Chemistry of life

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Chemistry of life
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Matter

• Takes up space and has mass
• Exists in different forms
• Solid
• Liquid
• Gas

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Elements

• Matter is composed of elements
• Common elements found in living matter include
• Carbon(C) , Hydrogen (H), Nitrogen (N), Oxygen
  (O), Phosphorus (P), sulfur (S)(98 )

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Other elements

• Other elements found in cells include
• Sodium (Na)
• Magnesium (Mg)
• Chlorine(Cl)
• Potassium (K)
• Calcium (Ca)

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Elements are composed of atoms

• Atoms are the smallest units of matter which
  maintain the properties of that element.
• Atoms are composed of subatomic particles
• Protons (), Neutrons, Electrons (-)

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Atomic symbol

• First letter, or first two letters
• H for hydrogen, C for carbon, Ca for calcium

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Atomic weight (mass) and number

• Superscript atomic mass which is equal to
  weight of neutrons and protons
• Subscript atomic number which is the number of
  protons
• 12C6 The atomic mass of carbon is 12 and the
  atomic number of carbon is 6

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Isotopes

• Have the same number of protons but different
  number of neutrons.
• Isotopes of the same element behave the same in
  normal chemical reactions
• 14C is a radioactive isotope of carbon.

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Isotopes are useful

• 14C is used to date old material containing
  organic matter.
• Isotopes are used in medicine for treatment of
  cancers and for detection of labeled chemicals

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Energy

• Energy is the ability to do work
• Potential energy is energy due to position or
  stored energy
• Electrons have different amounts of energy

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Bohr model of atom

• The nucleus is in the center of the atom and
  contains neutrons and protons
• The electrons occupy energy cloud around the
  nucleus

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Energy and atomic structure

• The electrons in the inner most shell (K) have
  the LEAST amount of potential energy
• The electrons in the outer shells (L,M) have
  more potential energy

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not all electrons are equal

• electrons can have different amounts of potential
  energy
• When atoms in plants absorb photons it causes
  electrons to gain potential energy causing the
  electrons to go a outer shell.

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Atomic configurations

• The first shell (K) can only hold two electrons
• The second shell can hold eight electrons
• Electrons fill from the inner shell out
• If the outer shell is full the atom is
  non-reactive

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Chemical formulas

• H2O is water. The formula indicates that there
  are two hydrogen atoms bound to a oxygen atom.
• C6H12O6 is the formula for glucose (hexose- six
  carbon sugar)

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Equations are balanced

• 6CO2 6 H2O? C6H12O6 6O2
• the chemicals listed on the left are called
  reactants and the ones on the left are called
  products
• Balanced means that there are 6 carbons in the
  reactants and 6 carbons in the products, the
  oxygens and hydrogens are also balanced.

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Compounds

• Compounds consists of elements bound together
• For example O2 is a compound as is (water) H2O.
• The smallest unit of a compound is a molecule

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water is different

• Compounds have emergent properties. For example
  water behaves chemically very different than
  Hydrogen and different from Oxygen.

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Molecule

• The smallest unit of a compound is called a
  molecule

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Bonds

• Chemical bonds hold together atoms in a compound
• There are three major classes of bonds
• Ionic, covalent and hydrogen

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Ionic bonds

• The electrons in the outer shell contribute to
  form ionic bonds
• An ionic bond forms when one atom donates an
  electron and the other one accepts an electron
• NaCl (sodium chloride) forms ionic bonds

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Ions

• Are atoms which have a charge
• When sodium losses an electron it becomes Na
• When chlorine gains an electron it becomes Cl -
• Salts are example of compounds which have ionic
  bonds

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Covalent bonds

• The electrons in the outer shells are shared
• Example H2, O2, CH4
• Covalent bonds can also be double (CC) or triple

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Polar molecules

• Water is an example of a polar molecule, the
  oxygen end is slightly negative and the hydrogen
  ends are slightly positive

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Hydrogen bonds

• Polar compounds such as water for hydrogen bonds
• Polar bonds form in large molecules such as
  proteins and nucleic acids

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Water is unique

• Living organisms are mostly water (70-90)
• The unique properties of water are due to
  hydrogen bonds between molecules of water
• Water has a high heat of vaporization
• Water has a high specific heat (resists changes
  in temperature)

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Water, cont.

• Water is a excellent solvent
• Water molecules are cohesive and adhesive
• Water has a high surface tension
• Ice is less dense than water, so lakes freeze
  from top down. (ice floats)

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pH, acids, bases

• H2O?H OH- water ionizes.
• H is the hydrogen ion OH- is the hydroxide ion

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Acids

• Have a high hydrogen ion concentration
• Acids dissociate in water and release hydrogen
  ions
• Inorganic acid is HCl (hydrochloric acid)

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Bases

• Example NaOH sodium hydroxide is basic
• Bases take up hydrogens or release hydroxide ions

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pH scale

• is the negative log of the hydrogen ion
  concentration
• 1.0 x 10-7 pH7 which is neutral
• 1.0 x 10-3 pH3 which is acidic
• 1.0 x 10-9 pH9 which is basic (alkaline)

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Buffers

• Buffers help to stabilize pH
• An example of a buffer system is NaHCO3 (sodium
  bicarbonate) and carbonic acid. Buffers consist
  of a weak acid and the salt of that acid.
• Buffers 'absorb' excess H ions or excess
  hydroxide ions