台湾清华大学生命科学第六讲(焦传金教授)

Chapter 5

The Structure and Function of Large Biological MoleculesPowerPoint® Lecture Presentations for

BiologyEighth Edition Neil Campbell and Jane ReeceLectures by Chris Romero, updated by Erin Barley with contributions from Joan SharpCopyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

台湾清华大学生命科学第六讲(焦传金教授)

Overview: The Molecules of Life

All living things are made up of four classes of large biological molecules: carbohydrates, lipids, proteins, and nucleic acids Within cells, small organic molecules are joined together to form larger molecules Macromolecules are large molecules composed of thousands of covalently connected atoms

Molecular structure and function are inseparableCopyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

台湾清华大学生命科学第六讲(焦传金教授)

Fig. 5-1

Why do scientists study the structures of macromolecules?

台湾清华大学生命科学第六讲(焦传金教授)

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 called monomers

Three of the four classes of life’s organic molecules are polymers:– Carbohydrates – Proteins – Nucleic acidsCopyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

台湾清华大学生命科学第六讲(焦传金教授)

The Synthesis and Breakdown of Polymers

A condensation reaction or more specifically a dehydration reaction occurs when two monomers bond together through the loss of a water molecule Enzymes are macromolecules that speed up the dehydration process Polymers are disassembled to monomers by hydrolysis, a reaction that is essentially the reverse of the dehydration reactionCopyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

台湾清华大学生命科学第六讲(焦传金教授)

Fig. 5-2

HO

1

2 Short polymer

3

H

HO

H

Unlinked monomer

Dehydration removes a water molecule, forming a new bond

H2O

HO

1

2

3

4

H

The synthesis and breakdown of polymers

Longer polymer

(a) Dehydration reaction in the synthesis of a polymer

HO

1

2

3

4

H

Hydrolysis adds a water molecule, breaking a bond

H2O

HO

1

2

3

H

HO

H

(b) Hydrolysis of a polymer

台湾清华大学生命科学第六讲(焦传金教授)

The Diversity of Polymers Each cell has thousands of different kinds of macromolecules2 3H HO

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

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

台湾清华大学生命科学第六讲(焦传金教授)

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

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

台湾清华大学生命科学第六讲(焦传金教授)

Sugars Monosaccharides have molecular formulas that are usually multiples of CH2O Glu

cose (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 skeletonCopyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

台湾清华大学生命科学第六讲(焦传金教授)

Fig. 5-3 Trioses (C3H6O3) Pentoses (C5H10O5) Hexoses (C6H12O6)

Glyceraldehyde

Ribose Glucose Galactose

Dihydroxyacetone

Ribulose Fructose

台湾清华大学生命科学第六讲(焦传金教授)

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

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

台湾清华大学生命科学第六讲(焦传金教授)

Fig. 5-4

Linear and ring forms of glucose

(a) Linear and ring forms

(b) Abbreviated ring structure

台湾清华大学生命科学第六讲(焦传金教授)

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

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

台湾清华大学生命科学第六讲(焦传金教授)

Fig. 5-5

Examples of disaccharide synthesis1–4 glycosidic linkage

Glucose

Glucose

Maltose1–2 glycosidic linkage

(a) Dehydration reaction in the synthesis of maltose

Glucose

Fructose

Sucrose

(b) Dehydration reaction in the synthesis of sucrose

台湾清华大学生命科学第六讲(焦传金教授)

Polysaccharides Polysaccharides, the polymers of sugars, have storage and structural roles The structure and function of a polysaccharide are determined by its sugar monomers and the positions of glycosidic linkages

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

台湾清华大学生命科学第六讲(焦传金教授)

Storage Polysaccharides Starch, a storage polysaccharide of plants, consists entirely of glucose monomers Plants store surplus starch as granules within chloroplasts and other plastids

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings