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Chemistry Comes Alive
Part B
Human Anatomy & Physiology, Sixth Edition
Elaine N. Marieb
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
2
Biochemistry
 Organic compounds
 Contain carbon, are covalently bonded, and are
often large
 Inorganic compounds
 Do not contain carbon
 Water, salts, and many acids and bases
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Properties of Water
 High heat capacity – absorbs and releases large
amounts of heat before changing temperature
 High heat of vaporization – changing from a liquid to
a gas requires large amounts of heat
 Polar solvent properties – dissolves ionic substances,
forms hydration layers around large charged
molecules, and serves as the body’s major transport
medium
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Properties of Water
 Reactivity – is an important part of hydrolysis and
dehydration synthesis reactions
 Cushioning – resilient cushion around certain body
organs
PLAY
InterActive Physiology®:
Fluid, Electrolyte, and Acid/Base Balance: Introduction to Body Fluids
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Salts
 Inorganic compounds
 Contain cations other than H+ and anions other than
OH–
 Are electrolytes; they conduct electrical currents
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Acids and Bases
 Acids release H+ and are therefore proton donors
HCl  H+ + Cl –
 Bases release OH– and are proton acceptors
NaOH  Na+ + OH–
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Acid-Base Concentration (pH)
 Acidic solutions have higher H+ concentration and
therefore a lower pH
 Alkaline solutions have lower H+ concentration and
therefore a higher pH
 Neutral solutions have equal H+ and OH–
concentrations
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Acid-Base Concentration (pH)
 Acidic: pH 0–6.99
 Basic: pH 7.01–14
 Neutral: pH 7.00
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Figure 2.12
Buffers
 Systems that resist abrupt and large swings in the pH
of body fluids
 Carbonic acid-bicarbonate system
 Carbonic acid dissociates, reversibly releasing
bicarbonate ions and protons
 The chemical equilibrium between carbonic acid
and bicarbonate resists pH changes in the blood
PLAY
InterActive Physiology®:
Fluid, Electrolyte, and Acid/Base Balance: Acid/Base Homeostasis
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Organic Compounds
 Molecules unique to living systems contain carbon
and hence are organic compounds
 They include:
 Carbohydrates
 Lipids
 Proteins
 Nucleic Acids
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Carbohydrates
 Contain carbon, hydrogen, and oxygen
 Their major function is to supply a source of cellular
food
 Examples:
 Monosaccharides or simple sugars
Figure 2.13a
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Carbohydrates
 Disaccharides or double sugars
Figure 2.13b
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Carbohydrates
 Polysaccharides or polymers of simple sugars
Figure 2.13c
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Lipids
 Contain C, H, and O, but the proportion of oxygen
in lipids is less than in carbohydrates
 Examples:
 Neutral fats or triglycerides
 Phospholipids
 Steroids
 Eicosanoids
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Neutral Fats (Triglycerides)
 Composed of three fatty acids bonded to a glycerol
molecule
Figure 2.14a
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Other Lipids
 Phospholipids – modified triglycerides with two
fatty acid groups and a phosphorus group
Figure 2.14b
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Other Lipids
 Steroids – flat molecules with four interlocking hydrocarbon rings
 Eicosanoids – 20-carbon fatty acids found in cell membranes
Figure 2.14c
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Representative Lipids Found in the Body
 Neutral fats – found in subcutaneous tissue and around
organs
 Phospholipids – chief component of cell membranes
 Steroids – cholesterol, bile salts, vitamin D, sex
hormones, and adrenal cortical hormones
 Fat-soluble vitamins – vitamins A, E, and K
 Eicosanoids – prostaglandins, leukotriens, and
thromboxanes
 Lipoproteins – transport fatty acids and cholesterol in
the bloodstream
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Amino Acids
 Building blocks of protein, containing an amino
group and a carboxyl group
 Amino acid structure
PLAY
InterActive Physiology®:
Fluid, Electrolyte, and Acid/Base Balance: Introduction to Body Fluids
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Amino Acids
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Figure 2.15a-c
Amino Acids
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Figure 2.15d, e
Protein
 Macromolecules composed of combinations of 20
types of amino acids bound together with peptide
bonds
Figure 2.16
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Structural Levels of Proteins
 Primary – amino acid sequence
 Secondary – alpha helices or beta pleated sheets
PLAY
Chemistry of Life:
Proteins: Secondary Structure
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Structural Levels of Proteins
 Tertiary – superimposed folding of secondary
structures
 Quaternary – polypeptide chains linked together in a
specific manner
PLAY
Chemistry of Life:
Proteins: Tertiary Structure
PLAY
Chemistry of Life:
Proteins: Quaternary Structure
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Structural Levels of Proteins
Figure 2.17a-c
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Structural Levels of Proteins
Figure 2.17d, e
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Fibrous and Globular Proteins
 Fibrous proteins
 Extended and strandlike proteins
 Examples: keratin, elastin, collagen, and certain
contractile fibers
 Globular proteins
 Compact, spherical proteins with tertiary and
quaternary structures
 Examples: antibodies, hormones, and enzymes
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Protein Denuaturation
 Reversible
unfolding of
proteins due to
drops in pH
and/or increased
temperature
Figure 2.18a
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Protein Denuaturation
 Irreversibly denatured proteins cannot refold and
are formed by extreme pH or temperature changes
Figure 2.18b
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Molecular Chaperones (Chaperonins)
 Help other proteins to achieve their functional threedimensional shape
 Maintain folding integrity
 Assist in translocation of proteins across membranes
 Promote the breakdown of damaged or denatured
proteins
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Characteristics of Enzymes
 Most are globular proteins that act as biological
catalysts
 Holoenzymes consist of an apoenzyme (protein) and
a cofactor (usually an ion)
 Enzymes are chemically specific
 Frequently named for the type of reaction they
catalyze
 Enzyme names usually end in -ase
 Lower activation energy
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Characteristics of Enzymes
Figure 2.19
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Mechanism of Enzyme Action
 Enzyme binds with substrate
 Product is formed at a lower activation energy
 Product is released
PLAY
How Enzymes Work
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Mechanism of Enzyme Action
Active site
Amino acids
1
Enzyme (E)
Substrates (s)
H20
Enzymesubstrate
complex (E–S)
2
Free enzyme (E)
3
Peptide bond
Internal rearrangements
leading to catalysis
Dipeptide product (P)
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Figure 2.20
Nucleic Acids
 Composed of carbon, oxygen, hydrogen, nitrogen,
and phosphorus
 Their structural unit, the nucleotide, is composed of
N-containing base, a pentose sugar, and a phosphate
group
 Five nitrogen bases contribute to nucleotide
structure – adenine (A), guanine (G), cytosine (C),
thymine (T), and uracil (U)
 Two major classes – DNA and RNA
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Deoxyribonucleic Acid (DNA)
 Double-stranded helical molecule found in the
nucleus of the cell
 Replicates itself before the cell divides, ensuring
genetic continuity
 Provides instructions for protein synthesis
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Structure of DNA
Figure 2.21a
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Structure of DNA
Figure 2.21b
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Ribonucleic Acid (RNA)
 Single-stranded molecule found in both the nucleus
and the cytoplasm of a cell
 Uses the nitrogenous base uracil instead of thymine
 Three varieties of RNA: messenger RNA, transfer
RNA, and ribosomal RNA
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Adenosine Triphosphate (ATP)
 Source of immediately usable energy for the cell
 Adenine-containing RNA nucleotide with three
phosphate groups
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Adenosine Triphosphate (ATP)
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Figure 2.22
How ATP Drives Cellular Work
Figure 2.23
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