The Chemistry of Life:
Organic Compounds
Chapter 3
Learning Objective 1
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What properties make carbon the central
component of organic compounds?
Carbon Atoms
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form four covalent bonds
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single, double, or triple
straight or branched chains
rings
bond with many different elements
Organic Molecules
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Chains
Organic Molecules
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Double bonds
Organic Molecules
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Branched chains
Organic Molecules
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Rings
KEY CONCEPTS
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Carbon atoms join with one another or
other atoms to form large molecules
with a wide variety of shapes
Learning Objective 2
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What is an isomer?
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What are the 3 principal isomer types?
Isomers
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Structural isomers
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different covalent arrangements
Isomers
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Geometric isomers (cis–trans isomers)
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different spatial arrangements
Isomers
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Enantiomers
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mirror images
Learning Objective 3
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What are the major functional groups
present in organic compounds, and their
properties?
Hydrocarbons
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Organic compounds
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carbon and hydrogen only
nonpolar
hydrophobic
Methyl group
Polar and Ionic
Functional Groups
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Partial charges on atoms
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at opposite ends of a bond
interact with one another
hydrophilic
Hydroxyl and carbonyl groups
Acidic and Basic Groups
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Acidic
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release hydrogen ions
become negatively charged
carboxyl and phosphate groups
Basic
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accepts a hydrogen ion
become positively charged
amino group
Functional Groups
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Polar (hydroxyl)
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Acidic (carboxyl)
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Basic (amino)
Table 3-1a, p. 49
Table 3-1b, p. 49
KEY CONCEPTS
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Hydrocarbons
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nonpolar and hydrophobic
Properties depend on functional groups:
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hydroxyl and carbonyl groups (polar)
carboxyl and phosphate groups (acidic)
amino groups (basic)
Learning Objective 4
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What is the relationship between
polymers and macromolecules?
Polymers and Macromolecules
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Polymers
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long chains of monomers
linked through condensation reactions
Macromolecules
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large polymers
polysaccharides, proteins, and DNA
broken down by hydrolysis reactions
Condensation and Hydrolysis
Condensation
Enzyme A
HO
OH HO
Monomer
OH
Monomer
HO
Hydrolysis
Enzyme B
O
OH + H2O
Dimer
Fig. 3-5, p. 50
Learning Objective 5
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Distinguish among monosaccharides,
disaccharides, and polysaccharides
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What is the difference between storage
polysaccharides and structural
polysaccharides?
Carbohydrates
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Ratio
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Monosaccharide
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1carbon: 2 hydrogen: 1 oxygen
simple sugar
glucose, fructose, ribose
Disaccharide
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2 monosaccharides
joined by glycosidic linkage
maltose, sucrose
Fig. 3-6, p. 51
Glyceraldehyde (C3H6O3)
(an aldehyde)
Dihydroxyacetone (C3H6O3)
(a ketone)
(a) Triose sugars (3-carbon sugars)
Fig. 3-6, p. 51
Ribose (C5H10O5)
(the sugar component of RNA)
Deoxyribose (C5H10O4)
(the sugar component of DNA)
(b) Pentose sugars (5-carbon sugars)
Fig. 3-6, p. 51
Glucose (C6H12O6)
(an aldehyde)
Fructose (C6H12O6)
(a ketone)
Galactose (C6H12O6)
(an aldehyde)
(c) Hexose sugars (6-carbon sugars)
Fig. 3-6, p. 51
Polysaccharides
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Long chains
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Storage polysaccharides
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repeating units of simple sugar
starch in plants
glycogen in animals
Structural polysaccharide
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cellulose, cell walls of plants
Polysaccharides
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Starch
KEY CONCEPTS
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Carbohydrates are composed of sugar
subunits (monosaccharides), which can
be joined to form disaccharides, storage
polysaccharides, and structural
polysaccharides
Learning Objective 6
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What are the characteristics,
composition, and biological functions of
fats, phospholipids, and steroids?
Lipids
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Mainly hydrocarbon-containing regions
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few oxygens (polar or ionic groups)
Greasy or oily consistency
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relatively insoluble in water
Fats
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Triacylglycerol
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Monoacylglycerols & diacylglycerols
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main storage fat
glycerol + 3 fatty acids
1 or 2 fatty acids
saturated or unsaturated fatty acid
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hydrogens
Triacylglycerol
Ester linkage
A triacylglycerol
Fig. 3-12b, p. 56
Phospholipids
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Structure
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glycerol
2 fatty acids
phosphate group
Function
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cell membrane component
Phospholipid
Phosphate
group
Glycerol
Choline
Fatty acids
Water
Hydrophilic
head
Hydrophobic
tail
Fig. 3-13, p. 58
Steroids
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Carbon atoms arranged in 4 rings
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cholesterol, bile salts, some hormones
Indicates
double bond
Cholesterol
(a) Cholesterol is an essential component of animal
cell membranes.
Fig. 3-15a, p. 59
KEY CONCEPTS
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Lipids store energy (triacylglycerol) and
are the main structural components of
cell membranes (phospholipids)
Learning Objective 7
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What are the structures and
functions of proteins?
Proteins
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Polypeptides
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long, linear polymers
20 amino acids (monomers)
joined by peptide bonds
Many functions
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enzymes
structural components
cell regulators
Peptide Bonds
R group
Carboxyl Amino
group
group R group
Glycine
Alanine
Peptide bond
Glycylalanine (a dipeptide)
Fig. 3-18, p. 63
Learning Objective 8
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What features are shared by all amino
acids?
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How are amino acids grouped into
classes based on their side chains?
Amino Acids
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Amino group and carboxyl group
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Side chains
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determine chemical properties
nonpolar, polar, acidic, or basic
Dipolar ions at cell pH
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important biological buffers
Dipolar Ions
Learning Objective 9
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What are the four levels of organization
of protein molecules?
Primary Structure
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Linear sequence of amino acids in
polypeptide chain
Secondary Structure
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Regular conformation
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α -helix or β-pleated sheet
hydrogen bonds between amino acids
KEY:
Carbon atom
Oxygen atom
Nitrogen atom
Hydrogen bonds
hold helix coils
in shape
Hydrogen atom
R group
(a) In an α-helix the R groups project out from the sides. (The
R groups have been omitted in the simplified diagram at left.)
Fig. 3-20a, p. 64
Tertiary Structure
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Overall shape of polypeptide chain
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chemical interactions of side chains
Hydrogen
bond
Ionic bond
Disulfide bond
Hydrophobic
interaction
(a) Hydrogen bonds, ionic bonds, hydrophobic interactions,
and disulfide bridges between R groups hold the parts of
the molecule in the designated shape.
Fig. 3-21a, p. 65
Quaternary Structure
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2 or more polypeptide chains
Heme
Beta chain
(β-globin)
Alpha chain
(α-globin)
Alpha chain
(α-globin)
Beta chain
(β-globin)
(a) Hemoglobin, a globular protein, consists
of four polypeptide chains, each joined to an
iron-containing molecule, a heme.
Fig. 3-22a, p. 66
Heme
Beta chain
(β-globin)
Alpha chain
(α-globin)
Alpha chain
(α-globin)
Stepped Art
Beta chain
(β-globin)
Fig. 3-22a, p. 66
KEY CONCEPTS
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Proteins have multiple levels of
structure and are composed of amino
acid subunits joined by peptide bonds
Learning Objective 10
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What are the components of a nucleotide?
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Name some nucleic acids and
nucleotides, and discuss their importance
in living organisms
Nucleotides
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Nitrogenous base
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Five-carbon sugar
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2-ring purine or 1-ring pyrimidine
ribose or deoxyribose
One or more phosphate groups
Purines and Pyrimidines
Cytosine (C)
Thymine (T)
Uracil (U)
(a) Pyrimidines. The three major pyrimidine bases found in
nucleotides are cytosine, thymine (in DNA only), and uracil
(in RNA only).
Fig. 3-23a, p. 68
Adenine (A)
Guanine (G)
(b) Purines. The two major purine bases found in nucleotides
are adenine and guanine.
Fig. 3-23b, p. 68
Nucleic Acids
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DNA and RNA
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long chains of nucleotides
Store and transfer information
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sequence of amino acids in proteins
structure and function of the organism
Nucleic Acid
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RNA
Nucleotide
Ribose
Uracil
Ribose
Adenine
Phosphodiester
linkage
Ribose
Ribose
Cytosine
Guanine
Fig. 3-24, p. 68
Nucleotides
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ATP (adenosine triphosphate)
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essential in energy metabolism
NAD+
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electron acceptor in biological oxidation
and reduction reactions
Nucleotides
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cAMP
KEY CONCEPTS
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Nucleic acids (DNA and RNA) are
informational molecules composed of
long chains of nucleotide subunits. ATP
and some other nucleotides have a
central role in energy metabolism
Learning Objective 11
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Review the functions and chemical
compositions of the 4 major groups of
organic compounds: carbohydrates,
lipids, proteins, and nucleic acids
Structure of a Phospholipid
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Condensation and Hydrolysis
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Secondary and Tertiary
Structure
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Structure of Starch and
Cellulose
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Triglyceride Formation
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