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Chapter 2. Life’s Chemical Basis. The Basics. Matter—anything that has mass and takes up space Solid Liquid Gas. The basics. Element—unit of matter than cannot be broken down further by ordinary chemical reactions 92 naturally occurring elements

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Chapter 2

Chapter 2

Life’s Chemical Basis


The basics
The Basics

  • Matter—anything that has mass and takes up space

    • Solid

    • Liquid

    • Gas


The basics1
The basics

  • Element—unit of matter than cannot be broken down further by ordinary chemical reactions

    • 92 naturally occurring elements

    • 98% of weight of any living thing is made up of 6

      • Carbon

      • Hydrogen

      • Oxygen

      • Nitrogen

      • Phosphorous

      • Sulfur


Building blocks
Building blocks

  • Atom—smallest indivisible unit of an element

  • Molecule—multiple atoms of the same element bonded together

  • Compound—multiple atoms of different elements bonded together


Atoms
Atoms

  • Three subatomic particles

    • Protons

    • Neutrons

    • Electrons





Electron orbits
Electron orbits

  • Orbit in “shells”

  • K Shell—2 electrons

  • L Shell—8 electrons

  • M Shell—18 electrons


Periodic chart
Periodic chart

  • Atomic Number=Protons

  • Atomic Mass=Protons + Neutrons


Periodic chart1
Periodic chart

  • Elements in their natural state have neutral charge

    • Positive charge (protons) equals negative charge (electrons)


Isotopes
isotopes

  • Change in the number of neutrons

  • Does not affect charge

  • Carbon-14

    • Atomic Mass = 14 (6 Protons + 8 Neutrons)

  • Radioisotopes in medical diagnosis


ions

  • Change in the number of electrons

  • Affects charge

  • Anion—negative charge

    • More electrons than protons

  • Cation—positive charge

    • More protons than electrons


Bonds
bonds

  • Ionic

  • Covalent

  • Hydrogen




Ionic bonds
Ionic bonds

  • Formed between ions

  • Electrons transfer from one atom to another

  • Opposite charges attract and hold atoms

  • Usually inorganic (acids, bases, salts, etc.)


Covalent bonds
Covalent bonds

  • Atoms share electrons

  • Happens when both have room

  • Usually organic (proteins, carbohydrates, etc.)



Hydrogen bonds
Hydrogen bonds

  • Bond between covalently bonded hydrogen atom & atom in different molecule or different location.

  • Individually weak, but collectively strong.


Water
water

  • Biologically important

  • Makes up 70-90% of living things

  • Unique properties


Water1
water

  • Polar molecule (slight positive & negative charge)

    • Can easily dissolve other polar molecules

    • Hydrophilic

    • Hydrophobic

    • “universal solvent”

    • Cell membranes

  • Temperature stabilizing

    • Keeps cell processes from generating too much heat

    • Evaporation

    • Ice helps insulate


Water2
water

  • “Stick together”

    • Adhesion—water sticks to itself

    • Cohesion—water sticks to other polar molecules

    • Due to polarity & hydrogen bonds


Acidity
acidity

  • pH scale

    • 0-14

    • Based on H+ & OH- molecules

    • Greater H+, lower the pH

    • Each unit is 10-fold change

      • going from pH 6 to 5 increases H+ by 10 times


Acidity1
Acidity

  • Acids

    • Donates H+

    • pH less than 7

  • Bases

    • Accepts H+

    • Releases OH-

    • pH greater than 7

  • Neutrals

    • Release equal numbers of H+ and OH-

    • pH 7.0


Acidity2
Acidity

  • Buffers

    • Biological substances that help regulate pH

    • Release or absorb H+ to keep pH unchanged

    • Ex.—Carbonic Acid, Bicarbonate regulate blood

      H2CO3 + OH- HCO3- + H20

      HCO3- + H+ H2CO3


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