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Chapter 3: The Chemical Basis of Life II

Page history last edited by Derek Weber 9 years, 10 months ago

Learning Objectives 

  • Explain the properties of carbon that make it the focal point of organic compounds.
  • Compare and contrast different types of isomeric compounds.
  • List the four major classes of biological macromolecules.
  • Describe each biological macromolecule, and how monomers of each class are brought together to form the macromolecules.
  • Describe the relationship between functional groups and macromolecules.
  • Appreciate the variety and chemical characteristics of common functional groups of organic compounds.
  • Name the different forms of carbohydrate molecules.
  • Relate the structure of polysaccharides to their functions.
  • Understand the structure of triglycerides.
  • Explain how fats function as energy-storage molecules.
  • Apply knowledge of the structure of phospholipids to the formation of membranes.
  • Describe the possible levels of protein structure.
  • Understand the relationship between amino acid sequence and their three-dimensional structure.
  • Give examples of several different proteins and the general types of functions they carry out in a cell.
  • Describe the structure of nucleotides.
  • Compare and contrast the structures of DNA and RNA.
  • Explain the functions of DNA and RNA.


Chapter Summary

Organic molecules are composed of specific functional groups that confer identity, form, and function. Many of these molecules form long-chain polymers of characteristic subunits, constituting the macromolecules upon which life depends. The bonds between subunits are formed by dehydration reactions requiring energy and resulting in the subsequent removal of one molecule of water per bond. The bonds are broken via hydrolysis reactions, releasing energy and requiring the input of water. The four types of macromolecules found within all living organisms are proteins, nucleic acids, lipids, and carbohydrates.


Carbohydrates include the monosaccharides, single subunits that serve as energy storage molecules, the two unit disaccharides that are plant transport molecules, and the polysaccharides, molecules hundreds of glucose units long and insoluble as a result of their coils or branches. Cellulose and chitin are important structural carbohydrates because most organisms lack the means to degrade them.


Lipids comprise the second group of macromolecules, unique in that they are completely insoluble in water. The simplest are the fats, which provide ideal long-term energy reserves due to their numerous C—H bonds. Other lipids are important components of biological membranes and have polar ends that orient toward water and nonpolar tails that orient away from it.


Proteins are a diverse group of macromolecules composed of lengthy chains of amino acid subunits. Each subunit consists of a central carbon attached to four functional groups, three that are constant among all amino acids and a fourth (the R group) that confers identity. Proteins have six levels of organization, all of which ultimately depend, therefore, on the initial amino acid sequence and the identity of each unique R group. Special proteins, chaperonins, act as molecular chaperones to help other proteins fold into their active shape. Denaturation results from changing the environmental conditions surrounding a protein. This adversely affects its biological activity, especially when it is an enzyme.


The nucleic acids, DNA and RNA, are enormously long chains of nucleotides each composed of a five-carbon sugar, a phosphate group, and one of four nitrogenous bases. Specific nucleotide identity is conferred by the base, which may be a purine or a pyrimidine. The complementarity of the nitrogenous bases allows for efficient replication of each strand and enables DNA to exist as a protected double helix. The structure of DNA and RNA differ in the sugars that constitute their backbones and in the chemical composition of one of their pyrimidine bases.


Power Point Presentation

Chapter 3 PowerPoint (.pdf) 


Virtual Lectures 

1.  Section 3.1: The Carbon Atom and the Study of Organic Molecules







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1.  Making and Breaking Down Macromolecules

2.  Functional Groups

3.  Complex Carbohydrates

4.  Phospholipids

5.  Amino Acids

6.  Peptide Bonds

7.  Higher Order Protein Structure

8.  Example of Quaternary Structure 

9.  Nucleotides



1.  Here is a copy of the original investigative article from 1961 demonstrating that protein function is encoded by the primary sequence of amino acids.  The entire reference is: 

Haber , E., and Anfinsen, C.B. 1961. Regeneration   of enzyme activity by air oxidation of reduced subtilisin-modified ribonuclease. Journal of  Biological Chemistry 236:422–424.


2.  Gaming the System: Video Gamers Help Researchers Untangle Protein Folding Problem.  The folding of a protein into its final 3-D structure is essential for the function of all living things.  Scientists are interested in try to determine the secrets of protein folding within the cell.  They have enlisted video gamers to assist in elucidating this issue using a free program called Fold.it.  This is a fascinating read.  If enough people are interested, I thought we can start our own group and see how we stack up against other groups from around the world.  We can maybe devise some extra credit opportunities if need be.


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