The Chemical Level of Organization

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The Chemical Level of Organization

• Atoms
• Atomic Structure
• Electron Shells, losing/gaining electrons
• Ions
• Molecules, their formation through bonds
• Chemical Bonds (how, why, and types)
• Macromolecules
• 4 major macromolecules

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Elements Atoms
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Elements

• Different kinds of matter (material) that have
  distinct (chemical) properties
• Examples
• gold
• carbon
• hydrogen
• sodium
• nitrogen
• calcium
• oxygen

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many different object/pictures
5 basic shapes
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Atoms

• Smallest unit/piece of an element (matter) that
  still has the properties of that element.

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The structure and components of an atom
--Neutral
--positive
--negative
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Electron Shell (orbital)
Electron Shell (orbital)
Nucleus
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Different elements are made of atoms with
different numbers of protons and electronsthat
is why each element has its own unique set of
properties
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Element Number of protons Number of electrons of Body by Weight
Hydrogen 1 1 9.5
Carbon 6 6 18.5
Nitrogen 7 7 3.3
Oxygen 8 8 65.0
Sodium 11 11 0.2
Sulfur 16 16 0.3
Chlorine 17 17 0.2
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Valence Shells

• outermost shell of atom valance shell
• Atoms are most stable when the outer shell is
  filled, or emptied.

Valance shells
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Electron shells of common elementsValance in red
1st shell 2nd shell 3rd shell 4th shell
Hydrogen 1
Carbon 2 4
Nitrogen 2 5
Oxygen 2 6
Sodium 2 8 1
Chlorine 2 8 7
Potassium 2 8 8 1
calcium 2 8 8 2
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Behavior of atoms and outer electron shells

• Atoms want to have completely emptied or
  completely filled outer electron shells.
• Atoms will gain, lose, or share electrons to fill
  or empty their outer shells.
• This is the basis for chemical bonds and the
  formation of ions

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electron shell orbital valence shell
regions that hold electrons
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Formation of ions
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Gaining or Losing Electrons

• Gaining Electrons
• If the outer shell is almost full, gaining
  electrons is likely to happen

• Losing Electrons
• If the outer shell is almost empty, losing
  electrons is likely to happen

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Note that both of these events will result in the
creation of an ion.
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• Atoms lose an electron and become a positive ion.

• Atoms gain electrons and become a negative ion.

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(not from your text)
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Functions of Ions

• Generate Electricity (membrane potentials)
• e.g., neurons of your brain and nervous system
  (sodium, potassium, and calcium)
• Regulate/initiate cellular events
• e.g., help initiate muscle contraction, release
  of neurotransmitters, expression of DNA, activate
  enzymes (calcium), blood clotting
• Building materials
• e.g., Calcium (and phosphate) is part of bones
• Regulate pH/acidity
• HCO3- (bicarbonate ion)

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CHEMICAL BONDING AND MOLECULES
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CHEMICAL BONDING

• Two or more atoms can bind together to form a
  molecule.
• There are 3 major types of chemical bonds
• Ionic Bonds
• Covalent Bonds
• Hydrogen Bonds

Create molecules
do NOT create molecules
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Ionic Bonds
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Formation of an Ionic Bond

• Ionic bonds are usually formed when two atoms
  happen to be in close proximity and exchange
  electrons and become oppositely charge ions.
• The atoms are then held together by the
  attraction of opposite charge
• Strength

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Covalent Bonds
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• When an electron pair is shared, both atoms get
  to count the other atoms electron as if it was
  part of their own valance shell.

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• Covalent Bonds
• Atoms share electrons
• Strength

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Polar and Non-polar Bonds/Molecules

• Non-Polar electrons are shared equally
• the entire molecule is neutral and uniformly
  charged.
• Tends to mix well with other non-polar substances
• Dont mix well with water
• Polar electrons are not shared equally
• then entire molecule is neutral overall, but has
  regions/areas that are or charged
• Tends to mix and dissolve well with other polar
  things
• LIKES WATER/mixes with water

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Polar (and charged)
Hydrophilic
Water soluble
nonpolar
Not water soluble (lipid soluble)
Hydrophobic
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Hydrogen bonds
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Hydrogen Bonds

• Are attractive forces between a hydrogen and an
  oxygen or a hydrogen and a nitrogen
• NOT based on electron transfer or sharing
• Hydrogen bonds can exists between
• 1. two different molecules--resulting in their
• being held together.
• two different parts of the same molecule
• resulting in the bending/folding of the
  molecule.
• But hydrogen bonds dont create molecules the way
  that a covalent or ionic bond does.

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Comments on H-bonds

• individual hydrogen bonds are weak, the
  collective influence of many hydrogen bonds can
  be significant
• The bending of molecules with hydrogen bonds
  creates the final 3D shape of proteins
• Form between water molecules
• Hold DNA strands together
• H-bonds are weak bond formed between two polar
  molecules based on opposite charges attracting
  (not based on electron sharing)