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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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