Chemical Evolution

1
Chemical Evolution

• Carbohydrates and Lipids

2
Biochemistry

• Systematic study of the molecular nature of life
  processes the chemicals that make up of living
  systems (biochemicals), their organization into
  cells, and their chemical interactions
• Biochemicals have no life in themselves
• Chemical interactions which sustain life occur
  only when biochemicals become organized into
  cells in tissues

3
Biochemicals

• The major biochemicals are carbohydrates, lipids
  and proteins which provide energy and materials
  and nucleic acids, which provide hereditary
  information needed to sustain life
• According to Oparin, each was first produced
  abiotically by chemical evol-ution and then
  assembled as first cell

4
Structure/Property Generalizations

• Chemical, physical, and biological properties of
  biochemicals are determined by their structures
• Structurally, biochemicals involve large
  molecules frequently composed of repeating
  components (polymers)

5
Carbohydrates

• Carbohydrates - substances having alcohol (-OH)
  and either aldehyde (HCO) or ketone (CO)
  functional groups
• Function provide energy and materials
• Structures Chain and ring forms coexist with
  the ring form usually predominating in aqueous
  solutions

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Carbohydrates - polyhydroxy aldehydes or ketones
Hill/Kolb, "Chemistry for Changing Times",
7th,Prentice Hall, NJ, 19995,456
7
Ring Structure for Glucose
Brady/Holum, "Fundamentals of Chemistry", Wiley,
NY, 1988, 1029
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(4 C)
Abiotic Synthesis of Carbohydrates (sugars)
(3 C)
(5 C)
(6 C)
Mason, Chemical Evolution,Oxford, UK, 1991, 241
10
Monosaccharides - One Ring
Joesten, World of Chemistry Essentials, Saunders
FL, 1993, 206
11
Disaccharides
Joesten, World of Chemistry Essentials, Saunders
FL, 1993, 206
12
Polysaccharide - Many Rings
Glucose is stored in the human body as glycogen
which is a polysaccharide having a structure
similar to that for starch
Hill/Kolb, "Chemistry for Changing Times",
7th,Prentice Hall, NJ, 19995,457
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Energy-providing Function of Carbohydrates

• Glucose is produced in plants by solar energy and
  chlorophyll catalyst 6 CO2 6H2O gt C6H12O6
  6 O2 DH gt 0
• Glucose is water soluble (H-bonding) and is
  transported to cells where it serves as the
  source of energy by means of the reaction
• C6H12O6 6O2 gt 6CO2 6H2ODH lt 0

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Flow of Energy and Matter Between Plants and
Animals
Joesten/Wood, World of Chemistry, 2nd, Saunders,
NY, 1996, 491
16
Lipids

• Lipids are the components of cells that are
  insoluble in water but soluble in non-polar
  solvents
• Include fats, oils, waxes, fatty acids, steroids,
  and some vitamins

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Fatty Acids

• Fatty acids are organic acids RCOOH having 7-21
  carbon atoms in R group
• Fatty acids are classified according to the
  number of double bonds in the R-group (saturated,
  if no double bonds mono-unsaturated, if one
  double bond and poly-unsaturated if more than
  one double bond)

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(All C to C single bonds)
(One C to C double bond)
(More than one C to C double bond)
Tro,394
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Geometric Isomers

• Geometric isomers have the same atoms and the
  same bonds, but different spatial orientations
  around a double bond
• Differentiated by drawing an imaginary plane
  perpendicular to the plane containing the CC
  (shown as red dotted lines on next slide)

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Examples of Geometric Isomers
Two like groups located on adjacent C atoms- both
above or both below the ? red plane cis-isomer
Two like groups located on adjacent C atoms- one
above and one below the ? red plane trans-isomer
http//www.wpbschoolhouse.btinternet.co.uk/page06/
AlkeneStructure.htm
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Horton, Biochemistry, 3rd, Prentice Hall,NJ,2002,
167
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Fats and Oils

• Fats are tri-esters of saturated fatty acids and
  glycerol - solids at room temperature
• Oils are tri-esters of unsaturated fatty acids -
  liquids at room temperature - kinks at cis double
  bonds decrease effectiveness of London Forces
  between chains

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Abiotic Synthesis of Fats and Oils from Fatty
Acids
Joesten, World of Chemistry Essentials, Saunders
FL, 1993, 210
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Cis and Trans Fatty Acids
Double bonds bind carbon atoms tightly and
prevent rotation of the carbon atoms along the
bond axis. This gives rise to configurational
isomers which are arrangements of atoms that can
only be changed by breaking the bonds.
Cis-9-octadecenoic acid (Oleic acid)
Trans-9-octadecenoic acid (Elaidic acid)
Liquid oil - bent structure limits LDF between
adjacent chain in triple ester
Solid fat - structure promotes stronger LDF
between adjacent chains in triple ester
http//www.myfoodforhealth.com/fats.htmFatty20Ac
id20Configurations
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Metabolism of Fats
Cis-acids assumed. Trans-acids problematic.
http//www.omega3sealoil.com
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Membrane Function of Lipids

• One function of lipids is to serve as a membrane
  which separates compon-ents of an animal cell
• A fat or oil is converted to a glycero-phospholipi
  d by replacing one non-polar fatty acid unit with
  a polar unit - combination of a phosphate unit
  and an amino alcohol unit

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Lipids of Cell Membranes
Brady/Holum, Chemistry, 3rd, Wiley,NY, 2000, 1060.
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Glycerophospholipid Representation
Brady/Holum, Chemistry, 3rd, Wiley,NY, 2000, 1060.
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The Lipid Bilayer of Animal Cell Membranes
Structural integrity of an animal cell depends
entirely on the sum of many weak forces London
dispersion, dipole, and hydrogen bonding
Brady/Holum, Chemistry, 3rd, Wiley,NY, 2000, 1061.
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Lipids overview

• Lipids are characterized by their poor
  interaction with water - hydrophobic
• physical properties of lipids
• Types of lipids
• Function in cells

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Lipids are non-polar

• Hydrocarbons
• electrons are shared equally
• no partial charges
• cannot H-bond with water
• disruption of H-bonding in water
• water molecules must organize themselves around
  hydrophobic molecules
• hydrophobic molecules pushed together to minimize
  disruption

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Triglycerides Fats/Oils

• Triglycerides glycerol 3 fatty acids
• Function as energy storage and insulation

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Saturated vs. Unsaturated Fats

• Saturated
• maximum number of hydrogens
• no double bonds
• more energy storage (more calories)
• less fluid because straight
• butter, lard, fat

• Unsaturated
• less than maximum number of hydrogens
• double bonds present
• less energy storage
• more fluid because bent
• vegetable oils

34
Phospholipid structure

• Phospholipids - glycerol 2 fatty acids
  phosphate polar group.
• amphipathic
• hydrophobic tail hydrophilic head

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Lipid Bilayers

• When mixed with water, phospholipids
  spontaneously form a lipid bilayer.
• Hydrophilic portion of phospholipid on surface,
  exposed to water.
• Hydrophobic portion in central region, away from
  water.
• Lipid bilayers formthe basis of membrane
  structure

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Other Lipids

• Isoprenoids - carotene, vitamin A, E, K
• Sterols
• cholesterol, a component of membranes
• steroid hormones, testosterone, estrogen,
  cortisone

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Other Lipids

• Isoprenoids - carotene, vitamin A, E, K
• Sterols
• cholesterol, a component of membranes
• steroid hormones, testosterone, estrogen,
  cortisone

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Lipids

• Not true polymers. These compounds are composed
  largely of carbon and hydrogen.
• Most include fatty acids
• Fats
• Phospholipids
• Waxes
• Steroids and derivatives no FAs
• Tend to be insoluble in water

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Fatty Acids

• Carboxyl group (-COOH) at one end this is what
  makes them acid
• Carbon backbone (up to 36 C atoms)
• Saturated - Single bonds between carbons
• Unsaturated - One or more double bonds

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Fats

• Fats are lipids whose main function is energy
  storage
• They are also called triglycerides or
  triacylglycerol
• Three fatty acids linked to one glycerol molecule
• Triglycerides - stored as droplets in adipose
  tissue

43

• Gram for gram, fats yield twice the energy when
• degraded, compared to complex carbohydrates
• Many repeated CH2 in the fatty acid part

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• Unsaturated fats (plant oils)- the fatty acids
  contain double bonds

• These prevent the fats from solidifying at room
  temperature

• Saturated fats (lard) lack double bonds

• They are solid at room temperature

Figure 3.8C
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We need fat!

• The major energy source for our bodies
• Helps vitamins A,D,E, and K get transported
  through the bloodstream
• Structural materials in cell membranes
• Insulation, padding for organs

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Functions of fats
Energy storage
Insulation
Protection
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Hydrogenated oils

• Also called Trans fat
• solidify plant oils by adding hydrogens
• lowers HDLs and increases LDLs
• heart disease 1 killer
• before 1920, heart disease unheard of
• FDA refuses to set max recommended daily
  allowance, because safe level is zero

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Phospholipids

• Phospholipids are a major component of cell
  membranes
• glycerol backbone, two fatty acid tails and a
  hydrophylic phosphate head

Phospholipid bilayer or cell membrane
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Waxes

• Long-chain fatty acid linked an alcohol
• Firm consistency, repel water
• Important in water-proofing

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Steroids

• Always have same ring pattern
• Cholesterol common in animal cell membranes
• Steroids are often hormones sex hormones

Figure 3.9
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Anabolic steroids and health risks

• Anabolic steroids are usually synthetic variants
  of testosterone
• Use of these substances can cause serious health
  problems

Figure 3.10
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• DNA /RNA action

• Stretches of a DNA molecule called genes
  program the amino acid sequences of
  proteins
• DNA information is transcribed into RNA
• RNA is then translated into the primary
  structure of proteins

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Make-up Slides

• The following slides were omitted from earlier
  handouts
• Next slide was omitted from 2/15/05 handout
• The last two slides were omitted from the 2/17/05
  handout

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Theory of Continental Drift - Wegener 1915
Pangaea "all the land" - one continent that split
to form all the present day continents
http//www.agen.ufl.edu/chyn/age2062/lect/lect_28
/lect_28.htm
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Table of Bond Energies
DH Endo - Exo DH Sum of BE of all bonds in
reactants - Sum of BE
of all bonds in products




http//telstar.ote.cmu.edu/environ/m3/s3/07stabili
ty.shtml
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Apparatus for testing Oparin's Hypothesis -
produces bioorganic compounds from a simulated
prim-itive atmosphere using spark discharges to
simulate lightning (S. Miller- 1955)
Miller, Livingin Environment, 12th, Thompson, CA,
2002, 104