CHAPTER 3
The
Molecules of Life
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Americans consume an average of 140 pounds of sugar per
person per year
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A typical cell in your body has about 2 meters of DNA
Biochemistry
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Inorganic compounds:
are compounds that do not contain both carbon and hydrogen
Water (H2O), salt
(NaCl), acids (HCl),
bases (NaOH), etc
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Organic compounds:
Contain carbon and hydrogen
–
Proteins, lipids, hydrocarbons, etc. Often are large complex molecules
ORGANIC MOLECULES
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A cell is mostly water
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Carbon can use its bonds to
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The simplest organic compounds are hydrocarbons
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Larger hydrocarbons
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Each type of organic molecule has a unique
three-dimensional shape that defines its function in an organism
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The unique properties of an organic compound depend not
only on its carbon skeleton but also on the atoms attached to the skeleton
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Some common functional groups
Giant Molecules from Smaller
Building Blocks
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On a molecular scale, many of life’s molecules are gigantic
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Most macromolecules are polymers
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Organisms also have to break down macromolecules
BIOLOGICAL MOLECULES
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There are four categories of large molecules in cells
Carbohydrates
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Carbohydrates include
Monosaccharides
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Monosaccharides are simple sugars
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The monosaccharides glucose and fructose are isomers
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In aqueous solutions, monosaccharides form rings
Disaccharides
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A disaccharide is a double sugar
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Disaccharides are joined by the process of dehydration
synthesis
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The most common disaccharide is sucrose, common table
sugar
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The United States
is one of the world’s leading markets for sweeteners
Polysaccharides
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Complex carbohydrates are called polysaccharides
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Polysaccharides
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One familiar example of a polysaccharide is starch
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Animals store excess sugar in the form of a
polysaccharide called glycogen
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Cellulose is the most abundant organic compound on
Earth
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Most animals cannot derive nutrition from fiber
Lipids
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Lipids are hydrophobic
Fats
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Dietary fat consists largely of the molecule
triglyceride
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Fats perform essential functions in the human body
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Unsaturated fatty acids
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Most animal fats have a high proportion of saturated
fatty acids
Steroids
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Steroids are very different from fats in structure and
function
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Synthetic anabolic steroids are controversial
Proteins
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A protein is a polymer constructed from amino acid
monomers
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The four types of proteins
The Monomers: Amino Acids
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All proteins are constructed from a common set of 20
kinds of amino acids
Proteins as Polymers
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Cells link amino acids together by dehydration
synthesis
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Your body has tens of thousands of different kinds of
protein
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Primary structure
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A slight change in the primary structure of a protein
affects its ability to function
Protein Shape
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Proteins have four levels of structure
What Determines Protein
Structure?
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A protein’s shape is sensitive to the surrounding
environment
Nucleic Acids
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Nucleic acids are information storage molecules
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There are two types of nucleic acids
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Nucleic acids are polymers of nucleotides
SUMMARY OF KEY CONCEPTS
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Giant Molecules from Smaller Building Blocks
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Biological Molecules