BASIC CHEMISTRY

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BASIC CHEMISTRY
2
WHAT WILL WE COVER?

• Matter, elements, and atoms
• Atomic structure
• Chemical bonds
• Chemistry of water
• Acids, bases, and pH
• Macromolecule structure and function

3
MATTER

• Matter is defined as anything possessing mass and
  taking up space
• Tangible
• Can exist in various forms
• Solid
• Liquid
• Gas
• Comprised of many elements

4
ELEMENTS

• An element cannot be broken down into simpler
  substances by normal chemical means
• Approximately 100 different elements exist
• Each is denoted by a symbol
• e.g., Carbon (C), hydrogen (H), etc.
• e.g., NOT water (H2O), glucose, etc.

X
Chlorine (Cl)
Sodium Chloride (NaCl)
Sodium (Na)
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ELEMENTS

• About 25 elements are known to be essential to
  life
• 96 of the mass of living things is comprised
  of just four elements
• Carbon (C)
• Hydrogen (H)
• Nitrogen (N)
• Oxygen (O)

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ATOMS

• An atom is the smallest unit into which an
  element can be subdivided while retaining its
  properties
• Comprised of smaller subatomic particles
• Protons charge mass 1 amu
• Neutrons no charge mass 1 amu
• Electrons - charge mass ltltlt 1 amu
• (1 atomic mass unit (amu) 1 Dalton 1.7
  10-24 g)

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ATOMIC STRUCTURE

• Protons and neutrons form an atoms nucleus
• Electrons are present outside of the nucleus

Helium (He) atom
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ATOMIC NUMBER

• Atoms of different elements possess different
  numbers of protons
• The number of protons in an atom is termed its
  atomic number
• This number defines the element

1
2
3
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ATOMIC MASS

• Protons and neutrons have significant mass
• The number of protons plus neutrons in an atom is
  termed its atomic mass
• Electrons have negligible mass
• This number is slightly variable for many elements

1
4
7
H
Li
He
1
2
3
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ISOTOPES

• Isotopes are atoms of the same element possessing
  different atomic masses
• Due to different numbers of neutrons
• Identical chemical behavior

1
2
3
H
H
H
1
1
1
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ISOTOPES

• Some isotopes are stable
• e.g., 1H, 2H, 12C, 13C, etc.
• Some isotopes are unstable
• e.g., 3H, 14C, 32P, 35S, etc.
• Radioactive

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ISOTOPES

• Radioactive isotopes
• Decay at a constant rate into more stable forms
• May decay into another element
• e.g., 14C ? N
• Various uses
• Important research tools
• Monitor biological processes
• Diagnostic tools in medicine
• Determine age of fossils
• Sometimes produce superheroes

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ISOTOPES

• Each radioactive isotope has a fixed rate of
  decay
• Unaffected by temperature, pressure etc.
• The time required for half of a sample to decay
  is termed the radioisotopes half-life
• e.g., Half-life of 14C is 5,730 years

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ISOTOPES

• Fossils contain isotopes of elements that
  accumulated while they were alive
• Accumulation stops upon death
• Death tends to reduce ones appetite
• Accumulated isotopes slowly decay into more
  stable isotopes

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ISOTOPES

• Ages of fossils can be determined using
  radiometric dating
• Compares accumulating daughter isotope to
  remaining parent isotope
• e.g., Carbon dating is useful for dating fossils
  up to 75,000 years old
• 13 half-lives
• Radioisotopes with longer half-lives can be
  used to date older fossils

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ELECTRON SHELLS

• Electrons vary in the amount of energy they
  possess
• Each electron exists within a discrete energy
  level
• These energy levels are represented by electron
  shells
• Most atoms possess multiple electron shells

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ELECTRON SHELLS

• Electrons exist within electron shells
• The first shell must be completely filled before
  electrons are placed in the second shell, etc.
• The first shell can hold 2 electrons
• The next few electrons can each hold 8 electrons

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CHEMICAL BONDS

• Atoms are most stable when their outermost
  electron shell is completely full
• Making and breaking chemical bonds involves the
  exchange or rearrangement of electrons
• Atoms will tend to react such that their
  outermost electron shell becomes completely full

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CHEMICAL BONDS

• How would you expect F and Cl to react?
• Li and Na?
• He, Ne, and Ar?

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IONS

• A sodium atom possesses a single electron in its
  outermost electron shell
• Tends to lose this electron
• Loss of the electron produces a sodium ion
• A charged form of a sodium atom

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IONS

• A chlorine atom possesses seven electrons in its
  outermost electron shell
• Tends to gain a single electron
• Gain of this electron produces a chloride ion
• A charged form of a chlorine atom

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IONIC BONDS

• The attraction between oppositely charged ions is
  termed an ionic bond
• Compounds formed by ionic bonds are called ionic
  compounds or salts
• Indefinite size and number of ions
• Ions present in a fixed ratio
• e.g., 11 ratio in NaCl

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COVALENT BONDS

• Electrons are not always gained or lost
• Molecules can be formed when electrons are shared
• Sharing is always in pair(s) of electrons
• Shared electrons contribute to electron shells of
  both atoms
• This sharing of electrons is termed a covalent
  bond

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COVALENT BONDS

• The sharing of a pair of electrons forms a
  covalent bond
• A double covalent bond involves the sharing of
  two pairs of electrons
• A triple covalent bond involves the sharing of
  three pairs of electrons

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COVALENT BONDS

• Electron sharing can be equal or unequal
• Equal sharing results in no separation of charges
• Nonpolar covalent bonds

Methane
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COVALENT BONDS

• Electron sharing can be equal or unequal
• Unequal sharing results in a separation of
  charges
• Polar covalent bonds
• Electronegative atoms such as oxygen and nitrogen
  tend to attract electrons more strongly than
  carbon or hydrogen
• They thereby possess partial negative charges

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COVALENT BONDS

• Water is a polar molecule
• The hydrogen atoms possess partial positive
  charges
• The oxygen atom possesses a partial negative
  charge

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HYDROGEN BONDS

• Attraction between a hydrogen atom bearing a
  partial positive charge and another atom bearing
  a partial negative charge
• Much weaker than covalent or ionic bonds
• 1/20 as strong
• Many weak bonds can add up to a significant
  force
• Transient
• Constantly breaking and reforming

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CHEMISTRY OF WATER

• Water is a critically important molecule
• Most of the Earths surface is submerged in water
• Life on Earth began in water
• Life evolved in water for 3 billion years
  before spreading onto land
• The abundance of water is a major reason why
  the Earth is habitable

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CHEMISTRY OF WATER

• Water is the most prevalent molecule within
  living organisms
• Cells are about 70 95 water
• Most cells are themselves surrounded by water

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CHEMISTRY OF WATER

• Water molecules possess polar covalent bonds
• Able to participate in H-bonds
• Water molecules interact with each other
• Water is held together by these H-bonds
• Cohesion
• Water attaches to other ions and molecules
• Adhesion

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CHEMISTRY OF WATER

• Cohesion and adhesion allow transport of water
  against gravity
• Fluid movement into capillary tubes or xylem
  vessels
• Capillary action

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CHEMISTRY OF WATER

• Surface tension results from cohesion
• Difficult to break the surface of water
• e.g., Water strider, skipping rocks, etc.

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WATER AS A SOLVENT

• Water is a powerful and versatile solvent
• A wide variety of molecules and ions dissolve in
  water
• e.g., Sugars, salts, some proteins, etc.
• Interacts well with polar or charged molecules
  and ions
• Most chemical reactions within organisms occur in
  a water medium

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WATER AS A SOLVENT

• Polar or charged molecules and ions are
  hydrophilic
• Interact favorably with water
• Hydration shells surround ions from salts
• Similar structures surround polar molecules

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WATER AS A SOLVENT

• Many molecules and ions dissolve in water
• A solution is formed
• Water is the solvent
• The salt, sugar, dye, etc. is the solute
• A solution in which water is the solvent is
  termed an aqueous solution

Chicago River before St. Patrick's Day
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WATER AS A SOLVENT

• Not all hydrophilic molecules dissolve in water
• Typical of very large hydrophilic molecules
• e.g., Cotton consists of very large molecules of
  cellulose
• A towel dries your body, but does not dissolve in
  the water

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DISSOCIATION OF WATER

• Most water molecules exist as H2O (H-O-H)
• A small fraction of water molecules exist in a
  dissociated state
• 1 in 554 million molecules in pure water
• A hydrogen atom shifts from one water molecule to
  another
• H-O-H ? H OH- (hydrogen ion hydroxide ion)
• 2H2O ? H3O OH- (hydronium ion hydroxide ion)

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DISSOCIATION OF WATER

• H and OH- are formed when H2O dissociates
• Very reactive
• Equal concentrations in pure water
• 10-7 mol/L
• Concentrations are not always equal
• Can be altered by the addition of acids or bases
• As H ?, OH- ?, and vice versa

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ACIDS, BASES, AND pH

• An acid is a substance that increases the H
  concentration of a solution
• Generally donates additional H
• e.g., HCl ? H Cl-
• A base is a substance that decreases the H
  concentration of a solution
• Either absorbs H or donates OH-
• e.g., NH3 H ? NH4
• e.g., NaOH ? Na OH-

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ACIDS, BASES, AND pH

• pH is a quantitative measure of H
• Pure water is pH 7 (neutral)
• Equal concentrations of H and OH-
• Acidic solution contain more H than OH-
• pH lt 7
• Basic solutions contain more OH- than H
• pH gt 7

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ACIDS, BASES, AND pH

• pH is a quantitative measure of H
• Ranges from 0 (most acidic) to 14 (most basic)
• Each pH unit represents a tenfold change in the
  concentration of H
• e.g., pH 4 has 100 times more H than pH 6

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ACIDS, BASES, AND pH

• The interior pH of most cells is close to 7
• Even slight changes in pH can be harmful to cells
  and organisms
• Chemical processes of the cell are very sensitive
  to concentrations of H and OH-
• The shapes of biological molecules can be altered
  by changes in H and OH- concentrations
• e.g., Enzymes, etc.
• Altered shape can reduce function
• Biological fluids contain buffers
• Substances or systems that minimize changes in pH
  by accepting or donating H

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ACID PRECIPITATION

• Acid precipitation represents a serious assault
  on water quality
• Uncontaminated rain has a pH of about 5.6
• Slightly acidic due to carbonic acid formed from
  dissolved CO2
• CO2 H2O ? H2CO3 ? H HCO3-
• Acid precipitation is more acidic than this
• pH 4.3 rain has been measured in the U.S.
• 20 times more acidic than normal rain

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ACID PRECIPITATION

• Acid precipitation
• Caused primarily by the presence in the
  atmosphere of sulfur oxides and nitrogen oxides
• React with water to form strong acids
• Fall to earth with rain or snow

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ACID PRECIPITATION

• Acid precipitation
• The burning of fossil fuels in factories and
  automobiles is a major source of acid
  precipitation
• Electrical power plants burning coal produce more
  of these pollutants than any other source
• Winds carry these pollutants away
• Acid rain may fall far from industrial centers

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ACID PRECIPITATION

• Acid precipitation
• Can damage life in lakes and streams
• Can remove mineral ions from soil
• e.g., Calcium and magnesium ions
• Essential nutrients
• Ordinarily help to buffer soil
• Can increase the solubility of certain ions
• e.g., Aluminum can reach toxic concentrations

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BIOLOGICAL MACROMOLECULES
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CELL COMPOSITION

• Cell composition
• 70 95 water
• Most of the remainder of the cell is composed of
  organic molecules
• Molecules containing both carbon (C) and
  hydrogen (H)

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MACROMOLECULES

• There are four major classes of large biological
  molecules
• Carbohydrates
• Lipids
• Nucleic acids
• Proteins

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MACROMOLECULES

• Three of the four classes of macromolecules are
  polymers
• Long molecules assembled from many similar or
  identical monomers

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MACROMOLECULES

• Monomers are covalently linked via condensation
  reactions
• a.k.a. Dehydration reactions
• Two monomers are covalently linked to each other
  through the loss of a water molecule
• -H is removed from one monomer
• -OH is removed from the other monomer
• H2O is formed

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MACROMOLECULES

• Polymers can be disassembled into monomers via
  hydrolysis reactions
• Essentially a condensation reaction in reverse
• Covalent bond between monomers is broken through
  the addition of water
• -H is added to one monomer
• -OH is added to the other monomer

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MACROMOLECULES
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CARBOHYDRATES

• Sugars and their polymers
• General formula (CH2O)n
• CHO ratio 121
• Possess numerous polar covalent bonds
• Form H-bonds
• Interact favorably with water
• Hydrophilic

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ROLES OF CARBOHYDRATES

• Key roles of carbohydrates
• Short-term energy storage
• Longer-term energy storage
• Structural roles
• Cell communication

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ROLES OF CARBOHYDRATES

• Short-term energy storage
• Monosaccharides (simple sugars) are the
  simplest carbohydrates
• e.g., Glucose, fructose, galactose, ribose, etc.
• Readily burned to release energy

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ROLES OF CARBOHYDRATES

• Short-term energy storage
• Disaccharides consists of two covalently linked
  monosaccharides
• e.g., Sucrose, lactose, maltose, etc.
• Readily hydrolyzed to form monosaccharides

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LACTOSE INTOLERANCE

• Virtually all humans can digest lactose during
  infancy and early childhood
• Milk is an important food source early in life
• Infants produce the enzyme lactase
• Hydrolyzes lactose into the monosaccharides
  glucose and galactose

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LACTOSE INTOLERANCE

• Production of insufficient amounts of lactase
  results in lactose intolerance
• Lactose intolerance is due to lactase
  insufficiency
• Various symptoms
• Nausea, cramps, bloating, gas, diarrhea, etc.

X
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LACTOSE INTOLERANCE

• Lactose intolerance is the normal situation for
  adult humans
• Lactase production generally begins to decline at
  about age 2
• Lactase production generally halts by about age 4
• Similar declines seen in other mammals
• Such individuals become lactose intolerant

X
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LACTOSE INTOLERANCE

• The frequency of lactose intolerance varies
  widely throughout the world
• Over 90 of humans overall
• 4 of Swedes
• 100 of individuals from certain African and
  Asian populations
• Why do these rates differ so widely?

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LACTOSE INTOLERANCE

• Domestication of plants and animals began rather
  recently
• Sheep, cattle, wheat, and barley were
  domesticated slightly over 10,000 years ago in
  the Near East
• Profoundly altered the way people lived
• Populations settled down and cultivated their
  own food
• Populations began to grow
• Cattle, sheep, grains, and lifestyle reached
  Western Europe a few millennia later

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LACTOSE INTOLERANCE

• Mutations causing lactase to be produced
  throughout adult life occurred in Western Europe
• This mutation was beneficial in populations
  involved in intensive dairy farming
• Natural selection increased its frequency in such
  populations
• Lactose tolerance evolved in environments where
  milk is a major source of nutrition
• A similar mutation also occurred in the Fulani
  people of Western Africa a couple thousand years
  ago

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LACTOSE INTOLERANCE

• Dairy farming was the cultural practice that
  drove the evolution of lactose tolerance
• Highest levels of lactase deficiency in Asian
  populations not involved in dairy farming
• Low levels of lactase deficiency in European
  populations with long histories of dairy farming
• Low levels of lactase deficiency in West African
  populations relying extensively on milk in their
  diets

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LACTOSE INTOLERANCE

• Western Europeans colonized other areas of the
  world over the past five centuries
• Gene conferring lactase traveled with them
• Frequency of lactose tolerance increased in
  contacted populations

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ROLES OF CARBOHYDRATES

• Longer-term energy storage
• Starch and glycogen are storage polysaccharides
• Plants store excess sugars as starch
• Animals store excess sugars as glycogen
• Monosaccharides can be released via hydrolysis

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ROLES OF CARBOHYDRATES

• Structural roles
• Cellulose is a major component of plant cell
  walls
• Most abundant organic compound on earth
• Polymer of glucose

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ROLES OF CARBOHYDRATES

• Structural roles
• The covalent linkages between monomers differ
  between starch and cellulose
• Different three-dimensional shapes
• Linkages between starch monomers are easily
  hydrolyzed
• Very few organisms can hydrolyze linkages
  between cellulose monomers
• Lack the required enzymes

70
ROLES OF CARBOHYDRATES

• Structural roles
• Some microbes can digest cellulose
• e.g., Cellulose-digesting bacteria in a cows
  rumen
• e.g., Cellulose-digesting microbes in a termites
  gut
• These relationships are examples of mutualism
• Both organisms benefit from the interaction
• How?

71
ROLES OF CARBOHYDRATES

• Structural roles
• Chitin is a major component of fungal cell walls
  and arthropod exoskeletons
• Hardened with calcium carbonate in arthropods
• Structure similar to cellulose

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ROLES OF CARBOHYDRATES
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ROLES OF CARBOHYDRATES

• Cell communication
• Glycoproteins and glycolipids on cell surface

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LIPIDS

• Not polymers
• Comprised almost exclusively of C and H
• Nonpolar bonds ? no H-bonding
• Generally interact poorly with water
• Hydrophobic

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LIPIDS

• Key roles of lipids
• Energy storage
• Insulation
• Membrane components
• Cell communication

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LIPIDS

• Major classes of lipids
• Fats and oils
• Phospholipids
• Steroids

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LIPIDS

• Fats and oils
• Triacylglycerols or triglycerides
• Not polymers
• Assembled from smaller molecules through
  condensation reactions
• Glycerol
• Three fatty acids

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LIPIDS

• Fats and oils
• Fatty acids contain long carbon skeletons
• Generally 16 18 carbons
• These carbon skeletons may contain only single
  bonds
• Saturated
• These skeletons may contain double bonds
• Unsaturated
• Polyunsaturated
• Cause chain to bend

79
LIPIDS

• Fats and oils
• Saturated fats
• Present in fatty meats, dairy products, coconut
  oil, etc.
• Possess only single bonds in fatty acid tails
• Molecules can pack together tightly
• Solid at room temperature

80
LIPIDS

• Fats and oils
• Unsaturated fats (oils)
• Present in most plant and fish oils, etc.
• Possess double bonds in fatty acid tails
• Molecules cannot pack together as tightly
• Generally liquid at room temperature

81
LIPIDS

• Phospholipids
• Similar to fats
• Glycerol
• 2 fatty acids
• Phosphate
• (Inositol, choline, etc.)
• Amphipathic
• Hydrophilic region
• Hydrophobic region

82
LIPIDS

• Phospholipids
• Aggregate in water-rich environments
• Micelles
• Phospholipid bilayers
• Key components of cell membranes
• Hydrophobic regions are hidden from water
• Hydrophilic regions are in contact with water

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LIPIDS

• Cholesterol
• Steroid
• Amphipathic
• Membrane antifreeze
• Prevents membrane solidification at low
  temperatures
• Precursor for all steroid hormones

84
LIPIDS

• Steroid hormones
• Synthesized from cholesterol
• Involved in a variety of body functions
• e.g., Development
• e.g., Reproduction
• e.g., Salt regulation
• e.g., Sugar biosynthesis
• e.g., Water regulation
• etc.

85
LIPIDS
86
PROTEINS

• Comprise over 50 of dry mass of most cells
• Very diverse in structure and function
• Consist of one or more polypeptides
• Polypeptides are chains of amino acids

87
PROTEINS

• Proteins are polymers of amino acids
• 20 different amino acids
• Different R groups
• Some hydrophilic
• Some hydrophobic

88
PROTEINS

• Amino acids are linked via condensation reactions
• Amino acid of one reacts with the acid group of
  another
• Form covalent peptide bonds
• All proteins are made by assembling the same 20
  amino acids in different orders to different
  lengths

89
PROTEINS

• Humans can make tens of thousands of distinctly
  different proteins
• All use the same 20 amino acids
• Different orders
• Different lengths
• How many distinctly different tripeptides can be
  assembled from these 20 amino acids?
• tetrapeptides?

90
ESSENTIAL NONESSENTIAL

• All organisms require all 20 amino acids
• Humans can manufacture only ten of these amino
  acids from precursor molecules
• Non-essential amino acids
• Humans cannot manufacture the other ten amino
  acids
• Essential amino acids
• Must be acquired from diet
• The bacterium Escherichia coli can manufacture
  all twenty amino acids
• All amino acids are nonessential for E. coli
• Humans can produce 12 amino acids from
  precursor molecules, but the precursor molecules
  for the production of two of these 12 amino acids
  are themselves essential amino acids (met ? cys,
  phe ? tyr)

91
ROLES OF PROTEINS

• Key roles of proteins
• Structural
• Movement
• Transport
• Chemical messengers
• Receptors
• Storage
• Defensive
• Enzymes

92
ROLES OF PROTEINS

• Hormones are one group of proteins
• Chemical messengers involved in numerous
  processes
• e.g., Insulin, glucagon, growth hormone, etc.
• Remember, not all hormones are proteins
• Steroid hormones are lipids
• Other hormones are proteins

93
ROLES OF PROTEINS

• Enzymes are biological catalysts
• One important class of proteins
• Speed up the rate of chemical reactions
• Perhaps 10,000 times faster
• Not consumed in this reactions
• Highly specific

94
PROTEIN CONFORMATION

• Each protein folds up into a particular
  three-dimensional shape
• Protein function is related to its structure

95
PROTEIN CONFORMATION

• Each protein folds up into a particular
  three-dimensional shape
• Four levels of protein organization are
  recognized
• Primary (1o) structure
• Secondary (2o) structure
• Tertiary (3o) structure
• Quaternary (4o) structure

96
PROTEIN CONFORMATION

• Primary structure
• Linear sequence of amino acids
• Genetically determined
• Ultimately determines higher structural levels
• The primary structure of the enzyme lysozyme is
  depicted
• 129 amino acids long

97
PROTEIN CONFORMATION

• Some regions of the polypeptide exhibit secondary
  structure
• Formed by H-bonding at regular intervals along
  the polypeptide backbone
• Two common types of secondary structure
• Alpha-helices
• Beta-pleated sheets

98
PROTEIN CONFORMATION

• Tertiary structure involve interactions among
  R-groups
• Four main factors
• Hydrogen bonds
• Ionic attractions
• Hydrophobic interactions
• Covalent bonds
• Disulfide bridges

99
PROTEIN CONFORMATION

• Quaternary structure results from interactions
  between multiple polypeptide chains
• Not all proteins possess multiple polypeptide
  chains
• Not all proteins possess quaternary structure

100
PROTEIN CONFORMATION
101
PROTEIN CONFORMATION

• The three-dimensional conformation of a protein
  is critical to its function
• Form determines function
• Altered conformation can compromise function
• Altered structure at any level can alter the
  final conformation
• Altered chemical bonds can alter conformation

102
MUTATION CONFORMATION

• The primary structure of a polypeptide is
  genetically determined
• Primary structure ultimately determines the final
  shape of a protein
• Mutations can alter the DNA sequence of a gene
• Can alter the primary structure of the
  polypeptide
• Can result in an altered three-dimensional shape
• Basis of many genetic disorders

103
PROTEIN DENATURATION

• Proteins can be denatured by a variety of factors
• Temperature
• pH
• etc.
• Denaturation alters the conformation of the
  protein
• Often irreversible
• It is difficult to un-hard-boil an egg

104
NUCLEIC ACIDS

• Two classes of nucleic acids are found in cells
• Deoxyribonucleic acid
• DNA
• Ribonucleic acid
• RNA
• Many of the functions of these nucleic acids are
  related or overlapping

105
NUCLEIC ACIDS

• DNA
• Polymer of deoxynucleotides
• Genetic material of all cellular life and of some
  viruses
• Organized into genes
• Blueprints for proteins

• RNA
• Polymer of nucleotides
• Genetic material of some viruses
• Intermediates in gene expression
• Ribosome components
• Some possess enzyme-like activity
• Ribozymes

106
(DEOXY)RIBONUCLEOTIDES

• Nucleic acids are polymers
• DNA monomers are deoxyribonucleotides
• RNA monomers are ribonucleotides

107
(DEOXY)RIBONUCLEOTIDES

• Nucleic acid monomers consist of three parts
• Sugar
• Nitrogenous base
• Phosphate group(s)
• These three parts are assembled by condensation
  reactions

108
(DEOXY)RIBONUCLEOTIDES

• Both DNA and RNA possess a pentose sugar
• Ribose in RNA
• Deoxyribose in DNA
• Lacks the 2 OH group possessed by ribose

?
109
(DEOXY)RIBONUCLEOTIDES

• Both DNA and RNA possess four nitrogenous bases
• Guanine
• Adenine
• Cytosine
• Thymine (in DNA)
• Uracil (in RNA)

110
(DEOXY)RIBONUCLEOTIDES

• One or more phosphate groups are attached to the
  5 carbon of (deoxy)ribose
• Triphosphates used in polynucleotide synthesis
• Only one is incorporated into a DNA or RNA
  chain

111
(DEOXY)RIBONUCLEOTIDES

• Some ribonucleotides have additional functions
• e.g., ATP is involved in energy transfers
  within cells

112
POLYNUCLEOTIDES

• Nucleotides are joined via condensation reactions
• 3 OH and 5 phosphate OH
• New nucleotides are added to the 3 end of
  growing chain
• Two strands of double-stranded polynucleotides
  are NOT covalently linked
• Interact through H-bonds

113
POLYNUCLEOTIDES

• Structure of a single strand of DNA or RNA
• Backbone of alternating sugar and phosphate
  groups
• Nitrogenous bases projecting from this backbone

114
POLYNUCLEOTIDES

• Most DNA and some RNA is double-stranded
• Bases project from the sugar-phosphate backbone
• Bases of two strands interact through H-bonds

115
POLYNUCLEOTIDES

• DNA is organized into units called genes
• A gene is a blueprint for a protein
• RNA is an intermediate in gene expression
• DNA ? RNA ? protein

116
ORIGIN OF LIFE

• Life on Earth initially arose amidst a sea of
  various biological molecules
• e.g., Amino acids, sugars, purines, ATP, etc.
• The production and accumulation of these
  biological molecules preceded the origin of life
  on Earth

117
ORIGIN OF LIFE

• Stanley Miller and Harold Urey recreated the
  assumed early atmosphere (1953)
• Contained H2O, H2, CH4, and NH3
• Lacked free O2
• Energy input in forms of heat and electrical
  sparks
• Mimic geothermal heat and lightning

118
ORIGIN OF LIFE

• The initial Miller-Urey experiment and various
  similar experiments succeeded in producing
• All 20 amino acids
• Several sugars
• Lipids
• Purines and pyrimidines
• ATP (when phosphate was added)
• etc.

119
ORIGIN OF LIFE

• The atmosphere replicated in these experiments
  likely differed from the earths early atmosphere
• Atmosphere likely possessed little or no O2
• Atmosphere likely possessed more CO, CO2, and N2
  than that in Millers experiment
• Still, the Miller-Urey experiment did demonstrate
  that key organic molecules critical to life could
  be produced abiotically from inorganic precursors

120
ORIGIN OF LIFE

• Other researchers have used combinations of gases
  based on our current understanding of Earths
  early atmosphere
• Similar results were achieved
• Organic molecules can be abiotically produced in
  an atmosphere composed primarily of H2O, CO, CO2,
  and N2

121
APPENDIX

• CLASSES OF PROTEINS

122
ROLES OF PROTEINS

• Structural proteins
• e.g., Collagen, elastin, keratin, etc.

123
ROLES OF PROTEINS

• Proteins facilitating movement
• e.g., Actin, myosin, tubulin, etc.

124
ROLES OF PROTEINS

• Transport proteins
• e.g., Hemoglobin, lac permease, etc.

125
ROLES OF PROTEINS

• Chemical messengers
• e.g., Hormones and neurotransmitters
• Receptors
• Respond to chemical messengers

126
ROLES OF PROTEINS

• Storage
• e.g., Casein, ovalbumin, etc.

127
ROLES OF PROTEINS

• Defensive
• e.g., Antibodies, fibrin, etc.

128
ROLES OF PROTEINS

• Enzymes
• Highly specific catalysts of chemical reactions

129
REFERENCES

• Campbell, Neil A. and Reese, Jane B. Biology,
  7th edition. Pearson Education, Inc. 2005.
• Campbell, Neil A., Reese, Jane B., Taylor, Martha
  R., and Simon, Eric J. Biology, Concepts and
  Connections, 5th edition. Pearson Education,
  Inc. 2006.
• Nester, Eugene W., Anderson, Denise G., Roberts,
  C. Evans Jr., and Nester, Martha T.
  Microbiology, A Human Perspective, 5th edition.
  McGraw-Hill Companies, Inc. 2007.
• Limson, Janice. 2002. http//www.scienceinafrica
  .co.za/2002/june/lactose.htm