RT206 FINAL PT1

Radiation

- It is energy that is emitted or transferred in the

form of electromagnetic waves or energetic,

high-speed particles

- It is a propagation of energy through matter or

space

- It is produced by releasing energy of unstable

atoms to become stable or accelerators at

high voltage

- Particulate Radiation

- Electromagnetic Radiation

Forms of Radiation

Particulate Radiation

- It consists of fast-moving subatomic particles with mass and energy

- It is produced by the disintegration of an unstable atom

Alpha particles

-Consists of two protons and two neutrons

(nuclei of Helium atoms) in close

association

-Possess net positive charge

-Emitted during decay of heavy, naturally

occurring radionuclides

Beta Particles

-Small and fast-moving, and more

penetrating than an alpha particle

-Produced only in or near the nucleus of

the atom

Negatron

a negatively charged electron, produced by nuclear disintegration

Positron

A positively charged electron, produced by pair production

Electrons

-Small, negatively charged particles that

can be accelerated to high energy to a

speed close to that of light

Protons

-Positively charged particles and are

relatively massive (2,000 times greater

than an electron)

Neutrons

-Produced if a charged particle is

accelerated to high energy and then

made to impinge on a suitable target

material

-Emitted as a by-product if heavy

radioactive atoms undergo fission

Electromagnetic Radiation

- It is produced by electric and magnetic

disturbances in space that travel in vacuum

with the velocity of light, resulting in a wave-

like motion

- It is known to be massless, and behaves

both as a wave or as a particle (wave-particle

duality)

- Non-ionizing Radiation

- Ionizing Radiation

2 types of Electromagnetic Radiation:

Non-ionizing Radiation

-Found at the long wavelength end of the

electromagnetic spectrum, and may have

enough energy to excite molecules and

atoms

-Cannot ionize matter because its energy

is lower than the ionization potential of

matter

Ionizing Radiation

-Has more energy than non-ionizing

radiation, enough to cause chemical

changes by breaking chemical bonds

-Can ionize matter directly or indirectly

because its energy exceeds the

ionization potential of matter

- Natural-occurring (background) radiation

- Man-made (artificial) radiation

Sources of Radiation

Natural-occurring (background) radiation

- Low levels of ionizing radiation that naturally occur from the surroundings

- As per the United Nations Scientific

Committee on the Effects of Atomic

Radiation (UNSCEAR), terrestrial radiation,

inhalation, ingestion, and cosmic radiation

are the four foremost sources of public

exposure to natural radiation

Man-made (artificial) radiation

- Levels of radiation as a product of human

innovation and activities

- These include nuclear power plants,

accelerators, radionuclide production

facilities, nuclear bombs, medical radiation,

and consumer items

Terrestrial radiation, Inhalation, Ingestion, and Cosmic radiation

Four foremost sources of public exposure to natural radiation acc. to UNSCEAR:

Nuclear power plants, accelerators, radionuclide production facilities, nuclear bombs, medical radiation, and consumer items

Man-made (artificial) radiation examples (6):

- Occupational Exposure

- Medical Exposure

- Public Exposure

Classification of Human Exposure to Radiation:

Occupational Exposure

Obtained as a result of the nature of their work

Medical Exposure

Intentional radiation exposure for diagnostic and therapeutic purposes

Public Exposure

- exposure which might be received from neither work or a medical procedure

- Irradiation

- Contamination

Modes of Human Exposure to Radiation:

Irradiation

A general term that may be used to describe exposure to radiation from any sources

1. External Exposure

2. Internal Exposure

Types of Irradiation:

External Exposure

Indicates that the exposure is due from an external source

Internal Exposure

It may result from inhalation, ingestion or, in some cases, from direct absorption through skin

Contamination

- Undesired presence of radioactive materials

or sources on any substance in

concentrations greater than those which

occur naturally

Activity

- It is the number of radionuclides

disintegrating per second

- It accounts for the "amount of radiation" in a

container

1.Conventional = Curie (Ci)

2.SI = Becquerel (Bq)

Activity (units)

Absorbed Dose

It accounts for the amount of energy deposited in a mass

1.Conventional = rad

2.SI = J/kg

3.Special name = Gray (Gy)

Absorbed Dose (units)

Equivalent Dose

It accounts for the biological effects for different types of radiation

1.Conventional = rem

2.SI = Sievert (Sv)

Equivalent Dose (units)

Radiation Weighting Factor

- It is a dimensionless variable, providing an estimate of relative human hazard from different types of radiation energies

Effective Dose

It measures the biological effects of a particular type of radiation on organs or tissues

1.Conventional = rem

2.SI = Sievert (Sv)

Effective Dose (units)

Tissue Weighting Factor

- It is a dimensionless variable used to

account for the different sensitivities of

different organs and tissues

Radiation Biology

Study of the effects of ionizing radiation on biological tissue

Robert Hooke

He first described the cell as the biological building block

Anton Van Leeuwenhoek

He accurately described a living cell based on microscopic observations

Theodor Schwann and Matthias Schleiden

They both showed that in all plants and animals, cells are the basic functional units (cell theory)

Cells

Are what makes up all living things

• Metabolism

• Growth

• Irritability

• Adaptability

• Repair

• Reproduction

Fundamental life functions occur at the cellular level:

Protoplasm

- A collective term for cytoplasm and nucleus

- Contains organic and inorganic compounds which are

either dissolved or suspended in water

70 - 85%

Protoplasm contains about ___ - ___ % water

Water

Most abundant component of the protoplasm

• Solvent wherein various substances can be

dissolved in

• Transport medium for substances in and out of the

cell

• Lubricant for joints and the digestive tract

• Regulates body temperature through evaporation

• Cushion organs like the brains and lungs

Water is essential to life for several reasons:

Cytoplasm

A colorless material within the cell membrane that comprises all parts of the cell, except the nucleus

Organic compounds

Compounds that contain carbon

Protein

Long-chain macromolecules that consist of linear

sequence of amino acids

Amino acids

building blocks of proteins

carbon, hydrogen, oxygen, nitrogen, and other elements

Protein composes of ...

1. Enzymes

2. Hormones

3. Antibodies

Proteins provide structure and support and also

act as:

Lipids

Organic macromolecules composed solely of

carbon, hydrogen, and oxygen

Lipids

Generally composed of two types of smaller

molecules - glycerol and fatty acid

Lipids

Concentrated under the skin, serving as a thermal

insulator from the environment

Lipids

Serves as fuel for the body by providing energy

stores, but more difficult to extract

Carbohydrates

- Similar to lipids when it comes to chemical

composition but their structure is different

- Known to be the major source of cell energy

Nucleic acids

Also known to be the largest organic molecules

carbon, oxygen, hydrogen, nitrogen, phosphorus

Nucleic acids are organic compounds that contain ...

1. deoxyribonucleic acid (DNA)

2. ribonucleic acid (RNA)

Two principal nucleic acids are important to human metabolism:

deoxyribonucleic acid (DNA)

- Composed of a phosphate group, a

deoxyribose sugar, and paired nitrogenous

bases

- Considered the genetic code for hereditary

characteristics

- Twisted like a spring, producing a double-

helix molecular configuration

- Considered to be a radiation-sensitive target

molecule

ribonucleic acid (RNA)

- can be found in the nucleus

- Involved in the growth and development of the cell, most notably, the protein synthesis

- forms a single helix

- Messenger RNA

- Transfer RNA

Two types of RNA

Inorganic Compounds

Compounds that do not contain carbon

Inorganic compounds

Sodium and potassium are examples of which compound?

Inorganic compounds

- Responsible for maintaining the correct proportion of water in the cell

- Assist in producing cell energy and in conducting nerve impulses

Metabolism

- sums all chemical reactions in a cell,which includes catabolism and anabolism

Cytoplasm

Metabolism takes place in the cells ____

Catabolism

Process of breaking down molecules into smaller

units to release energy or to be used in other anabolic

reactions

Anabolism

Process wherein large molecules are produced from smaller units

Cell membrane

Separate the cell's interior from its exterior

surroundings, and also from adjacent cells

Double layer

Cell membrane is composed of lipids and proteins that are arranged in a ...

Cell membrane

Considered to be semi-permeable, and only lipid-

soluble materials are allowed to be diffused in and

out of the cell

Golgi Apparatus

- Series of flat, membranous layers

Endoplasmic Reticulum

Tubular network that extends from the nuclear membrane to the cell membrane, and it assists in channeling proteins and lipids in and out of the nucleus

Smooth Endoplasmic Reticulum

- has no ribosomes attached to its outer surface

- generally a site for enzyme reactions in steroid hormone production and inactivation

- The part of the cell where many drugs are inactivated

- Serves in storing Ca++ in skeletal muscle cells

Rough Endoplasmic reticulum

- Has numerous ribosomes attached to its outer surface, giving it a rough appearance

- generally found in the cells that are active secretory of proteins like the endocrine and exocrine glands

Mitochondrion

- Double-membranes, oval, or rod-shaped organelles in the cytoplasm where aerobic reactions of cell respiration takes place

- contains enzymes which assist in breaking down carbohydrates, fat, and proteins into energy, and is stored in the cell

- aka the powerhouse of the cell

Ribosomes

- small, dot-like structures, and are the site of protein synthesis

- scattered throughout the cytoplasm or in the endoplasmic reticulum

Centrioles

- Pair of cylindrical organelles located near the nucleus and are perpendicular to each other

- organize the spindle fibers during cell mitosis

Lysosomes

- single-membrane oval or spherical bodies that contain digestive enzymes that digest protein molecules

- Assists in digesting old, worn-out cell parts, dead

Suicide bags

lysosomes aka

Nucleus

- Most vital cell organelle, and is considered the brain for the metabolic activity and cell division

- Floats within the cytoplasm and is surrounded by a double-layered nuclear membrane

- where the DNA is located

Nucleus

Much more sensitive to the effect of radiation than the cytoplasm

Nucleolus

- contained within the nucleus, and is often attached to the nuclear membrane

- controls the passage of molecules, particularly RNA, from nucleus to cytoplasm

Cell proliferation

the act of a single cell or group of cells to reproduce and multiply in number

Mitosis and Meiosis

Two different types of cell proliferation:

Mitosis

Somatic Cells undergo this in order to repair and regrow, creating two identical diploid daughter cells

Interphase

- Period of cellular growth between these divisions, or the non-dividing phase

- chromosomes are not yet visible

G1 phase

- Pre-DNA synthesis phase and the first growth phase of the cell cycle

- resting period before the DNA is replicated

S Phase

- DNA synthesis or replication takes place

- chromosome is transformed, from having two chromatids to four chromatid attached to a centromere with the same DNA content and structure

Late S phase

most radioresistant. Phase

G2 Phase

- Second growth phase of the cell cycle

- Typically known as the post-DNA synthesis phase

- Cell is now preparing to undergo the mitosis phase

Late G2 to mitosis

Most radiosensitive phase

Mitosis

- Considered as the division phase

- DNA slowly takes the form of the chromosomes

Meiosis

Genetic cells undergoing proliferation

Reduction division

Meiosis is also referred to as ...