BIOL 2010 Lecture Notes - Lecture 2: Ionizing Radiation, Beta Particle, Covalent Bond

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Published on 2 Feb 2017
School
TNTECH
Department
Biology
Course
BIOL 2010
Professor
CHAPTER 2
Chemistry of Life
Humans are made of elements
o Predominately made of 3 elements but even the trace of elements is important
for normal physiology
Some are classified as minerals
o Inorganic elements extracted from the soil by plants and then moved up from
the food chain
Ca, P, Cl, Mg, K, Na, S, I, Fe, Mn, Zn, Cu
Elements are made of atoms...
o And atoms are made of...
Protons
Positive charge
Number determines which element is which
Weight of 1 amu
Neutrons
Neutral charge
Number can vary leading to isotopes
Weight of 1 amu
Electrons
Negative charge
Number normally equals the number of protons
Weight of egligile
o protons and neutrons found in the nucleus while electrons are found in orbits
called shells
Bohr model of atoms is overly simplistic but it will work for us
Isotopes
o Chagig the ue of eutos does’t affet the odig ehaio of the
atoms
It is the valence electrons that matter there
Does affect their physical behavior and they may be unstable
Stable isotopes do not decay
Radioactive isotopes (radioisotopes) do
o Friend or foe?
Both
Radiation (the emission of energy as electromagnetic waves)
Light, radio waves are all types of low energy radiation that do not
cause harm
Ionizing radiation has a high enough energy to cause electrons to be
ejected
Forms ions (hence the name)
Three kinds of radiation produced by nuclear decay
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o Alpha particles
o Beta particles
o Gamma particles
Half-lives of Radioactive Chemicals
o Radioactive materials decay (change from one element to another)
o Each radioisotope has a specific half-life
Physical half life
o Biological half-life refers to how long it will stay in the body
Length of time can be different than physical half-life because it depends
on how the ion behaves in the body
Example: Cesium-137 has a physical half-life of 30 years but a
biological half-life of 17 days
o Chemically, it acts like potassium in the body and is easily
excreted
Radiation Exposure
o Alpha and beta sources are relatively harmless in small doses and as long as the
ion is outside the body
Ingesting them can cause issues
o Sieverts (Sv, SI unit for radiation) take into account the type and intensity of
radiation on the body
Single doses of 5 Sv or more are usually fatal
o Average person receives doses of radiation of 2.4 mSv (so 0.0024 Sv) per year
from natural sources
Another 0.6 mSv from artificial sources like your smoke detector and TV
o Guidelines are in place for workplace exposure to radiation
Healthcare workers who deal with CTs, X-rays, etc can get no more than
50 mSv per year
Ions
o Ions are elements or molecules that differ in their number of electrons and
protons
o The element/molecule either gained electrons or lost electrons in the ionization
process
o Charge on the ion is called valence
Electrolytes
o Acids, bases, and salts
All of these ionize in water
Conduct electrical current
Allows for the usage for EKGs, EEGs, and other physiological
instrumentation
Important because:
The reactivity of electrolytes depends on whether or not they are
ionized
o Ionized forms are the only ones that are biologically active
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The ifluee the osoti pessue of the od’s aious fluids
Their electrical effects play a role in muscle contraction and
nervous system conduction
Free Radicals
o Produced by both natural and unnatural means
Naturally made in some metabolic reactions
ATP production in mitochondria
Certain WBCs use them to kill bacteria
Radiation can cause the formation of them
UV radiation (naturally) and X-rays (unnaturally)
Molecules
o Combining elements results in the formation of molecules
Same element? Molecule of that element (Ex. O2)
Different elements? Compound (Ex. CH4)
o Molecular formulae can be helpful in identifying particular compounds but you
have to be careful about structural isomers
o Molecular weight is the sum of the atomic weights of its atoms
o “haig of eletos does’t hae to e eual
o The most electronegative atom (or molecule) in a compound will draw the
electron density
o Electrons equally shared?
Non-polar covalent bond
o Electrons not equally shared?
Polar covalent bond
Hydrogen Bonding
o Intermolecular force
occurs between a polar covalently bonded molecule where that molecule
had a hydrogen atom attached to a very electronegative atom (usually O,
N, or F)
the hydrogen is attracted to another electronegative atom or negative
ion in solution
Van der Waals Interactions
o Brief attraction between neutral molecules
o Very weak
o Occurs when electron density randomly shifts in one molecule causing a shift in
another
Importance of water in the human body
o Water is involved in most of the mixtures in our bodies
o Several important properties for water (all our due to its polarity)
Cohesion- tendency of molecules of the same time to cling together
Adhesion-tendency of molecules of different types to cling together
Chemical reactivity- can ionize other molecules as well as it ionizes itself
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Document Summary

Chemistry of life: predominately made of 3 elements but even the trace of elements is important for normal physiology. Inorganic elements extracted from the soil by plants and then moved up from the food chain. Ca, p, cl, mg, k, na, s, i, fe, mn, zn, cu. Elements are made of atoms: and atoms are made of Number normally equals the number of protons. Weight of (cid:862)(cid:374)egligi(cid:271)le(cid:863: protons and neutrons found in the nucleus while electrons are found in orbits called shells. Bohr model of atoms is overly simplistic but it will work for us. Isotopes: cha(cid:374)gi(cid:374)g the (cid:374)u(cid:373)(cid:271)e(cid:396) of (cid:374)eut(cid:396)o(cid:374)s does(cid:374)"t affe(cid:272)t the (cid:271)o(cid:374)di(cid:374)g (cid:271)eha(cid:448)io(cid:396) of the atoms. Does affect their physical behavior and they may be unstable. It is the valence electrons that matter there. Radiation (the emission of energy as electromagnetic waves) Light, radio waves are all types of low energy radiation that do not cause harm.