Finish Follow the carbon Start Follow the energy

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Finish Follow the carbon Start Follow the
energy

• Lecture 5

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Putting things together

• Small organic carbon molecules could have come
  from three sources in the prebiotic world
• Synthesis in the atmosphere
• Synthesis in the hydrothermal vents
• Synthesis in space and delivery via meteorites

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Polymerization

• Polymerization produces longer molecules from
  simple organic molecules
• One type of polymerization is through the loss of
  water

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Minerals can help polymerization

• Organic soup was probably too dilute to form very
  long molecules
• Minerals (like clay) can provide a repeating
  pattern to act as a template for polymerization
• Small organic molecules could have stuck to the
  mineral surface

Kaolinite
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Concept of the RNA world
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Concept of the RNA world

• Short strands of RNA-like molecules were produced
  spontaneously (with the help of minerals)
• Eventually some of the RNA-like molecules were
  able to catalyze their own replication
• Copying errors introduced mutations and therefore
  Darwinian-like evolution

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Formation of the cell membrane

• Some lipids have hydrophilic (love water) head
  and hydrophobic tail
• In solution these lipids can form monolayers,
  bilayers and bilayer vesicles spontaneously
  pre-cells.

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Monolayer
Micells
Bilayer
Bilayer vesicle
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First DNA-based Life

• Through the natural selection life figured out
  that
• DNA is a better way to store the hereditary
  information (better protected, less mistakes
  during replication)
• Proteins are more efficient catalysts than RNA

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EARTH TODAY
Organics from space
Abiotic synthetic reactions on the early Earth
Prebiotic soup
Prebiotic polymers
Protein/DNA world Last Common Ancestor
RNA world
The origin of life
Bada Lazcano (Science, 2002)
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Follow the Energy

• Energy ability to do work
• Work (mechanical work) W F(force) x
  d(displacement)
• Different kinds of Energy
• Kinetic Ek ½ mv2
• Potential Ep (gravitational) mgh (h
  height g gravitational acceleration)
• Thermal random motion of particles (molecules
  and atoms)
• Chemical energy rearranging electrons
• Nuclear energy nuclear fusion, nuclear fission
  rearranging nuclones
• Electromagnetic energy electomagnetic waves
  (light)

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Conservation of Energy

• In any isolated (closed) system energy is
  conserved
• Ep Ek Etherm Echem Ep? Ek? Etherm?
  Echem? constant

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Energy/Work units

• Units One Joule is the work done, or energy
  expended, by a force of one Newton (N) moving an
  object one meter along the direction of the force
• 1 Joule 1 N 1 meter 1 kg 1 m/sec2 1
  meter
• The force of Earths gravity on the 220 pounds
  human is about 1000 N
• 1 Calorie (food energy, upper case C) 4184 J

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Example

• Suppose an athlete lifted a barbell with weights
  (220 pounds) from the ground to 6 feet. How many
  Calories did he use?
• Recall that Ep mgh where g 9.8 m/s2
• 1 foot 0.3 meters
• 1 pound 0.45 kg

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• Not all kinds of energy are useful
• No examples of life using gravitational, low
  frequency electromagnetic (radio), nuclear
  energy.

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Entropy

• Entropy a measure of disorder in the physical
  system
• the second law of thermodynamics the universe,
  or in any isolated system, the degree of disorder
  (entropy) can only increase
• the most probable state is the most disordered
• the movement towards disordered state is a
  spontaneous process

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Which of the players has a hand with the higher
Entropy?
40 combinations
million combinations
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But! Life produces order!
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• Is the second law of thermodynamics violated in
  the living cells? No.
• Cell is not an isolated system it takes in
  energy from its environment to generate order
  within itself
• Part of the energy that the cell uses is
  converted into heat.
• The heat is discharged into the cell's
  environment and disorders it.
• The total entropy increases

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ATP

• Every living cell uses ATP (adenosine
  triphosphate) to store and release energy

Energy out
Energy in
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How does life get the energy?

• Photosynthesis
• Oxygenic
• CO2 H2O h? (Energy) ? CH2O O2
• B) Anoxygenic
• CO2 2H2S h? (Energy) ? CH2O 2S H2O
• In reality
• 6CO2 6H2O h? (Energy) ? C6H12O6 6O2

Glucose
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How does life extract the energy?

• Respiration
• CH2O O2 ? CO2 H2O Energy
• In reality
• C6H12O6 6O2 ? 6CO2 6H2O Energy
• Fermentation
• C6H12O6 ? 2CO2 2C2H6O Energy

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But there are ways to get energy without
photosynthesis.

• Methanogenesis
• CO2 4 H2 ? CH4 2H2O Energy
• Sulfate reduction
• 4H2 SO42- ? S2- 4H2O Energy

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Two primary sources of energy
Sun
Earths Interior
What about fossil fuels?
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Classification of living organisms by carbon and
energy sources

• Autotroph organism gets carbon directly from
  the atmosphere (CO2)
• Heterotroph organism gets carbon by consuming
  preexisting organics
• Photo energy to make ATP comes from light
• Chemo energy to make ATP comes from chemical
  reactions (chemical disequilibrium)
• Humans are .. Plants are .