Rad Bio - Cell Biology (Unit 1-2)

Body Composition (5 Primary Molecules)

• 80% Water

• 15% Protein

• 2% Lipids

• 1% Carbohydrates

• 1% Nucleic Acid

Macromolecules

Large molecules of thousands of atoms.

Organic Molecules

• Proteins, lipids, carbs

• Life supporting, contain carbon

Water (3)

• Most abundant

• Delivers energy to DNA

• Essential to sustaining life, serves as the transport vehicle for materials the cell uses or eliminates.

_________ is the most radiosensitive target molecule.

DNA

Protein

• Provides structure, support

• Muscles are high in protein and are the most abundant tissue in the human body.

Life-Sustaining Role of Water in the Human Body (8)

• Acts as the medium in which acids, bases, and salts are dissolved.

• Functions as a solvent by dissolving chemical substances in the cell.

• Functions as a transport vehicle for material the cell uses or eliminates.

• Maintains a constant body core temperature of 98.6

• Provides a cushion for vital organs, such as the brain and lungs

• Regulates concentration of dissolved substances

• Lubricates the digestive system

• Lubricates skeletal articulations (joints)

Carbohydrates

• In some cells and tissues to provide stability

• Provides fuel for metabolism

2 Primary Nucleic Acids

• DNA

• RNA

DNA

Command center for cell function and contains all hereditary info in germ cells.

RNA

Involved in development of cell through protein synthesis.

DNA is made of two linked strands that wind around each other to resemble a twisted ladder also known as a _________________.

Double helix

Each strand of DNA has a backbone of alternating sugars (___________) and phosphates.

Deoxyribose

The 4 organic bases attached to the sugar on a DNA strand are:

• Adenine

• Guanine

• Thymine

• Cytosine

Cell

Basic unit of any living thing.

There are roughly _________ cells in the average human.

100 trillion

Principle Structures Within the Cell (3)

• Nucleus

• DNA

• RNA

Nucleus

Contains DNA, RNA, protein, and water surrounded by a cell membrane.

The ____ contains genetic information and controls cell division.

DNA

The _____ is located principally in the cytoplasm but is also found in the nucleus.

RNA

mRNA

Carries genetic info from DNA to aid in protein synthesis in the ribosomes.

________ are essential for growth, the construction of new body tissue, and repair of injured/debilitated tissue. They may also function as hormones and antibodies.

Proteins

Cytoplasm

“Storage bad”; jelly-like material that surrounds inner structures; comprises majority of cell.

Endoplasmic Reticulum

“Highway” channels that allow the nucleus to communicate with the cytoplasm.

Mitochondria

Bean-shaped “powerhouse of the cell” that digests macromolecules to produce energy.

Ribosomes

“Protein factories” read the “message” from RNA and manufacture proteins that cells require by using the blueprints provided by mRNA.

Lysosomes

“Garbage bags” contains enzymes that digest unwanted cellular fragments.

Secretory Channel

Releases proteins or other molecules when stimulated by a nerve or hormonal signal.

Which of the following are essential functions of water in the human body? (select all that apply)

• Lubricates skeletal articulations

• Produces enzymes used to breakdown cell materials

• Provides cushion for vital organs

• Regulates concentration of dissolved substances

• Maintains body temperature of 96.8 F

• Lubricates skeletal articulations

• Provides cushion for vital organs

• Regulates concentration of dissolved substances

The ___________ keeps the cell clean of unwanted cellular waste, but sometimes may rupture and digest the cell it resides in leading to cell death.

Lysosome

Cell Proliferation

Act of a single cell of group of cells to reproduce and multiply in number.

Interaction between x-rays and DNA may be capable of disrupting ______________.

Cell proliferation

Genetic Cells undergo ___________.

Somatic Cells undergo ___________.

• Meiosis

• Mitosis

Cells undergo mitosis for purposes of __________, __________, and ___________.

• Reproduction

• Repair

• Growth

The 2 phases of the cell cycle are ________ (__%) and _________ (__%).

• Interphase

• 90

• Mitosis

• 10

Cancer is uncontrolled ___________.

Mitosis

What are the 4 stages to Mitosis (Division phase)?

• Prophase

• Metaphase

• Anaphase

• Telophase

The processes occurring during interphase are:

• Cell growth

• DNA replication

• Daily cell functions

The 3 steps of interphase are:

• G1

• S (DNA synthesis)

• G2

Cells are particularly radiosensitive during ______ and ________.

• Late G2

• Mitosis

DNA replication occurs during the ___ phase, which is a less radiosensitive stage of the cell cycle.

S

Meiosis is similar to mitosis, except no _______________ occurs in telophase.

DNA replication

Meiosis (Reduction Division)

1. Starting cell has 46 chromosomes

2. Cell PMATs into 2 new cells, each containing 23 chromosomes.

3. 2 new cells PMAT again into 4 new cells, but this time no replication of DNA or chromosomes.

In meiosis, the number of chromosomes in the daughter cell is ______ the number of chromosomes in the parent cell.

Half

Mitosis produces _______ cells with _____ chromosomes each.

• 2

• 46

Meiosis produces ______ cells with ______ chromosomes each.

• 4

• 23

Crossing Over in Meiosis

• During Prophase 1, some chromosomal material is exchanged between chromatids.

• Results in changes in inheritable traits.

The process of meiosis from once cell produces ______ cells with _____ chromosomes each.

• 4

• 23

Radiation Biology

Branch of biology concerned with effects of ionizing radiation on living systems.

Radiobiology's first area of focus is the sequence of events occurring after the ______________ from ionizing radiation.

Absorption of energy

Radiobiology's second area of focus is the action of the living system to compensate for __________________.

Consequences of energy assimilation/absorption.

Radiobiology's 3rd area of focus is _________ to the living system that may occur from irradiation.

Injury

Ionizing radiation damages living systems by ______________ from the atoms comprising these systems.

Removing electrons

Altered atoms do not __________ in molecules.

Bond properly

LET (Linear Energy Transfers)

Average energy deposited per unit length of track.

LET from diagnostic x-rays to soft biologic tissue is estimated to be _______________.

3 keV/μm

As LET increases, the chance of significant biologic response in radiosensitive DNA ___________.

Increases

Low-LET radiation is ____________________.

Electromagnetic radiation (EMR)

Free Radicals

Molecules that cause damage to biologic tissue; chemically reactive due to unpaired valence (outermost) electrons.

Single-Strand DNA Breaks

Much less likely; repair enzymes usually reverse the damage.

Relative Biologic Effectiveness (RBE)

The effect of high LET leading to higher probability of interaction with biologic tissue.

RBE and LET of Diagnostic X-rays

• 1 RBE

• 3 LET

As LET increases, RBE _____________.

Increases

Oxygen Enhancement Ratio (OER) Definition

Tissue radiation response in relation to the level of tissue oxgenation.

Oxygen Enhancement Ratio (OER) Equation

= dose required to cause an effect without oxygen ÷ dose required to cause that effect with oxygen.

Tissue is most sensitive to radiation when ___________ and least sensitive when ______________.

• Oxygenated

• Devoid of oxygen

Cancerous tumors often contain ___________________ which have little/no oxygenated blood supply. They are ____________________ and tougher to treat with radiation therapy.

• Anoxic/hypoxic cells

• More radioresistant

If a large portion of ________ cells are affected, entire body processes can be disrupted.

Somatic

If _______________ cells are affected, damage may be passed on to future generations as ________________.

• Genetic (reproductive)

• Genetic mutations

Direct Radiation

When ionizing particles interact with a vital target macromolecule (i.e. DNA) causing them to become abnormal structures.

Indirect Radiation

When ionizing particles interact with a water molecule. Creates free radicals that produce toxic substances and can migrate to a target molecule and cause damage.

Radiolysis

Dissociation of water molecules by ionizing radiation.

Target Theory

States that when a vital macromolecule or target such as cell DNA is directly or indirectly inactivated by exposure to radiation, the cell will die (apoptosis).

Because 80% of the body is water and <1% is DNA, most interactions between ionizing radiation and body cells are _________.

Indirect

____ is the primary target for cell damage from ionizing radiation.

DNA

Single-Side Rail Break

Repairable

Double-Side Rail Break

May repair with difficulty or may result in cell death.

Cross-Linking

Faulty repair of breakage

Rung Breakage

Irreparable damage or cell death

Base Damage, Point Mutations

Transfer of incorrect genetic code to one of the two daughter cells, creating an abnormal gene of genetic mutation.

What are the major effects of DNA irradiation that are often a result of abnormal metabolic activity? (3)

• Chromosome aberration

• Cell death

• Malignant disease

Human cells cannot recover from radiation damage after there is ________________.

Interphase death

_____________________________ proposed that certain cellular qualities made tissues more or less radiosensitive.

The Law of Berdonie and Tribondeau

Which 3 types of cells are considered particularly radiosensitive, according to the Law of Bergonie and Tribondeau?

1. Stem (undifferentiated, or precursor) cells

2. Young, immature tissues

3. Highly mitotic cells (embryo/fetus - especially in 1st trimester)

Which types of cells are considered to be radioinsensitive?

• Brain cells

• Muscle cells

• Nerve cells

Lymphocytes (WBC)

Most radiosensitive cell. Found in bone marrow; if they suffer radiation damage, body loses ability to fight infection/disease.

Epithelial Tissue

Lines respiratory system and intestines regenerate often through mitosis.

Genetic Cells of the Gonads

Exposure to ionizing radiation can cause temporary infertility, permanent sterility, or mutations in offspring.

Muscle (myocytes) and nerve cells (neurons) are _____ sensitive to radiation.

Less

For both males and females, temporary sterilization (infertility) occurs at ________, and permanent sterilization occurs at ____________.

• 2 Gyt

• 5-6 Gyt

Factors that determine tissue response to radiation: (6)

1. Fractionation and Protraction

2. Oxygen

3. Temperature

4. Age

5. LET

6. RBE

Small doses delivered over a long period of time produce a ________________.

Lesser effect

The greater the oxygen content of tissues, the _________ is their radiosensitivity.

Greater

Tissues are more radiosensitive at ___________ temperatures.

Higher

Fetal tissue is _______ radiosensitive. As the individual ages, tissue sensitivity ___________. Radiosensitivity __________ again in old age, but only slightly.

• Most

• Decreases

• Increases

As the LET of radiation increases, the radiation’s ability to produce biologic damage _____________.

Increases

As RBE of radiation increases, the radiation’s ability to produce biologic damage ______________.

Increases

Hypoxic tumors are ______________ to treat with radiation therapy because they are ______________.

• Harder

• Less radiosensitive

The loss or change of a nitrogenous base of DNA due to radiation may result in:

• Transfer of incorrect genetic code

• Point mutations

• Base damage

• All of the above

All of the above

Which of the following groups of cells is least radiosensitive?

• Lymphocytes

• Myocytes

• Undifferentiated cells

• Spermatogonia

Myocytes