Carbon%20and%20Molecular%20Diversity

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Carbon and Molecular Diversity

• Based on Chapter 4

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Major Elements of life
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Compounds and Molecules
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Structure and Function

• Carbon molecule and ring structure
• Polysaccharides

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Importance of Carbon

• Most molecules from which living organisms are
  derived are based on C.
• C has the ability to form large, complex and
  diverse molecules.
• Cells and tissues are made up of these basic
  molecules carbohydrates, lipids, proteins and
  nucleic acids.
• The study that deals with C and and C-H molecules
  (hydrocarbons) is called organic chemistry.
• In order to get familiar with macromolecules, we
  need to examine C, hydrocarbons and the
  functional groups which bond to hydrocarbons.

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Properties of Carbon

• Chemical characteristics and bonds formed by an
  atom are determined by the atoms electrons.
• Carbon has 6 electrons (2 first shell, 4 second
  shell)
• With 4 valence electrons, it has little tendency
  to gain or loose electrons and form ionic bonds.
• It forms covalent bonds to become stable. Most
  commonly with H, O and N
• These bonds are in 4 different directions and C
  is known as having tetravalence because of this.
• Carbon will form double and triple bonds with
  other C atoms. Even though you will see molecules
  written in their structural formula as flat, they
  are 3d structures and their molecular shape
  often determine their function.

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Hydrocarbons

• When C is not bonding to itself, it covalently
  bonds to other atoms (H, O and N)
• The basic C compound is called a hydrocarbon,
  formed from C and H.

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Hydrocarbons

• Hydrocarbons vary in
• The number of C on the chain
• Straight, branching, or ring structures
• Where and how many H atoms are attached to the
  carbon chain.
• Most hydrocarbons have similar properties (the
  C-H bond is energy rich) so hydrocarbons are
  capable of storing vast amounts of energy (fats
  and petroleum)
• Carbon variations that differ only in the
  arrangements of atoms are called isomers.

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Isomers

• Compounds that have the same molecular formula,
  but different structures and thus different
  functions.
• There are 3 types of isomers
• Structural
• Geometric
• Enantiomers

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Structural Isomers

• Vary in their covalent bonding arrangement.
• Also may vary in the placement of double C bonds.

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Geometric Isomers

• Have the same covalent partnerships but differ in
  their spatial arrangements.
• Geometric isomers share common covalent bonding,
  but because double bonds are inflexible (prevent
  rotation) compared to single bonds which rotate
  freely around the bonds axis.
• The differing shape of geometric isomers can
  dramatically affect their biological function
  (sometimes called the cis-trans difference).

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Enantiomers (stereoisomers)

• Molecules that are mirror images of each other
  and have the same molecular formula.
• Enantiomers are formed when 4 different molecular
  groups are bonded to a central (asymmetric)
  carbon so that they can be arranged in 2
  different ways.
• The different shapes of enantiomers can
  dramatically alter function.
• One example is Vitamin E which has a L and D
  form. One is more active and found naturally, the
  other is frequent in vitamin pills but lacks the
  same biologic activity.
• L-dopa example

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Functional Groups

• These are molecular fragments which, when
  substituted for one or more H atoms in a
  hydrocarbon, confer particular chemical
  properties to the new compound.1
• The functional group determines the behavior of
  the molecule and is consistent in different
  organic molecules.
• There are 6 main functional groups we will
  consider.

1Richardson, Rosemary, 2003 http//www.scidiv.bcc.
ctc.edu/rkr/
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Hydroxyl Group

• The hydroxyl function group is formed by an
  oxygen bonded to a hydrogen, with the second bond
  of the oxygen free to attach to the carbon chain
  (-OH).
• Hydroxyl functional groups confer properties of
  an alcohol to hydrocarbons.
• Hydroxyl functional groups are polar (the oxygen
  end's electronegativity), and attract water. This
  helps dissolve in water those macromolecules,
  such as sugars, which have hydroxyl functional
  groups in their structure.
• The naming convention for alcohols is to have the
  alcohol end in "ol" and the prefix be determined
  by the number of carbons (based on the alkane or
  pure hydrocarbon naming convention). For example,
  the two-carbon alcohol is ethanol.1

1Richardson, Rosemary, 2003 http//www.scidiv.bcc.
ctc.edu/rkr/
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Carbonyl Group

• The carbonyl functional group is a double bonded
  oxygen (O).
• Carbonyl functional groups confer properties of
  aldehydes or ketones to hydrocarbons.
• Because double bonds restrict flexibility and
  rotation on the carbon skeleton, the location of
  the carbonyl functional group affects structure,
  and function.
• Carbonyl functional groups attached to an "end"
  carbon form aldehydes. Carbonyl functional groups
  attached to a non-end carbon form ketones. The
  naming convention for ketones uses the suffix
  -one" and aldehydes the suffix -al". The prefix
  may be determined by the number of carbons. It is
  not always so. For example, propanal is the
  3-carbon aldehyde, but the 3-carbon ketone, by
  convention, is called acetone.

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Carboxyl Group

• The carboxyl function group combines the hydroxyl
  and the carbonyl functional groups attached to a
  common carbon atom. The carboxyl functional group
  will always be at the end of a carbon chain.
• Carboxyl functional groups form organic (or
  carboxylic) acids. The -OH portion of the
  functional group dissociates in solution,
  donating a H. This dissociation is aided by the
  electronegativity of the O of the carbonyl
  portion of the functional group.

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Amino Group

• The amino function group is - NH2 . The amino
  functional group added to organic compounds forms
  amines. Most amines in living organisms are found
  in molecules which also have carboxyl function
  groups and form the important class of molecules
  called amino acids.
• The amino functional group is a base. The
  nitrogen region of the amino functional group can
  attract a proton (generally attached to a
  hydrogen, thereby removing hydrogen ions from
  solution) resulting in a positive charge (1).

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Sulfhydryl Group

• Sulfur, like oxygen, forms two covalent bonds.
  The sulfhydryl functional group (-SH) is similar
  to the hydroxyl functional group.
• Sulfhydryl functional groups are important in the
  structure of proteins, where the sulfur bonds
  help stabilize the protein's functional
  structure.
• Compounds containing sulfhydryl groups are called
  -thiols.

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Phosphate Group

• Phosphate is a negative ion composed of phosphate
  bonded to 4 oxygen atoms. (PO4), formed by the
  dissociation of phosphoric acid.
• The loss of two hydrogen ions from the acid
  results in the negative charge. One of the oxygen
  molecules of the phosphate functional group bonds
  to the carbon chain.
• Phosphate functional groups are important in
  energy transfer.

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