2: Carbohydrates serve as fuel and building material
• Carbohydrates include sugars and the polymers of sugars • The simplest carbohydrates are monosaccharides, or single sugars • Carbohydrate macromolecules are polysaccharides, polymers composed of many sugar building blocks

© 2011 Pearson Education, Inc.

Sugars
• Monosaccharides have molecular formulas that areusually multiples of CH2O • Glucose (C6H12O6) is the most common monosaccharide • Monosaccharides are classified by
– The location of the carbonyl group (as aldose or ketose) – The number of carbons in the carbon skeleton

© 2011 Pearson Education, Inc.

Figure 5.3

Aldoses (Aldehyde Sugars)

Ketoses (Ketone Sugars)

Trioses: 3-carbon sugars (C3H6O3)

GlyceraldehydeDihydroxyacetone

Pentoses: 5-carbon sugars (C5H10O5)

Ribose

Ribulose

Hexoses: 6-carbon sugars (C6H12O6)

Glucose

Galactose

Fructose

Figure 5.3a

Aldose (Aldehyde Sugar)

Ketose (Ketone Sugar)

Trioses: 3-carbon sugars (C3H6O3)

Glyceraldehyde

Dihydroxyacetone

Figure 5.3b

Aldose (Aldehyde Sugar)

Ketose (Ketone Sugar)

Pentoses: 5-carbon sugars (C5H10O5)

RiboseRibulose

Figure 5.3c

Aldose (Aldehyde Sugar)

Ketose (Ketone Sugar)

Hexoses: 6-carbon sugars (C6H12O6)

Glucose

Galactose

Fructose

• Though often drawn as linear skeletons, in aqueous solutions many sugars form rings • Monosaccharides serve as a major fuel for cells and as raw material for building molecules

© 2011 Pearson Education, Inc.

Figure 5.4

1 2 3 4 5 6 46 5 1 3 2 4

6 5 1 3 2

(a) Linear and ring forms

6 5 4 3 2 1

(b) Abbreviated ring structure

• A disaccharide is formed when a dehydration reaction joins two monosaccharides • This covalent bond is called a glycosidic linkage

Animation: Disaccharide
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Figure 5.5

1–4 glycosidic 1 linkage 4

Glucose

Glucose

Maltose

(a) Dehydration...