Atoms, Ions, and Molecules Chapter 2 Atoms, Ions, and Molecules

About this Chapter Make up of atoms, ions, & molecules Bonds combine atoms, form molecules Concentrations Biomolecules

Figure 2-1: Atomic structure Atoms and Elements Structure of an atom Protons Electrons Neutrons Mass Charge Nucleus Electron orbitals Elements Essential & trace elements Figure 2-1: Atomic structure

All the Elements Figure 2-2: Periodic table of the elements

Elements of the Body

Elements other than C, H, O and N in Humans Primary Elements (3% of all body weight) Calcium Ca Bones, teeth, muscle and nerve action, blood clotting Phosphorus P Bones and Teeth, DNA, RNA, ATP. Important in energy transfer   Trace Elements (Less than 1 % of body weight altogether) Potassium K Osmotic balance; cell voltage, muscle and nerve action Sulfur S Component of proteins (cysteine) and other organic molecules Sodium Na Osmotic balance; cell voltage, muscle and nerve Chlorine Cl Osmotic balance; cell voltage, muscle and nerve Magnesium Mg Co-factor for many enzymes Iron Fe Hemoglobin and many enzymes Copper Cu Co-factor of many enzymes Zinc Zn Co-factor of many enzymes Manganese Mn Co-factor of many enzymes Cobalt Co Co-factor of many enzymes and vitamin B12 Chromium Cr Co-factor of many enzymes and potentiates Insulin Selenium Se Required for normal liver function Molybdenum Mo Co-factor of many enzymes

Ions and Isotopes Ions have charge Cations + Anions - Isotopes vary mass Neutrons Radioisotopes Unstable nuclei Emit energy -radiation Medical uses as tracers

Ions and Isotopes Figure 2-3: A map showing the relationship between elements, ions, isotopes, and atoms

Four Primary Types of Ionizing Radiation: Alpha Particles Alpha Particles: 2 neutrons and 2 protons They travel short distances, have large mass Only a hazard when inhaled

Four Primary Types of Ionizing Radiation: Beta Particles Beta Particles: Electrons or positrons having small mass and variable energy. Electrons form when a neutron transforms into a proton and an electron or when a proton transforms into a positron and a neutron:

Four Primary Types of Ionizing Radiation: Gamma Rays Gamma Rays (or photons): Result when the nucleus releases Energy, usually after an alpha, beta or positron transition A gamma particle is a photon. It is produced as a step in a radioactive decay chain when a massive nucleus produced by fission relaxes from the excited state in which it first formed towards its lowest energy or ground-state configuration.

Four Primary Types of Ionizing Radiation: X-Rays X-Rays: Occur whenever an inner shell orbital electron is removed and rearrangement of the atomic electrons results with the release of the elements characteristic X-Ray energy

In the medical field, useful X-rays are produced when electrons are accelerated to a high energy. The X-rays themselves are produced by the rapid deceleration of electrons in a target material, typically a tungsten alloy, which produces an X-ray spectrum via bremsstrahlung radiation. Some examples of X-ray energies used in medicine are: superficial X-rays - 35 to 60 keV diagnostic X-rays - 20 to 150 keV orthovoltage X-rays - 200 to 500 keV supervoltage X-rays - 500 to 1000 keV megavoltage X-rays - 1 to 25 MeV

--Superficial radiation therapy (SRT) machines produce low energy x-rays in the same energy range as diagnostic x-ray machines, 20 - 150 kV, to treat skin conditions. --Orthovoltage X-ray machines, which produce higher energy x-rays in the range 200 - 500 kV. These are known as "superficial" or "deep" machines depending on their energy range. Orthovoltage units have essentially the same design as diagnostic X-ray machines. These machines are generally limited to less than 600 kV. --Linear accelerators ("linacs") which produce megavoltage X-rays. The first use of a linac for medical radiotherapy was in 1953 (see also Radiation therapy). Commercially available medical linacs produce X-rays and electrons with an energy range from 4 MeV up to around 25 MeV. The X-rays themselves are produced by the rapid deceleration of electrons in a target material, typically a tungsten alloy, which produces an X-ray spectrum via bremsstrahlung radiation. The shape and intensity of the beam produced by a linac may be modified or collimated by a variety of means. Thus, conventional, conformal, intensity-modulated, tomographic, and stereotactic radiotherapy are all produced by specially-modified linear accelerators. Megavoltage X-rays are by far most common in radiotherapy for treatment of a wide range of cancers. Superficial and orthovoltage X-rays have application for the treatment of cancers at or close to the skin surface. --Cobalt units which produce stable, dichromatic beams of 1.17 and 1.33 MeV, resulting in an average beam energy of 1.25 MeV. The role of the cobalt unit has partly been replaced by the linear accelerator, which can generate higher energy radiation. Cobalt treatment still has a useful role to play in certain applications (for example the Gamma Knife) and is still in widespread use worldwide, since the machinery is relatively reliable and simple to maintain compared to the modern linear accelerator.

Four Primary Types of Ionizing Radiation: Neutrons Neutrons: Have the same mass as protons but are uncharged They behave like bowling balls

--Fast neutron therapy utilizes high energy neutrons typically between 50 and 70 MeV to treat cancer. Most fast neutron therapy beams are produced by reactors, cyclotrons (d+Be) and linear accelerators. Neutron therapy is currently available in Germany, Russia, South Africa and the United States. In the US three treatment centers operate in Seattle, Washington, Detroit, Michigan and Batavia, Illinois. --Radiation therapy kills cancer cells in two ways depending on the effective energy of the radiative source. --Low Linear Energy Transfer radiation damages cells predominantly through the generation of reactive oxygen species free radicals. The neutron is uncharged and damages cells by nuclear interactions. Malignant tumors tend to have low oxygen levels and thus can be resistant to low LET radiation. This gives an advantage to neutrons in certain situations.

Proton Therapy   One of the most exciting advances in the fight against cancer – proton therapy – is coming soon to Miami Cancer Institute. When it opens in 2017, the Proton Therapy Center will be the only center of its kind in the region and one of only 14 in the United States. An advanced form of radiation treatment, proton therapy spares healthy tissue and eliminates many of the side effects of conventional radiation treatment (also known as photon or external beam radiation). It shoots from 360 degrees around the patient. Miami Cancer Institute will feature three proton treatment rooms with the newest form of proton therapy – called pencil-beam scanning – the most precise and accurate way to deliver radiation to a tumor. While traditional X-rays pass through healthy tissue and organs on their way in and out of the body, protons travel through the body and release most of their energy inside a tumor. Using proton therapy reduces the risk of damage to bones and soft tissues and decreases the odds of other tumors later in life, which makes it particularly good for treating childhood cancers.

Four Primary Types of Ionizing Radiation Alpha particles Beta particles Gamma rays (or photons) X-Rays (or photons) Neutrons

How this can be dangerous How we can protect ourselves - Types will be discussed later Ionization Ionizing radiation is produced by unstable atoms. Unstable atoms differ from stable atoms because they have an excess of energy or mass or both. Unstable atoms are said to be radioactive. In order to reach stability, these atoms give off, or emit, the excess energy or mass. These emissions are called radiation.

Types or Products of Ionizing Radiation - Symbols Types or Products of Ionizing Radiation   or X-ray neutron

DNA and Radiation

Ionizing Radiation at the Cellular Level Causes breaks in one or both DNA strands or; Causes Free Radical formation

Commonly Transported Radioisotopes Americium-241= Diagnose thyroid disorders, smoke detectors. Cesium-137= Cancer treatment. Iodine-125,131= Diagnosis & treatment liver, kidney,heart, lung and brain. Technetium-99m=Bone and brain imaging; thyroid and liver studies; localization of brain tumors.

rad 1 rad = 1 Roentgen - 3 bullets will transition 1 by 1 - 1953 - dose relates to an irradiated medium - 1 Roentgen equivalent to 95 ergs/g of tissue - gamma vs. neutron (LET)

rem Roentgen Equivalent Man The unit of dose equivalent for any type of ionizing radiation absorbed by body tissue in terms of estimated biological effect - Unit of dose equivalent Dose in health record is in units of rem 1 rem = 1 Roentgen 1 Sievert (Sv) = 100 REM 1 mSv = 100 mREM - 5 bullets will transition 1 by 1 - For biological damage (tissue) purposes

Quality Factor (Q) The specific value that accounts for the ability of different types of ionizing radiation to cause varying degrees of biological damage X-rays, gamma rays, & beta particles 1 Neutrons & High energy protons 10 Alpha Particles 20 - Table Pg. 5 - Function of LET - Higher LET - Higher Q

Units of Radioactivity Curie (Ci) = 2.22 E12 dpm or 3.7E10 dps Becquerel (Bq) = 1 dps Maximum Dose/year = 5 REM or 50 mSv Maximum Dose/year for Declared Pregnant Woman & Minors= 0.5 REM or 5 mSv           

Half Life Calculation

*Effective dose equivalent Annual Dose Limits External/Internal Exposure Limits for Occupationally Exposed Individuals   Adult ($18 yrs) Minor (< 18 yrs) Whole body* 5000 mrem/yr 500 mrem/yr Lens of eye 15000 mrem/yr 1500 mrem/yr Extremities 50000 mrem/yr Skin Organ *Effective dose equivalent

Dose Response Relationships 0-150 rem—No or minimal symptoms 150-400 rem—Moderate to severe illness 400-800 rem—Severe illness deaths start above 500 rem Above 800 rem—Fatal ***Acute whole body doses 0-150 Perhaps increased cancer with long latency\\\150-400 increased cancer risk---400-800 GI damage at higher rates

Your Annual Exposure Activity Typical Dose Smoking 280 millirem/year Radioactive materials use  in a UM lab <10 millirem/year Dental x-ray 10 millirem per x-ray Chest x-ray  8 millirem per x-ray Drinking water  5 millirem/year Cross country round trip by air  5 millirem per trip  Coal Burning power plant 0.165 millirem/year 

Estimated Exposure To The National Population Between 320 – 360 mr/yr