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Human Biology
 Chapter 2
 Chemistry of living things
 Atoms/Elements
 Bonds
 Water
 pH
 Molecules of life
 Carbohydrates
*Proteins
 Lipids
*Nucleic Acids
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All Matter Consists of Elements Made of
Atoms
 Chemistry
 The study of matter
 Atoms, the smallest functional unit, consist
of
 Protons: positive charge, have mass
 Neutrons: no charge, have mass
 Electrons: negative charge, have no
discernable mass
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Atoms Combine to Form Molecules
 Joining atoms requires energy
 Energy is the capacity to do work
 Stored energy: potential energy
 Energy in motion, doing work: kinetic energy
 Electrons have potential energy
 Shells: the energy levels of electrons
 Orbitals describe the probable location of an
electron
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Three Types of Chemical Bonds
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Table 2.1
Elements of Living Organisms
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Table 2.2
Life Depends on Water
 Water molecules are polar
 Water is liquid at body temperature
 Water can absorb and hold heat energy
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Water Keeps Ions in Solution
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Figure 2.8
The Importance of Hydrogen Ions
 Acids are proton (hydrogen ion) donors
 Bases accept hydrogen ions
 pH Scale
 Hydrogen ion concentration
 Buffers
 Minimize pH change
 Carbonic acid and bicarbonate act as one of
the body’s most important buffer pairs
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The pH Scale
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Figure 2.10
The Organic Molecules of Living Organisms
Carbon, the building block of living things
 Comprises 18% of the body by weight
 Forms four covalent bonds
 Can form single or double bonds
 Can build micro- or macromolecules
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Carbon Can Bond in Many Ways
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Figure 2.12
Making and Breaking Biological
Macromolecules: Dehydration Synthesis and
Hydrolysis
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Figure 2.13
Dehydration Synthesis Is the Reverse of
Hydrolysis
 Dehydration synthesis
 Removes equivalent of a water molecule to
link molecular units
 Requires energy
 Hydrolysis
 Adds the equivalent of a water molecule to
break apart macromolecules
 Releases energy
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Carbohydrates are Composed of
Monosaccharides
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Figure 2.14
Carbohydrates are Used for Energy and
Structural Support
 Oligosaccharides
 Short chains of monosaccharides
 Disaccharides
 Sucrose, fructose, lactose
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Carbohydrates are Used for Energy and
Structural Support
 Polysaccharides: thousands of
monosaccharides joined in chains and
branches
 Starch: made in plants; stores energy
 Glycogen: made in animals; stores energy
 Cellulose: indigestible polysaccharide made
in plants for structural support
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Lipids: Insoluble in Water
 Triglycerides: energy storage molecules
 Fatty acids: saturated and unsaturated
 Phospholipids: cell membranes
 Steroids: carbon-based ring structures
 Cholesterol: used in making estrogen and
testosterone
PLAY
Animation—Lipid Structure and Function
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Proteins: Complex Structures Constructed of
Amino Acids
 Structure
 Primary: amino acid sequence
 Secondary: describes chain’s orientation in
space (e.g., alpha helix, beta sheet)
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Proteins: Complex Structures Constructed of
Amino Acids
 Tertiary: describes three-dimensional
shape created by disulfide and hydrogen
bonds
 Creates polar and nonpolar areas in
molecule
 Quaternary: describes proteins in which
two or more tertiary protein chains are
associated
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Proteins: Complex Structures Constructed of
Amino Acids
 Denaturation
 Permanent disruption of protein structure
 Can be damaged by temperature or
changes in pH
 Leads to loss of biological function
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Enzyme Function
 Enzymes
 Are proteins
 Function as catalysts
 Speed up chemical reactions
 Are not altered or consumed by the
reaction
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Enzyme Function
 The functional shape of an enzyme is
dependent on
 Temperature of reaction medium
 pH
 Ion concentration
 Presence of inhibitors
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Structure and Function of Nucleic Acids
 Functions
 Store genetic information
 Provide information used in making proteins
 Structure
 Nucleotides consist of a phosphate group, a sugar,
and a nitrogenous base
 DNA structure is a double helix: two associated
strands of nucleic acids
 RNA is a single-stranded molecule
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Structure of DNA
 DNA
 Deoxyribonucleic acid
 Double–stranded
 Sugar
 Deoxyribose
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Structure of DNA
 DNA
 Nitrogenous bases
 Adenine
 Thymine
 Cytosine
 Guanine
 Pairing
 Adenine–thymine
 Cytosine–guanine
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Structure of RNA
 RNA
 Ribonucleic acid
 Single–stranded
 Sugar
 Ribose
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Structure of RNA
 RNA
 Nitrogenous bases
 Adenine
 Uracil
 Cytosine
 Guanine
 Pairing
 Adenine–uracil
 Cytosine–guanine
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Structure and Function of Adenosine
Triphosphate (ATP)
 Universal energy source
 Bonds between phosphate groups contain
potential energy
 Breaking the bonds releases energy
 ATP  ADP + P1 + energy
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Structure and Function of Adenosine
Triphosphate (ATP)
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Figure 2.26