CHAPTER 3

The Molecules of Life

• Americans consume an average of 140 pounds of sugar per person per year

• A typical cell in your body has about 2 meters of DNA

Biochemistry

• Inorganic compounds: are compounds that do not contain both carbon and hydrogen

Water (H₂O), salt (NaCl), acids (HCl),

bases (NaOH), etc

• Organic compounds: Contain carbon and hydrogen

– Proteins, lipids, hydrocarbons, etc. Often are large complex molecules

ORGANIC MOLECULES

• A cell is mostly water

• Carbon can use its bonds to

• The simplest organic compounds are hydrocarbons

• Larger hydrocarbons

• Each type of organic molecule has a unique three-dimensional shape that defines its function in an organism

• The unique properties of an organic compound depend not only on its carbon skeleton but also on the atoms attached to the skeleton

• Some common functional groups

Giant Molecules from Smaller Building Blocks

• On a molecular scale, many of life’s molecules are gigantic

• Most macromolecules are polymers

• Organisms also have to break down macromolecules

BIOLOGICAL MOLECULES

• There are four categories of large molecules in cells

Carbohydrates

• Carbohydrates include

Monosaccharides

• Monosaccharides are simple sugars

• The monosaccharides glucose and fructose are isomers

• In aqueous solutions, monosaccharides form rings

Disaccharides

• A disaccharide is a double sugar

• Disaccharides are joined by the process of dehydration synthesis

• The most common disaccharide is sucrose, common table sugar

• The United States is one of the world’s leading markets for sweeteners

Polysaccharides

• Complex carbohydrates are called polysaccharides

• Polysaccharides

• One familiar example of a polysaccharide is starch

• Animals store excess sugar in the form of a polysaccharide called glycogen

• Cellulose is the most abundant organic compound on Earth

• Most animals cannot derive nutrition from fiber

Lipids

• Lipids are hydrophobic

Fats

• Dietary fat consists largely of the molecule triglyceride

• Fats perform essential functions in the human body

• Unsaturated fatty acids

• Most animal fats have a high proportion of saturated fatty acids

Steroids

• Steroids are very different from fats in structure and function

• Synthetic anabolic steroids are controversial

Proteins

• A protein is a polymer constructed from amino acid monomers

• The four types of proteins

The Monomers: Amino Acids

• All proteins are constructed from a common set of 20 kinds of amino acids

Proteins as Polymers

• Cells link amino acids together by dehydration synthesis

• Your body has tens of thousands of different kinds of protein

• Primary structure

• A slight change in the primary structure of a protein affects its ability to function

Protein Shape

• Proteins have four levels of structure

What Determines Protein Structure?

• A protein’s shape is sensitive to the surrounding environment

Nucleic Acids

• Nucleic acids are information storage molecules

• There are two types of nucleic acids

• Nucleic acids are polymers of nucleotides

SUMMARY OF KEY CONCEPTS

• Giant Molecules from Smaller Building Blocks

• Biological Molecules