The Structure and Function of Large Biological Molecules

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Each polypeptide has a unique linear sequence of amino acids

Slide 67

Peptide

bond

Fig. 5-18

Amino end

(N-terminus)

Peptide

bond

Side chains

Backbone

Carboxyl end

(C-terminus)

(a)

(b)

Slide 68

Protein Structure and Function

A functional protein consists of one or more polypeptides twisted, folded, and coiled into a unique shape

Slide 69

Fig. 5-19

A ribbon model of lysozyme

(a)

(b)

A space-filling model of lysozyme

Groove

Groove

Slide 70

Fig. 5-19a

A ribbon model of lysozyme

(a)

Groove

Slide 71

Fig. 5-19b

(b)

A space-filling model of lysozyme

Groove

Slide 72

The sequence of amino acids determines a protein’s three-dimensional structure

A protein’s structure determines its function

Slide 73

Fig. 5-20

Antibody protein

Protein from flu virus

Slide 74

Four Levels of Protein Structure

The primary structure of a protein is its unique sequence of amino acids

Secondary structure, found in most proteins, consists of coils and folds in the polypeptide chain

Tertiary structure is determined by interactions among various side chains (R groups)

Quaternary structure results when a protein consists of multiple polypeptide chains

Animation: Protein Structure Introduction

Slide 75

Primary structure, the sequence of amino acids in a protein, is like the order of letters in a long word

Primary structure is determined by inherited genetic information

Animation: Primary Protein Structure

Slide 76

Fig. 5-21

Primary

Structure

Secondary

Structure

Tertiary

Structure

 pleated sheet

Examples of

amino acid

subunits

+H3N

Amino end

 helix

Quaternary

Structure

Slide 77

Fig. 5-21a

Amino acid

subunits

+H3N

Amino end

25

20

15

10

5

1

Primary Structure

Slide 78