Fall NM: Radbio

hierarchy of biological structures

cells → tissue → organ → system → organism

on which hierarchy level causes radiation and molecular damage

cellular level causes effects

what is the cell structure we mainly focues on reguarding radiation exposure

nucleus

why do we focus on the nucleus with radiation exposure

because its holds DNA and other genetic material

besides the nucelus and cytoplasm what are the 2 sections of a cell

• nuclear envelope

• organelles

the nucleus and cytoplasm are separated by what

nuclear envelope

what does cells contain

organelles

what are the nitrogenous bases of DNA that form a nucleotide and is the “back bone”

5-carbon sugar and phosphoric acid (phosphate

what are the bases of DNA

• g → guanine/ c→ cytosine

• a → adenine/ t→ thymine

what composition of the cell is made of organic and inorganic compounds; 70-85% water

protoplasm

why is water important in cell composition

it acts as a dispersion medium, method of transportation, and temperature control

what are the inorganic compounds of the cell

• salts like NA and K+

what are Na and K+ important

because they regulate osmotic pressure in the cell membrane to maintain its integrity while also aiding in energy productions and impulse conduction

4 classes of compounds in a cell

1. protiens

2. carbohydrates

3. nucleic acids

4. lipids

amino acids are joined bey peptide bonds to form

monomers

15% of cell content

protiens

monomers join through polymerization to form polymers or

enzymes

what are protiens that act as catalysts for chemical reaction

enzymes

1% of cell content composed of carbon, hydrogen, and oxygen

• Primary source of energy in a cell

Carbohydrates

which carb is a simple sugar

monosaccharides

which carb is a simple sugar (i.e. table sugar, dextrose, sucrose, and fructose)

disaccharides

what carb is a macro molecule

polysaccharides

protplasm within the nucleus

nucleoplasm

site of all metabolic function including anabolism and catabolsim

cytoplasm

catabolism

breaking down of organic compounds to provide energy; organelles suspended in ground cytoplasm, or matrix

anabolism

building up of organic compounds

what part of the cell functions as a monitor to all intracellular and extracellular fluids and has a selectively permeable membrane that conductes electric impulses

cell membrane

double membrane system that is a irregular network of branching and connecting tubules considered to be an extension of the nuclear membrane

endoplasmic reticulum

endoplasmic reticulum that has ribosomes on the surface (found mainly in cells synthesising protiens)

granular/ rough surfaced endoplasmic reticulum

endoplasmic reticulum that have no ribosomes( found more cells synthesizing products more than protiens)

agranular endoplasmic reticulum

ribosomes “read and translate”

made of RNA and is the site of protein synthesis which mRNA carries messages from the nucleus of what type of protein to make, then assembles amino acids to make said protein

mitochondria “powerhouse”

breaks down nutrients to make energy through oxidation with its energy source beign carbs inner foldings contain cristae

lysosomes

single membraned and contain enzymes capable of breaking down protiens, DNA and some carbs through digesting or lysing the cell if released

golgi complex

usually a stacked double membrane structures and small vesicles that doesnt have a fully known function

cristae

contains specific enzymes for energy production with greater energy needs of the cell

controls the passage of some molecules

diaphragm

“rungs of the ladder” that are nitrogenous bases joined by hydrogen bonds

• PURINES

adenine and guanine

“rungs of the ladder” that are nitrogenous bases joined by hydrogen bonds

• PYRIMIDINES

thymine and cytosine

if DNA is contianed in “thread like “ structers called chromosomes what are the arms of the chromosomes divided by

centromeres

genomes contains how many genes

60,000 w/ 10^9 bases

what are the two types of cells

germ cells and somatic cells

• female cells (oocytes)

• male cells (spermatozoa)

• single chromosomes

• halpoid (n) half genetic material

Germ cells

• carry 2 of each kind of gene located on 2 different chromosomes

• homologues (paired chromosomes )

• diploid (2n) in humans 46 chrom. pairs

somatic cells

mitosis

cell division where one parent cells divides to form into 2 identical daughters

prophase

during this phase, chromosomes thicken, divide, and migrate to the center of the cell (equatorial plate)spindles form and stretch from pole to pole of the cell, attached at the ends by centrioles

metaphase

chromosomes line up at equatorial plate; centromere of each chromosome pair attached to spindle; centromere duplicates, opposing

anaphase

wo chromatids repel each other and migrate along spindle to opposite poles; at end of anaphase, each duplicated chromosome is at opposite poles

telophase

chromosomes become elongated strands, lose their thickened appearance; nuclear membrane is reconstructed around new genetic material; division of the cytoplasm also occurs

interphase

a "resting" phase of no mitotic activity; individual chromosomes are not visible; DNA synthesis is occurring, however; this phase is subdivided into 4 additional stages:

S phase of Interphase

DNA Synthesis occurs; produces identical DNA molecules; DNA unwinds and splits to serve as template for replication; net result is two DNA molecules that are exact replicas of the original

G₁ Phase of Interphase

period between telophase of mitosis, and "S" phase of DNA synthesis; "G" stands for "gap"; DNA is not replicating during this time

G₂ Phase of Interphase

Another period of no DNA replication, between "S" phase of DNA replication and first phase of mitosis (prophase

meiosis

process of division for germ cells; reduces number of chromosomes to be haploid;

cells divide twice in succession, but chromosomes are duplicated only once; same mitosis

phase names apply; all is same through end of telophase; at end of telophase, daughter cells

undergo second division, but without replication of DNA and duplication of chromosome

crossing over

exchange of genes between sister chromatids, allowing for increased

genetic variability

radiology is

the study of the action of (ionizing) radiation on living things

molecular radiobiology

the study of interaction of (ionizing) radiation and biological matter at the sub-cellular level

T or F: if someone is exposed to radiation, radation interaction in cells WILL haooen and cause dammage

False

the intial deopsition of energy occurs how rapidly

10^-17 of a sec

T or F: radiation interaction in a cell nonselective

True ionizing radiation is randomly deposited into the cell no area of the cell is “chosen” by radiation

T or F: The visible changes in the cells, tissues, and organs resulting from an interaction

with ionizing radiation are not unique

True ; they cant be distinguished from say sun burn or 3rd degree burn ( any truama(

latent period

the biologic changes in cells and tissues resulting from radiation occur only after a

period of time (can be min, days, even years…. varies heavily)

2 methods of ionizing radiation injury at the molecular level

direct action and indirect action

direct action (high LET or densely-ionizing)

occurs when any type of radiation deposits energy directly in the critical target, resulting in ionization or excitation of this target.

Indirect action

occurs when radiation interacts with a water molecule; the reactive species created by this interaction cause the biological damage. Since cell is over 80% water, this is the overall dominant interaction.

charge of alpha radiation

2+ (from photon)

charge of beta radiation

(-)

does alpha radiation have mass

yes

does beta radiation have mass

yes a very small amount

alpha radiation type

helium nucleus

gamma radiation type

nucleus

gamma radiation charge

no charge

x-ray radiation charge

no charge

what differentiates the type of radiation

where the photons come from in the cell

Low-LET radiation

sparsley ionizing due to low charge and low mass (gamma and x-ray)

High-LET radiation

large mass and/or charge makes them densely ionizing; greater probability of interacting (alpha and beta)

polonium-210 experiment

munro used a ²¹⁰Po microneedle to selectively irradiate either the cytoplasm or nucleus

• dose to the cytoplasm produced no effect

• dose to the nucleus proved to be lethal to the cell

ionization

the removal of an orbital electron from an atom or molecule

why is water the primary endpoint for indirect action

because it is so abudant in biological matter

free radical

the "species" produced by interaction between water molecule and radiation; symbolized by a dot; contain a single unpaired electron in the outer shell, a state which renders them chemically unstable. Stability is dependent upon electrons paired in spin. Free radicals have an uneven number of electrons that are also unpaired in spin, a high degree of reactivity.

indirect action result

formation of an ion pari and free radicals

the ion pair may…

• recombine to form a stable water molecule (most likely)

• may chemically react to damage cellular mlecules

T or F: with radiation damage to DNA much of the damage can be and is repaired

True (not all damage is equal biologically)

DNA radiation damage

• base damage

change or loss of a base

DNA radiation damage

• single strand breaks

break in backbone of one DNA molecule

DNA radiation damage

• double strand breaks

break in both chains of the molecule

DNA radiation damage

• Crosslinks

either within molecule or to another

radiation effects of chromosomes

• breaking of chromosome

producing fragements is overall result

radiation effects of chromosomes

• broken ends can join with other broken ends

forming new chromosomes

radiation effects of chromosomes

• changes called

abberations, lesions, or anomalies

Chromatid aberrations occur from

breaks made after DNA synthesis; only one of two daughter cells is affected

Structural Changes produces by radiation can include:

• Single break in one chromosome or chromatid

• Single break in separate chromosomes or chromatids

• Two or more breaks in the same chromosome or chromatid

• "Stickiness", or clumping, or chromosome

Restitution

broken ends rejoin with no visible damage (95% of time)

deletion

fragment lost at next mitosis

Broken ends rearrange, producing a grossly distorted chromosome;

e.g.,

dicentrics, rings, anaphase bridges

Rearrangement of broken ends without visible damage; e.g.,

translocations, inversions; mutation results

Acentric fragments and dicentric rings

Break in the arms of two different chromosomes before replication results in

four chromosome fragments, two with centromeres, and two without

centromeres, each having broken sticky ends

acentric chromatid;

If two chromatids without a centromere join

dicentric chromatid.

two chromatids with a centromere join

Ring Chromosomes

Each arm of a chromatid is broken. Two broken ends that contain the

centromere rejoin, forming a ring. An acentric fragment is also formed.

Ring can be replicated, twisted, etc. to form bizarre-looking chromosomes.

One daughter cell will have chromosome deficiency, other will have excess.

Chromosome Stickiness

Occurs from irradiation during cell division. Possibly an alteration of the

chemical composition of the chromosomes that are clumped during

anaphase, causing them to adhere to each other.