Unit 2 chapter 31 Human Biology: Cell Theory, Molecules, and Radiation Effects

What harmful effects can sufficiently intense x-rays cause?

Skin burns, cataracts, cancer, leukemia, and other harmful effects.

What is uncertain about exposure to diagnostic levels of x-radiation?

The degree of effect, if any, after exposure.

When are x-rays considered reasonably safe?

When ALARA is used.

What does ALARA stand for?

As Low As Reasonably Achievable.

At what level do human radiation effects begin?

At the atomic level with transfer of energy.

How does radiation energy transfer progress in the body?

From atoms through molecules to cells and beyond.

Can radiation damage be repaired?

At nearly every stage in the sequence, it is possible to repair radiation damage and recover.

What are deterministic radiation effects?

Effects that occur above a threshold and whose severity increases with dose.

What are examples of deterministic effects?

Acute Radiation Syndrome, local tissue damage, hematologic depression, and cytogenetic changes.

What are stochastic radiation effects?

Effects whose probability increases with dose, but whose severity does not.

What are examples of stochastic effects?

Leukemia, malignant diseases (cancer), life-span shortening, and genetic damage.

What are possible effects of fetal irradiation?

Prenatal death, neonatal death, congenital malformation, childhood malignancy, and diminished growth and development.

Where has most information about human radiation effects come from?

Exposures to very large radiation doses rather than diagnostic radiology.

How are high-dose radiation data used when considering low diagnostic doses?

The data are extrapolated and assumptions are made about low doses.

What approach does diagnostic radiology take toward radiation exposure?

A very conservative approach.

What is the atomic composition of the human body listed in the notes?

Approximately 60% hydrogen, 25.7% oxygen, 0.2% calcium, and other elements.

What does cell theory state?

In all plants and animals, cells are the basic functional units.

What are the five main molecules in the human body?

Water, proteins, lipids, carbohydrates, and nucleic acids.

What is a molecule?

A group of atoms bonded together representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction.

What is a macromolecule?

A very large molecule containing hundreds of thousands of atoms.

What is water composed of?

Two hydrogen atoms and one oxygen atom.

Approximately what percentage of body composition is water?

80%.

How is water related to radiation effects?

Water contributes to radiation effects, including indirect effects.

Approximately what percentage of body composition is protein?

15%.

What are proteins made of?

Long chains of amino acids connected by peptide bonds.

What determines the function of a protein?

The sequence of amino acids.

What general role do proteins have in the body?

They provide structure and support.

What do enzymes do?

Allow biochemical reactions.

What do hormones do?

Provide regulatory control of growth and development.

What do antibodies do?

Serve as primary defense mechanisms against infection and disease.

Where are lipids found?

In all tissues of the body.

What are major functions of lipids?

They are components of cell membranes, provide thermal insulation, and provide long-term energy storage that is difficult to extract.

What is the main function of carbohydrates?

They provide fuel for cell metabolism.

What are carbohydrates also called?

Saccharides.

What are the three types of saccharides listed?

Monosaccharides, disaccharides, and polysaccharides.

What structural role do carbohydrates have?

They contribute to the shape and stability of cells.

What are nucleic acids?

Very large, complex macromolecules.

What does DNA stand for?

Deoxyribonucleic acid.

Why is DNA especially important in radiation biology?

DNA is a radiation-sensitive target molecule.

Where is DNA primarily located?

In the nucleus.

What functions does DNA perform?

Command and control of the cell and heredity of the cell or whole organism.

What does RNA stand for?

Ribonucleic acid.

Where is RNA primarily located?

Primarily in the cytoplasm, with some in the nucleus.

What types of RNA are listed in the notes?

mRNA and tRNA.

What is RNA used for?

Protein synthesis.

What forms the sides of the DNA ladder?

Alternating segments of deoxyribose sugar and phosphate.

What forms the rungs of the DNA ladder?

Nitrogenous bases.

What are the purine bases?

Adenine and guanine.

What are the pyrimidine bases in DNA?

Thymine and cytosine.

What shape does DNA form?

Two long ladders form a double helix.

What are the DNA base-pair sequences?

Adenine pairs with thymine (A-T), and guanine pairs with cytosine (G-C).

How does RNA structure differ from DNA?

RNA is similar but has a single helix.

What base does RNA use instead of thymine?

Uracil.

What are the two major components of the human cell?

The nucleus and cytoplasm.

What does the nucleus house?

DNA.

Where is the nucleolus attached?

To the nuclear membrane.

What does the nucleolus contain?

Most of the RNA.

What makes up the bulk of the cell?

The cytoplasm.

Where is the endoplasmic reticulum (ER) attached?

To the nuclear membrane.

What is the function of the endoplasmic reticulum?

It forms channels that allow the nucleus to communicate with the cytoplasm.

What is the function of mitochondria?

They digest macromolecules to produce energy through catabolism.

What is the function of ribosomes?

They are the site of protein synthesis.

Where are ribosomes located?

Scattered throughout the cytoplasm and endoplasmic reticulum.

What sequence is essential for normal protein synthesis?

DNA to mRNA to ribosome to tRNA to amino acids.

What can happen if any phase of protein synthesis is interfered with?

Damage can occur.

What is the function of lysosomes?

They contain enzymes for digesting cellular fragments or the entire cell.

What is the cell membrane?

A lipid-protein barrier.

What does the cell membrane selectively allow?

Small molecules and water to enter and exit.

What other function does the cell membrane provide?

Structure and form for the cell.

What is cell proliferation?

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

What can disruption at a target molecule do to cell proliferation?

It can disrupt cell proliferation.

How much radiation is required to create measurable biologic disruption?

Many Gy.

What are the two main types of cells?

Genetic cells and somatic cells.

What are examples of genetic cells?

Oogonium and spermatogonia.

How do genetic cells divide?

By meiosis, which is reductional cell division.

How is meiosis related to mitosis?

It is like mitosis except there is one extra division without replication.

How many chromosomes does each cell produced by meiosis contain?

23 chromosomes.

What are somatic cells?

All body cells except genetic cells.

How do somatic cells divide?

By mitosis.

What is interphase?

The period of growth between cell divisions.

What occurs during G1?

It is the pre-DNA synthesis phase.

What occurs during the S phase?

DNA is replicated.

What occurs during G2?

It is the post-DNA gap.

What mnemonic identifies the subphases of mitosis?

PMAT: Prophase, Metaphase, Anaphase, Telophase.

What happens during prophase?

The nucleus swells and DNA becomes prominent and takes form.

What happens during metaphase?

Chromosomes appear and line up at the equator.

At what phase can cell division be stopped?

Metaphase.

What happens during anaphase?

Chromosomes split at the centromere.

What happens during telophase?

DNA unravels and nuclear membranes form.

How many chromosomes does each resulting somatic cell have after mitosis?

46 chromosomes, or 23 pairs.

Which cells undergo mitosis?

Somatic cells.

Which cells undergo meiosis?

Germ/genetic cells only.

What important difference occurs before the second meiotic division?

There is no additional DNA replication.

What is the general chromosome outcome of meiosis?

Cells go from the diploid condition to haploid cells containing 23 chromosomes.

What is a tissue?

A collection of cells.

How are cells identified in relation to radiosensitivity?

By their rate of division, or proliferation.

How does proliferation affect radiosensitivity?

The rate of cell division affects radiosensitivity.

What are undifferentiated, precursor, or stem cells?

Immature cells.

Are immature or mature cells more radiosensitive?

Immature cells are more sensitive to radiation than mature cells.

What is an organ?

A collection of tissues that performs a specific function as a group.