Chapter 3 (The Molecular Diversity of Life) Carbon, Dehydration and Hydrolysis

You Must Know The properties of carbon that make it so important. The role of dehydration reactions in the formation of organic compounds and hydrolysis in the digestion of organic compounds.

Importance of Carbon You don’t need to memorize these carbon skeletons.

Valences of the major elements of organic molecules Hydrogen (valence  1) Carbon (valence  4) Nitrogen (valence  3) Oxygen (valence  2)

Critically important molecules of all living things fall into four main classes – Carbohydrates – Nucleic acids – Proteins – Lipids The first three of these can form huge molecules called macromolecules © 2014 Pearson Education, Inc.

Hydrocarbons can undergo reactions that release a large amount of energy. Hydrocarbons

Concept 3.2: Macromolecules are polymers, built from monomers © 2014 Pearson Education, Inc.

A dehydration reaction occurs when two monomers bond together through the loss of a water molecule The Synthesis and Breakdown of Polymers © 2014 Pearson Education, Inc.

Figure 3.6a Unlinked monomer Short polymer Longer polymer (a) Dehydration reaction: synthesizing a polymer Dehydration removes a water molecule, forming a new bond.

Polymers are disassembled to monomers by hydrolysis, a reaction that is essentially the reverse of the dehydration reaction The Synthesis and Breakdown of Polymers © 2014 Pearson Education, Inc.

Figure 3.6b (b) Hydrolysis: breaking down a polymer Hydrolysis adds a water molecule, breaking a bond.

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 © 2014 Pearson Education, Inc.

The Chemical Groups Most Important to Life Functional groups are the components of organic molecules that are most commonly involved in chemical reactions. The number and arrangement of functional groups give each molecule its unique properties. © 2014 Pearson Education, Inc.

Figure 3.5 Chemical Group Hydroxyl group ( OH) Compound Name Examples Alcohol Ketone Aldehyde Methylated compound Organic phosphate Thiol Amine Carboxylic acid, or organic acid Ethanol Acetone Propanal Acetic acid Glycine Cysteine Glycerol phosphate 5-Methyl cytosine Amino group ( NH 2 ) Carboxyl group ( COOH) Sulfhydryl group ( SH) Phosphate group ( OPO 3 2– ) Methyl group ( CH 3 ) Carbonyl group ( C O) The seven functional groups that are most important in the chemistry of life: You need to memorize the chemical groups, but not the compound name or examples.

Figure 3.5aa Hydroxyl group ( OH) Alcohol (The specific name usually ends in -ol.) (may be written HO )

Figure 3.5ab Carbonyl group ( C O)

Figure 3.5ac Carboxyl group ( COOH) Carboxylic acid, or organic acid Acetic acid, which gives vinegar its sour taste Ionized form of COOH (carboxylate ion), found in cells

Figure 3.5ad Amino group ( NH 2 ) Amine Glycine, an amino acid (note its carboxyl group) Ionized form of NH 2 found in cells

Figure 3.5ba Sulfhydryl group ( SH) (may be written HS )

Figure 3.5bb Phosphate group ( OPO 3 2– ) Organic phosphate

Figure 3.5bc Methyl group ( CH 3 ) Methylated compound