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The Chemical Basis of Life
- (^) Why are we studying chemistry in a biology course???
- (^) At the base of the hierarchy of life are atoms and molecules!
- (^) Many biological processes take place on a molecular level Biosphere Ecosystem Florida coast Community All organisms on the Florida coast Population Group of brown pelicans Nucleus Nerve Spinal cord Cell Nerve cell Tissue Nervous tissue Organ Brain Organelle Nucleus Molecule DNA Atom Organism Brown pelican Organ system Nervous system Brain
- (^) The food we eat is made up of chemical elements, many of which are essential to life http://www.dennysbeerbarrelpub.com/
Elements, Atoms and Molecules
- (^) The remaining 4% is made up of
- (^) Calcium (Ca) bone formation
- (^) Phosphorus (P) DNA synthesis
- (^) Potassium (K) cell signaling, nervous system
- (^) Sulfur (S)
- (^) Sodium (Na)
- (^) Chlorine (Na)
- (^) Magnesium (Mg) …..mostly
Elements, Atoms and Molecules
- (^) What about the remaining 0.01%?
- (^) Trace elements are present in trace , or minute quantities, but are extremely important
- (^) Examples of trace elements include:
- (^) Iron (Fe) – hemoglobin, binds oxygen
- (^) Copper (Cu) – enzymes, electron transport
- (^) Fluorine (F) – prevents tooth decay, added to municipal water
- (^) Iodine (I) – thyroid enzymes (deficiency goiter); “iodized salt”
Elements, Atoms and Molecules
- (^) Not all elements are good for us!
- (^) Mercury – toxic to humans; mercury poisining
- (^) Mercury is concentrated in fish, especially of higher trophic level (e.g., swordfish, tuna, shark); accumulates and remains in body
- (^) Leads to tremors, impaired cognitive (thinking) skills, sleep disturbance
- (^) The human body rids mercury via nails and hair
- (^) The “Mad Hatter”
Elements, Atoms, and Molecules
- (^) An element can combine to form compounds
- (^) A compound is a substance consisting of 2 or more different elements - (^) Much more common than elements - (^) Sodium chloride (NaCl; “table salt”) = 1 part sodium and 1 part chlorine - Water (H 2 O) = 2 Hydrogen atoms and 1 Oxygen atom - (^) Proteins are compounds (C,H,O,N, S); different arrangement and #s of atoms different proteins
Electron cloud Protons 6e– “Nucleus” Mass number = the sum of protons and neutrons in the nucleus. In this case, Carbon’s mass number is 12 (6p +6n) 6 6 Electrons Neutrons 6 Example: Carbon Atom Atomic number = the number of protons ; each element has Its own unique number of Protons. In this case, Carbon’s atomic number is 6 (6p)
Isotopes
- (^) All atoms of an element have the same atomic number (number of protons), but some atoms of an element may differ in mass number (number of protons + number of neutrons) = different isotopes of an element
- (^) Different isotopes of an element have the same number of protons and electrons and so behave identically chemically, but have different numbers of neutrons
Isotopes
- (^) Stable isotopes do not decay; they tend to maintain their neutrons
- (^) Radioactive isotopes do decay; the nucleus decays spontaneously, releasing particles and energy (gamma rays and/or subatomic particles)
- (^) Radioactive isotopes (“radioisotopes”) exist naturally, but may also be created artificially
Radioisotopes
- (^) Radiation from decaying isotopes can be hazardous to your health! - (^) Causes cellular damage (damages cellular molecules) - (^) The particles and energy thrown off by radioactive isotopes break chemical bonds and can also cause abnormal bonds to form; cancer, DNA damage - (^) Uranium (from rocks) naturally decays into Radon (a radioactive gas); basements can have high levels; lung cancer
Elements, Atoms and Molecules
- (^) The electron arrangement determines the chemical properties of an atom
- (^) Electrons are arranged in shells, or energy levels, called energy shells
- (^) The number of electrons in the outermost shell determines the chemical properties of the atom
Magnesium Lithium Hydrogen Sodium Beryllium Aluminum Boron Silicon Carbon Phosphorus Nitrogen Sulfur Oxygen Chlorine Fluorine Argon Neon Helium
The first 18 elements in the
Periodic Table
Atoms whose shells are incomplete tend to interact with other atoms to gain, lose, or share electrons
**Na Sodium atom Transfer of electron Cl Chlorine atom Na+ Sodium ion Cl– Chloride ion Sodium chloride (NaCl)
Formation of an ionic bond
Covalent bonds
- (^) Two atoms may also share one or more pairs of outer-shell electrons
- (^) When atoms share outer shell electrons, they form covalent bonds
- (^) *Atoms formed by ionic or covalent bonds form a molecule
- (^) These bonds are very strong
- (^) A molecule can consist of 2 different elements, or 2 atoms of the same
