Theme: Follow the carbon

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Theme Follow the carbon

• Lecture 2
• Building Blocks of Life

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Basic Necessities for Living Organisms

• Building blocks organic molecules (based on C)
  and nutrients N, P, Fe, S.
• Energy (food)
• Solvent liquid water (H2O)

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Carbon is abundant in the Universe but Earth is
depleted in carbon. So why did life choose
carbon?
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Why Carbon?

• Carbon atom can form up to 4 chemical bonds with
  many other atoms can form long and complex
  molecules
• Carbon can form compounds that readily dissolve
  in water.

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Chemical element is an atom distinguished by the
number of protons in the nucleus
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Periodic table of the chemical elements

• The layout of the periodic table
• demonstrates recurring ("periodic")
• chemical properties.
• Elements are listed in order of
• increasing atomic number (i.e. the
• number of protons in the atomic
• nucleus).
• Rows are arranged so that elements
• with similar properties fall into the same
• vertical columns ("groups").
• According to quantum mechanical
• theories of electron configuration within
• atoms, each horizontal row ("period") in
• the table corresponded to the filling of a
• quantum shell of electrons.

Dmitriy Mendeleev
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A simplified version of the periodic table
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Electrons can reside only on specific orbits
(shells) Electrons on the inner shells have
lower energy There is a max (optimal) number of
electrons per each shell 1 shell 2 electrons
(S electrons) 2 shell 8 electrons 2(S
electrons) 6 (P electrons)
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Hydrogen
Outer shell/orbits
Typically only electrons from the outer shell
(valent electrons) engage in chemical bonds
Carbon
Elements want to have optimal number of
electrons on the outer shell
Helium
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Chemical bonds

• Covalent (strong)
• Ionic (strong)
• Metallic (strong)
• Hydrogen (weak)

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Covalent bond

• Electrons are shared between atoms
• Polar and non-polar

diamond
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Ionic bond

• Electrons are not shared between atoms

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Hydrogen bond

• Occurs between electronegative
• (electron taker) atom and
• hydrogen atom bonded to N, O or F

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Carbon has 4 valent electrons can form up to 4
bonds
Methane
Ethane
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Draw all possible C-H moleculeswith 5 Carbon
atoms.

• Assume that each Carbon atom forms 4 chemical
  bonds
• Remember that each Carbon atom can form chemical
  bond with either hydrogen or another Carbon atom.
  

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ethene
benzene
ethanol
fullerene
diamond
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Polymerization

• A polymer is a substance composed of molecules
  with large molecular mass composed of repeating
  structural units, or monomers, connected by
  covalent chemical bonds. Well known examples of
  polymers include plastics and DNA.

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Silicon life?

• Si is abundant and also can form four bonds at
  once (like C). But!
• Si bonds are much weaker complex molecules
  based on Si will be fragile
• Si does not form double bonds less variety

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Organic and Inorganic Carbon C can be in
reduced or oxidized forms. Organic
carbon Inorganic carbon (reduced)
(oxidized) CH2O CO2 carbon
dioxide H2CO3 carbonic acid Example HCO3?
bicarbonate ion Glucose -- C6H12O6 CO3
carbonate ion
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Inorganic carbon (C-O bonds only)
Organic carbon (has C-H and C-C bonds)
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Coal
Oil
JENNY HAGER/ THE IMAGE WORKS
http//www.nationalfuelgas.com
Organic carbon
http//www.upl.cs.wisc.edu/stroker/jungle.jpg
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Inorganic carbon
Seashells
http//www.cmas-md.org/Images/Sanjay/UnivTop4.jpg
Coral
http//www.summerclouds.com/Vero/Sea20Shells.jpg
http//educate.si.edu/lessons/currkits/ocean/
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Four types of organic macromoleculesin living
systems.

• Most of the molecules in the living systems are
  water (H2O) and large organic macromolecules
• Lipids
• Carbohydrates
• Proteins
• Nucleic Acids

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Lipids (fats and oils)

• Representatives fatty acids and cholesterol
• Poorly soluble
• Good (concentrated)
• energy source
• Flexible
• (cell membrane material)

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(No Transcript)
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Carbohydrates (sugars, starches, carbs)

• Representatives
• Glucose, Fructose
• Many hydroxyl
• groups (-OH)
• Soluble in water
• Form Polysaccharides
• Good energy source
• Structural support for
• organisms (cellulose
• - the main constituent of wood)

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Glucose
Fructose
Table sugar
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Glucose polymerization
H2O
Linked by dehydration reaction
Polysaccharides
In starch molecule (potato) there can be 100s
thousands of glucose units
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Proteins

• Proteios primary
• Long trains of amino acids
• Different proteins have different sequence of
  amino acids
• 20 amino acids used in any organism
• Some provide structure (fingernails, hair)
• Some serve as catalysts
• Enzymes proteins with catalitic properties

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L-Alanine
Glycine
Linked by dehydration reaction
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Catalysts in Chemistry

• Suppose chemical reaction
• A B ? AB is a slow reaction
• The same reaction can be accelerated with
  catalyst (D)
• A D ? AD fast step
• B AD ? AB D fast step
• The net result is still
• A B ? AB but it is much faster

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Proteins (continued)

• Even though there are 70 amino acids any known
  life uses only 20
• Amino acids derived abiotically are a mix of both
  left-handed and right-handed ones. Biological
  amino acids are only left-handed.
• Chirality
• Was there a common ancestor for all life?

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Biology uses only left-handed Alanine
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Summary

• All life on Earth is carbon (C) and water (H2O)
  based
• C atom can form up to 4 covalent bonds with many
  other atoms can form complicated molecules
• C can be in either organic or inorganic form
• All living systems are made of large organic
  molecules (macromolecules) lipids,
  carbohydrates, protein, nucleic acids