Rad Bio: Unit 2 Exam

Radiation interacts at what level of organization?

Atomic

Molecules

Atoms bonded together

Atomic Composition

Hydrogen, oxygen, carbon, nitrogen, phosphorus, sulfur and trace elements

Molecular Composition

Water, proteins, lipids-fats, carbohydrates, nucleic acids

What is the only inorganic molecular compound?

Water

Water

Simplest and most abundant inorganic compound in the body; provides form/shape, dissolves materials, functions as transport, maintains body temp, cushion organs and lubricate digestive systems

Proteins

Formed when a sequence of amino acids connected by peptide bonds combine into long, chainlike molecular complexes (macromolecules); essential for growth, construction of new body tissues and repair injured/weakened tissues

Structure of Proteins

C H O N T

Lipids

Composed of glycerol and fatty acids, structural part of the cell membrane; long-term storage of energy, insulate and protect, support organs, assist with growth/development, lubricant joints and assist in digestion

Structure of Lipids and Carbohydrates

C H O

Carbohydrates

Starches and various sugars; short-term storage, cell shape and stability

What are nucleic acids?

DNA and RNA

DNA (Deoxyribonucleic Acid)

Located in nucleus, double stranded macromolecule that contains all hereditary information representing a cell

What is the most critical target molecule for radiation?

DNA

RNA (Ribonucleic Acid)

Cytoplasm of cell, long, single-stranded chain of cells that help DNA translate information (mRNA and tRNA)

Chromosomes

Tiny rod-shapes bodies; only visible during mitosis (cell division)

How many chromosomes do somatic cells have?

46

How many chromosomes do “germ” cells have?

23

DNA Bases

Adenine → thymine

Cytosine → guanine

Cells

Highly specialized to maintain homeostasis, provide energy, oxygen to break down food and water to transport substances

Cytoplasm

Bulk of cell; structure, mass and support

Nucleus

Center of cell; contains DNA

What is the most abundant molecule in the body?

Water

What area of a cell is most critical to proper function and survival?

Nucleus

What type of molecule makes up cell membranes, and provides fuel and insulation?

Lipids

What is the most abundant atom in the body?

Hydrogen

Somatic Cells

All of the cells of the body except sperm and ova; undergoes mitosis

Genetic (germ) Cells

Sperm and ova cells; undergoes meiosis

Cell Proliferation

The act of a single cell or group of cells reproducing and multiplying in number

Mitosis

Two new identical daughter cells that contain exact genetic material  

G1 Phase

Cell growth; longest phase of interphase

S Phase

DNA synthesis; replication to create two daughter cells

G2 Phase

Proteins and RNA molecules created for mitosis

Prophase

Nucleus enlarges, DNA more prominent and begins structural form & centrioles migrate to opposite side of cell and begin to form mitotic spindle  

Metaphase

Mitotic spindle forms between centrioles, chromosomes appear and line along the equator of the nucleus (critical time for damage)

Karotype

Map of chromosomes

Anaphase

Each chromosome split at center, the halves of the chromosomes migrate towards spindles  

Telophase

Chromosomes disappear into a mass of DNA; cytokinesis

Cytokinesis

Nuclear membrane and cytoplasm both divide into two

Meiosis

Reduction in the number of chromosomes from 46 to 23, begins at the end of telophase; ensures zygotes have normal number of chromosomes

Instant death dose

1,000 Gy

Instant death

Massive influx of energy = gross disruption of cell form and structure and DNA; DNA breaks up and cell proteins coagulate  

Reproductive death dose

1-10 Gy

Reproductive death

Permanent loss of ability to reproduce, cell continues to synthesize proteins; damage not able to be transmitted to future generations

Apoptosis (interphase death) dose

1 - several hundred Gy

Apoptosis (interphase death)

Cell dies during interphase without attempting division

Example of apoptosis

Tadpole losing tail

Mitotic (genetic) death dose

1-10 Gy

Mitotic delay (division delay) dose

As little as 0.01 Gy

Mitotic delay (division delay)  

Cell doesn’t divide on time, disrupts ratio of those normally dividing and those note; cells recover from delay and proceed

Interference function

Occurs from various doses, normal cell function can be impaired; repair enzymes can fix damage and cell continues to function

T/F: Molecular damage is reversible.

True

What does molecular repair depend on?

Dose, dose rate, cell sensitivity, cell age and mitosis

Stem Cells

Immature cells

T/F: Mature cells are more radiosensitive.

False

Law of Bergonie and Tribondeau

Age and metabolic rate of tissue being irradiated determines the radiosensitivity of the tissue  

Most sensitive cells

Immature, undifferentiated and rapidly dividing

Blast-

Immature cells

Cyte-

Mature cells

High radiosensitivity (2 – 10 Gy)  

Lymphocytes, erythroblasts and intestinal epithelial (villi) cells

Intermediate (10 – 50 Gy)  

Spermatogonia, epithelial cells, osteoblasts and fibroblasts

Low radiosensitivity

Muscle cells and adult nerve cells

Linear Energy Transfer (LET)  

A measure of the rate at which energy is transferred from ionizing radiation to soft tissue

What is LET measured in?

kEv/_µm

High LET

Alpha radiation; less penetrating, heavy, has a charge, lower energy giving up energy quicker causing a large amount of ionizations and more damage

Low LET

X-rays and gamma rays; very penetrating, no mass or charge, higher energy giving a whole body dose, low number of ionizations with fewer damage

Relative Biological Effectiveness (RBE)

Test radiation refers to test radiation used in specific experiments with specific cells and animal tissues to produce a certain effect

How do you find RBE?

Dose of standard radiation (200-250 kVp) necessary to produce a given effect/dose of test radiation necessary to produce the same effect

RBE for diagnostic x-rays

1

RBE for alpha particles?

20

Low LET = ______ RBE

Low

High LET = ______ RBE

High

Protraction

Dose is delivered constantly but at a lower rate

Fractionation

Dose is delievered in small fractions or increments; lessens radiation effects because cells can undergo repair and recovery between doses

Oxygenation

Tissue is more sensitive to radiation when irradiated in the oxygenated or aerobic state; makes damage more likely to occur and less likely to be repaired

Anoxic

Without oxygen

Hypoxic

Low oxygen

Aerobic

With oxygen

Oxygen Enhancement Ratio

Used to describe the impact of oxygen on radiation effects

How do you find OER?

Dose required to cause biological response without O2/dose required to cause a biological response with O2 

High LET = ______ OER

Low

Low LET = ________ OER

High

At what age are humans more radiosensitive?

Fetus and old age

Radiosensitizers

Increase sensitivity to radiation; ex. vitamin K

Radioprotectors

Compounds that will decrease sensitivity to radiation; must be administered at toxic levels

Radiation Weighting Factor (W_r)  

“Quality factor;” accounts for different types of radiation causing varying biological damage

What does W_^r calculate?

Equivalent dose

What is the equation for EqD?

D x W_r

Tissue Weighting Factor (W_t)  

Accounts for different sensitivity of tissues and organs; best measure for stochastic risk/harm

What does W_t calculate?

Effective dose

What is the equation for EfD?

EqD x W_t

Dose Rate

The rate at which energy is delievered to cells is directly related to its effect

Radiation Hormesis

Theory that suggests that small amounts of radiation is actually good for you because it stimulates hormonal and immune responses to other toxic environments

Increase charge = ______ LET

Increase

Increase penetrability = ________ LET

Decrease

Increase energy = _______ LET

Decrease

Increase ionizations = ______ LET

Increase

Increase LET = _________ damage

Increase

Increase oxygen = _______ sensitivity

Increase

Increase proliferation rate = _________ sensitivity

Increase