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Flashcards in The Chemistry of Life Deck (36)
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What is an element?

The simplest form of matter to have unique chemical properties.


What is the atomic number?

Each element has an atomic number which identifies the number of protons in its nucleus.


How many naturally occurring elements are there on earth?

91 naturally occurring elements are on Earth. 24 play a pivotal, normal physiological role in the human body


What are the six elements that account for 98.5% of the body's weight ?

Oxygen, nitrogen, hydrogen, carbon, calcium and phosphorus


What are the six elements that account for 0.8% of the body weight ?

Sulfur, potassium, sodium, chlorine, magnesium, iron


What are the trace elements that together account for 0.7% of the body weight, each no more than 0.02%?

Chromium, Cobalt, Copper, Flourine, Iodine, Manganese, Molybdenum, selenium, silicon, Tin, Vanadium, Zinc


What can other elements without natural physiological roles do to the body?

They can contaminate the body and severely disrupt its function, as in heavy metal poisoning with lead or mercury.


Are some elements minerals?

Yes- some elements are classified as minerals - these are inorganic elements that are extracted from the soil by plants and passed up the food chain to humans and other organisms. Minerals function in body structure, enabling the function of enzymes and other organic molecules, Almost 75% of this is Calcium and Phosphorus- other minerals are Cl, Mg, K, Na, and S


What is the atomic mass of an element?

It is approximately equal to its total number of protons and neutrons. Electrons have very low mass - it takes 1836 electrons to equal the mass of one proton, so for most purposes we can disregard their mass.


Discuss the significance of electrons in the atomic structure.

Electrons are equal to the number of protons in a neutrally charged atom and swarm about the nucleus in regions called electron shells (energy levels) The more energy an electron has, the farther away from the nucleus its orbit lies. Electrons, specifically the valence electrons, determine the chemical properties of an atom, thereby governing what molecules can exist and what chemical reactions can occur.


What are isotopes ?

Not every atom of an element is identical; what is different may be the number of neutrons.

Isotopes are variations of an element in which there are a different number of neutrons and hence a different mass number. Hydrogen has three isotopes for example - respectively containing 0, 1, and 2 neutrons. Over 99% of carbon atoms have an atomic mass of 12 (6 protons and 6 neutrons) but a small percentage of carbon atoms have seven neutrons or 8 neutrons. A sample of carbon can contain different isotopes of that element- different atoms may have the same of different number of neutrons.


Do all isotopes of a given element behave the same chemically? What about physically ?

Yes. An isotope of hydrogen for example called Deuterium (containing one neutron) reacts with oxygen the same way hydrogen (containing 0 neutrons does) Physically, not all behave the same.


What is a radioisotope?

An unstable isotope that decay(break down) into more stable isotopes by giving off radiation. The process of decay is called radioactivity. There are stable isotopes and there are unstable isotopes. Every element has at least one radioisotope- oxygen has three stable isotopes and five radioisotopes.


What are some harmless forms of radiation? What is ionizing radiation?

Light and radio waves have low energy and are harmless. Ionizing radiation causes electrons to be ejected from the atom and converts atoms into ions. Ionizing radiation can be very dangerous to the body as it can destroy molecules and produce dangerous free radicals and ions in human tissues. Examples of ionizing radiation include UV rays, X-rays and three kinds of radiation produced by nuclear decay" alpha particles, beta particles and gamma rays.


What is the physical half life of a radioisotope?

The time required for 50% of the radioisotope's atoms to decay ti a more stable state.


What is the biological half life of a radioisotope?

The time it takes 50& of a radioisotope's atoms to disappear from the body. Some of it is lost by radioactive decay and even more of it by excretion from the body.


What is an ion?

Charged particles with an unequal number of protons and electrons. Electronshave either been added tor lost. An ion can consist of a single atom with + or - charge or be as large as a protein with many charges on it.


The charge of an ion is also called its_______

Valence. Some elements have two or more ionized forms or different charges such as Fe2+ and Fe3+.




In the body, what do ions with opposite charges tend to do?

Ions with opposite charges are attracted to each other and tend to follow each other through the body. Thus when Na+ is excreted in the urine, Cl- tends to follow it.

The attraction of cations and anions to each other is important in maintaining the excitability of muscle and nerve cells.



What are electrolytes ?

Electrolytes are substances that ionize (AKA become ions) in water and form solutions capable of conducting electricity.


Acids, bases or salts are electrolytes.

Electrolytes are important for their chemical reactivity (as when calcium phosphate becomes incorporated into bone), osmotic effects (influence on water content and distribution in the body) and electrical effects (which are essential to nerve and muscle function)

Electrolyte balance is one ofthe most important considerations in patient care.


What are free radicals? Why are they harmful to the body

Chemical particles with an odd number of electrons. These can be produced by normal metabolic reactions of the body, by radiation and by chemicals.

An example is a molecule of oxygen, O2.

If an additional electron is added it becomes a free radical called the superoxide anion, 

They combine quickly with molecules such as fats, proteins and DNA converting them into free radicals and triggering chain reactions that destroy more molecules. Free radicals can cause some forms of cancer and myocardial infection, the death of heart tissue.


What are antioxidants?

Antioxidants are chemicals that neutralize free radicals.



What are molecules?

Molecules are chemical particles composed of two or more atoms united by a chemical bond. Atoms may be identical (belonging to the same element) or different. (other elements atoms are also present)


What are compounds?

Compounds are molecules composed or two or more elements.





What holds a molecule together?

Molecules are held together and attracted to one another by forces called chemical bonds.


What is an ionic bond?

The attraction of a cation to an anion. Sodium (Na+) and Chloride (Cl-) are attracted to each other and form the compound sodium chloride, NaCl.


Ionic bonds are weak and easily dissociate (break up) in the presence of something more attractive, such as water.


Covalent bonds- what are they ?

These form by the sharing of electrons between atoms. Two hydrogen atoms share valence electrons to form a hydrogen molecule, H2.




What is the strongest of all chemical bonds?

Nonpolar covalent bonds- when shared electrons spend approximately equal time around each nucleus.




What is a polar covalent bond ?

If shared electrons spend significantly more time orbiting one nucleus than they do the other, they lend their negative charge to the region where they spend the most time. When hydrogen bonds with oxygen for example, the electrons of the hydrogen atoms are more attracted to the oxygen nucleus and orbit it more than they do the hydrogen. This makes the oxygen region of the molecule slightly negative and the hydrogen regions slightly positve.


DIscuss hydrogen bonds?

Hydrogen bonds are enormously important to physiology- these are weak attractions between slighly positive hydrogen atoms in one molecule and a slightly negative oxygen or nitrogen atom in another. Water molecules are weakly attracted to each other by hydrogen bonds.

Hydrogen bonds also form between different regions of the same molecule, espcially in very large molecules such as proteins and DNA. They cause such molecules to fld or coil into precise three dimensional shapes.

Hydrogren bonds are relatively weak.