2 - The Chemistry of Life

2 - The Chemistry of Life - Chapter2:TheChemicalContext...

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Chapter 2:  The Chemical Context Of Life 11:37 called compounds o Matter:  anything that takes up space and has mass Mass:  the amount of matter in an object Weight:  how strongly that mass is pulled by gravity Made up of  elements:  a substance that cannot be broken down to other substances by  chemical reactions 92 elements Compound:  a substance consisting of 2 or more different elements  combined in a fixed ratio (e.g. H 2 O) o Essential Elements of Life 25/92 natural elements are essential to life ** C, O, H, N ( 96% of all life ) Trace elements:  those required by an organism in only minute  quantities E.g. iron (needed to all organisms) iodine (essential to vertebrates – for thyroid gland)  deficiency   goiter Parathyroid generates calcium 2.2: An element’s properties depend on the structure of its atoms Atom:  the smallest unit of matter that still retains the properties of an  element Subatomic Particles
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o Neutron mass   Proton mass ( 1.7 x 10 -24  g ) o Measure of mass of subatomic particles   Daltons o Atomic Number:  number of protons (element identity) o Mass Number (Atomic mass) =  protons + neutrons Isotopes o Same proton no. but Different neutron no. o Identical chemical reactions o Carbon-12: most common (6 neutrons) o Radioactive isotope:  An isotope that is unstable; the nucleus decays  spontaneously, giving off detectable particles and energy Change in no. of protons   another element E.g. Carbon-14   Nitrogen
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Application Date fossil relics of past life Tracers: to follow atoms through metabolism PET scanners Concentration of radioactive material in urine Hazards Damages cellular molecules Nuclear fallouts  The Energy Levels of Electrons o Atoms are mostly empty space o Only electrons are directly involved in the chemical reactions o Energy:  the capacity to cause change (e.g. by doing work) Potential Energy:  the energy that matter possesses because of its  location or structure Matter has a tendency to move to the lowest possible state of  potential energy Further the electrons are from the nucleus, the greater the potential  energy Energy levels:  the different states of potential energy that electrons  have in an atom Energy shells:  An energy level of electrons at a characteristic  average distance from the nucleus of an atom
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o Electron Configuration: the distribution of electrons in the atom’s 
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This note was uploaded on 01/31/2011 for the course BIO 101 taught by Professor Nil during the Spring '03 term at Hanken.

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2 - The Chemistry of Life - Chapter2:TheChemicalContext...

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