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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chapter 3Organic
Molecules and Cells
The Diversity of Organic Molecules Makes Life Diverse
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3.1 The chemistry of carbon makes diverse
molecules possible Compounds made of hydrogen and
other elements covalently bonded to carbon atoms
Organisms consist mainly of oxygen, hydrogen, and carbon
Most of the oxygen and hydrogen are in water
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Carbon has unique bonding properties
Carbon can share electrons with as many as four other atoms
Consequently, it can form several different shapes Chains Rings Side branches
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Figure 3.1 Each of these organisms uses a different type of structural carbohydrate
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3.2 Functional groups add to the diversity of organic molecules
A specific combination of bonded atoms that always react in the same way Example: -OH, the hydroxyl group is hydrophilic and
found in alcohol, sugar, and amino acids Isomers – organic molecules with identical
molecular formulas, but a different arrangement of atoms
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Figure 3.2A Functional groups of organic molecules
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3.3 Molecular subunits can be linked to form macromolecules
Carbohydrates, lipids, proteins, and nucleic acids are called macromolecules because of their large size
The largest macromolecules are polymers because they are constructed of many subunits called monomers
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Dehydration and Hydrolysis
Dehydration reaction synthesizes polymers from monomers by removing water
Hydrolysis reaction splits polymers into monomers by adding water
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Figure 3.3B Synthesis and degradation of polymers
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Carbohydrates Are Energy Sources and Structural
Components
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3.4 Simple carbohydrates provide quick energy
Used as an immediate energy source Carbon to hydrogen to oxygen ratio = 1:2:1 Monosaccharides contain a single sugar
molecule Ribose and deoxyribose are found in DNA
Disaccharides contain two monosaccharides joined via dehydration synthesis
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Figure 3.4A Three ways to represent glucose, a source of quick energy for this cheetah and all organisms
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Figure 3.4B Formation and breakdown of maltose, a disaccharide
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3.5 Complex carbohydrates store energy and provide structural support
Polymers of monosaccharides Used for short-term or long-term energy storage
Animals store glucose as glycogen Plants store glucose as starch
Some are used for structure Chitin is used in animals and fungi Cellulose is used by plants
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Figure 3.5 Some of the polysaccharides in plants and animals
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Lipids Provide Storage, Insulation, and Other Functions
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3.6 Fats and oils are rich energy-storage molecules
Hydrophobic biomolecules made of hydrocarbon chains
Fats and oils contain glycerol and fatty acids Sometimes called triglycerides
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Figure 3.6 Formation and breakdown of a fat
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Saturated and Unsaturated Fats
Saturated fats have no double bonds They are saturated with hydrogens
Unsaturated fats have double bonds They are not saturated with hydrogens
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3.7 Other lipids have structural, hormonal, or protective
functions Phospholipids have hydrophobic tails and
hydrophilic heads Found in plasma membranes
Steroids are hydrophobic molecules that pass through plasma membranes
Waxes are hydrophobic molecules used for waterproofing
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Figure 3.7 Phospholipid, cholesterol (a steroid), and wax
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Proteins Have a Wide Variety of Vital Functions
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3.8 Proteins are the most versatile of life’s molecules
Important for structure and function 50% of dry weight of most cells
Several functions Support Metabolism Transport Defense Regulation Motion
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3.9 Each protein is a sequence of particular amino acids
Proteins are macromolecules with amino acid subunits Made of peptide bonds via dehydration synthesis
Polypeptide chain is many amino acids bonded together A protein may have many polypeptide chains
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Figure 3.9A Formation and breakdown of a peptide
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Amino Acids Variety is due to the R group
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Figure 3.9B Amino acid diversity. The amino acids are shown in ionized form
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3.10 The shape of a protein is necessary to its function
Denaturation - the irreversible change of protein shape caused by heat or pH
Levels of Organization
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Figure 3.10 Levels of protein organization
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Nucleic Acids Are Information Molecules
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3.11 The nucleic acids DNA and RNA carry coded information
DNA – deoxyribonucleic acid The genetic material
RNA – ribonucleic acid A copy of DNA used to make proteins
Both are polymers of nucleotides monomers Nucleotides are made of a sugar, a nitrogenous base,
and a phosphate
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Figure 3.11A One nucleotide Figure 3.11B RNA structure 3-35
Figure 3.11C DNA structure at three levels of complexity
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APPLYING THE CONCEPTS—HOW BIOLOGY IMPACTS OUR LIVES
3.12 The Human Genome Project may lead to new
disease treatments Sequenced the genome of humans Scientists create genetic profiles
Used to predict diseases Examples: Type 2 Diabetes, Schizophrenia
Used to make specific treatments
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3.13 The nucleotide ATP is the cell’s energy carrier
Adenosine Triphosphate (ATP) A nucleotide with the base adenine and the
sugar ribose making a compound adenosine Hydrolyzes phosphates to release energy
and form adenosine diphosphate (ADP)
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3-39Figure 3.13B releases energy Animals convert food energy to that of ATP
Figure 3.13A ATP hydrolysis
Connecting the Concepts:Chapter 3
Carbon forms the backbone of carbohydrates, lipids, proteins, and nucleic acids
The macromolecules of cells are polymers of small organic molecules Simple sugars are the monomers of complex
carbohydrates Amino acids are the monomers of proteins Nucleotides are the monomers of nucleic acids Fats are composed of fatty acids and glycerol
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