Rad Bio Chpt 6 + 7

Functions of cells (4)

1. Conduct nerve impulses

2. Muscle contraction

3. Support organs

4. Transport fluid

What does the body need to ensure efficient cell operation? (3)

1. Food - for release of energy

2. Oxygen - to break down food

3. Water - to transport inorganic substances

Protoplasm and it’s function

Chemical building material for all living things

1. Metabolism

2. Processing food and oxygen

3. Elimination of waste products

What does protoplasm consist of?

Organic and inorganic materials

The biomolecules that constitute protoplasm are formed from what four primary components?

Carbon

Hydrogen

Oxygen

Nitrogen

What are the major organic compounds and what are they formed from?

The four primary components of carbon, hydrogen, nitrogen, and oxygen COMBINED with phosphorus and sulfur

1. Proteins

2. Carbohydrates

3. Lipids

4. Nucleic acids

What are the most important inorganic substances and what do they do?

Water - regulate body temperature, transport substances

Mineral salts - produce energy, aid in conduction of nerve impulses, prevent muscle cramping

Proteins

Elementary building blocks of cells, make up about 15%

Essential for growth, new tissue, and repairing old tissue

Formed from 22 specific amino acids (NH2 + COOH)

Protein synthesis

A process where amino acids are arranged to create protein; function determined by arrangement and type of protein

(Can also be arranged into chromosomes and genes)

What are the three most common types of protein and what do they do?

1. Structural - provide body with shape + form, source of heat and energy

2. Enzymatic - organic catalysts that affect chemical reactions, moderate the cells physiological activity’s

3. Repair - mend damaged molecules, effective for radiation-induced cell injury

Therapeutic ratio

In radiation therapy - Using enough radiation to kill cancerous cells while delivering a less dose to the surrounding noncancerous tissue structure

What organic compound also functions as hormones and antibodies?

Proteins

Antibodies

Protein molecules created by B lymphocytes that help with immune reactions

Carbohydrates

Simple to complex compounds that include starches and various sugars, make up 1%

Function as short-term energy for the body and provide fuel for cell metabolism

Most abundant in liver and muscle

Simple sugars

Known as monosaccharides

All contain six carbon atoms and six molecules of water

Glucose, fructose, and galactose

Glucose is the primary energy source

Disaccharides

Two units of simple sugar linked together

Sucrose and lactose

Polysaccharides

Several or many molecules of simple sugar linked together

Plant starches and animal glcogen

Lipids

Fats, fatty acids, oil, or wax that dissolve in alcohol but not water

Made up of a molecule of glycerin and three molecules of fatty acids

Structural parts of cell membrane, make up 2% but found in all body tissue

Long term storage of energy, insulate body, support and protect organs, growth and development, lubrication, assist in digestion

Nucleic acids

Complex macromolecules made of nucleotides (nitrogen organic base + five-carbon sugar molecule + phosphate molecule) makes up 1%

What are the two types of nucleic acids?

Deoxyribonucleic acid (DNA)

Ribonucleic acid (RNA)

What is DNA composed of?

Two long sugar-phosphate chains twisted together, linked by nitrogenous organic bases and hydrogen bonds at the sugar molecule of the chain

What does DNA do?

-Regulates cellular activity to direct protein synthesis

-Determines personal characteristics

-Constitutes genetic code with nitrogenous base pairs

What does mRNA do and how is it different from DNA? (messenger rna)

-Makes proteins using amino acids

-Single stranded

What does tRNA do? (transfer RNA)

-Receives genetic code from mRNA
-Combines with amino acids and attaches to ribosomes to form chainlike protein molecules
-At least 22 types
-Creates proteins necessary to provide for needs of cells

what does rRNA do? (ribosomal RNA)

Assists in linking of mRNA to ribosome

Difference between chromosomes and genes

Chromosomes
1. tiny rod-shaped, only visible in dividing cells
2. composed of DNA + protein
3. 23 pairs in somatic cells, 23 TOTAL in reproductive cells
Genes
1. segments of DNA
2. info responsible for growth and development
3. control formation of proteins

What is the human genome?

Total amount of genetic material contained within chromosomes of a human being

Water comprises how much of the body’s weight?

80 to 85%

Function of water in and outside the cell

Inside
1. Medium of chemical reactions
2. Keeps compounds dissolved
Outside
1. Transportation
2. Temp regulation
3. Lubrication
4. Protection

Function of mineral salts within cell

1. Maintain osmotic pressure

2. Necessary for cell performance, energy, and conduction

What are the components of a natural human cell?

1. Cell membrane

2. Cytoplasm

3. Organelles

4. Nucleus

Function of cell membrane

Barricade to protect other organelles

Controls passage of materials in and out of cell
Elimination of waste and refining of material

Function of endoplasmic reticulum

Allows cell communication with extracellular environment and transfer of food

Function of golgi apparatus

Unites carbohydrate molecules + combines with proteins to form glycoproteins
Transports enzymes and hormones

Function of mitochondria

Provides energy for cellular activity

Function of lysosomes

Dispose of particles
Breaks down and digests proteins, carbs, and possibly cell

Function of ribosomes

Create various proteins

Function of centrosomes

Formation of mitotic spindle during cell division

Function of nucleolus

Holds large amount of RNA

Process of mitosis

Interphase - cell growth before actual mitosis
Prophase
Metaphase
Anaphase
Telophase

Meiosis

Reduces number of chromosomes in each daughter cell to half the number of chromosomes in parent cell

Term for identical twins

Monozygotic

Term for fraternal twins

Dizygotic

Term for more than two twins

Polyzygotic

Potential harmful effects of ionizing radiation occur at what level

Cellular

What varies among the different types of radiation?

Charge, mass, and energy

Three important concepts of understanding biological damage of radiation

1. Linear energy transfer

2. Relative biologic effectiveness

3. Oxygen enhancement ratio

Linear energy transfer (LET)

-The average energy deposited per unit length as radiation passes through its path

-keV/μm

Examples of high-LET and low-LET

Low

1. gamma + x-ray

High

1. Alpha

2. Heavy nuclei

3. Charged particles

4. Low-energy neutrons

Relative Biologic Effectiveness (RBE)

How much damage other radiation produces compared to x-ray to both cause the same biologic damage (Dose in Gyt from 250 kVp / Dose in Gyt of test radiation)

Oxygen Enhancement Ratio (OER)

Ratio of the dose required to cause biologic damage of cells in any oxygen deprived environment to the dose required to cause an identical response under normal oxygenated conditions (typically 3 OER for x-ray + gamma)

Any visible radiation induced injuries always begin with damage at what level?

Molecular

Biologic damage from radiation exposure may be observed on what three levels?

Molecular - forms structurally changed molecules that impair cell function

Cellular - disturbs chemical balance and performance

Organic - entire body processes affected

Direct vs indirect interaction on cells from radiation exposure

Direct - in DNA

Indirect - in H2O

Almost always indirect, because body composition is mostly water

What is radiolysis?

Ionization of water molecules

What does radiolysis of water produce?

Ions, free radicals, chemical reactions, and damaging substances

How do free radicals cause damage to DNA?

They migrate and interact with DNA / molecules destructively

What can a double-strand break in the same DNA rung cause?

A broken chromosome containing unequal genetic material

What happens if a damaged chromosome divides?

Daughter cell may receive incorrect amounts of genetic material

What can high-energy radiation do to DNA bases?

Cause loss or alteration of nitrogenous bases

What is a covalent cross-link?

A chemical union formed by sharing one or more pairs of electrons

What can radiation-induced cross-links connect?

Different parts of molecules

What is an intrastrand cross-link?

A cross-link within the same DNA strand

What is an interstrand cross-link?

A cross-link between DNA strands

What is a single-strand DNA break?

Often reversible rupture of DNA molecule chemical band, possible severing of sugar-phosphate

What is a double-strand break in DNA?

-Further exposure that can lead to additional breaks in sugar-phosphate chain

-Possibly repairable

-More common with high LET

Mutation in DNA due to ionizing radiation

1. Incorrect genetic info transferred during cell division

2.