The Chemical Level of Organization Flashcards
Define an atom
An atom is the smallest stable unit of matter.
How is it possible for two samples of hydrogen to contain the same number of atoms but have different weights?
The two samples could have different weights if they contain different proportions of hydrogen’s three isotopes: hydrogen-1, with a mass of 1; hydrogen-2, with a mass of 2; and hydrogen-3, with a mass of 3.
Define chemical bond, and identify several types of chemical bonds.
A chemical bond is an attractive force acting between two atoms that may be strong enough to hold them together in a molecule or compound. The strongest attractive forces result from the gain, loss, or sharing of electrons. Examples of such chemical bonds are ionic bonds and covalent bonds.
Oxygen and neon are both gases at room temperature. Why does oxygen combine readily with other elements, but neon does not?
Atoms combine with each other such that their outer electron shells are full. Oxygen atoms do not have a full outer electron shell and so readily combine with many other elements to attain this stable arrangement. Neon does not combine with other elements because it has a full outer electron shell.
What kind of bond holds atoms in a water molecule together? What attracts water molecules to each other?
Polar covalent bonds hold together the atoms in a water molecule. Hydrogen bonds attract water molecules to each other: attraction between a slight negative charge on the oxygen atom of one water molecule and a slight positive charge on the hydrogen atom of another water molecule.
Using the rules for chemical notation, write the molecular formula for glucose, a compound composed of 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms.
The molecular formula for glucose, a compound composed of 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms, is C6H12O6.
Identify and describe three types of chemical reactions important to human physiology.
Three types of chemical reactions important to human physiology are decomposition reactions, synthesis reactions, and exchange reactions. In a decomposition reaction, a chemical reaction breaks a molecule into smaller fragments. A synthesis reaction assembles smaller molecules into larger ones. In an exchange reaction, parts of the reacting molecules are shuffled around to produce new products.
In living cells, glucose, a six-carbon molecule, is converted into two three-carbon molecules. What type of chemical reaction is this?
Because this reaction involves a large molecule being broken down into two smaller ones, it is a decomposition reaction.
If the product of a reversible reaction is continuously removed, what will be the effect on the equilibrium of the reaction?
Removing the product of a reversible reaction would keep its concentration lower than the concentrations of the reactants. As a result, the breakdown of the product into reactants would slow, producing a shift in the equilibrium toward the product.
What is an enzyme?
An enzyme is a special molecule that lowers the activation energy of a chemical reaction, which is the energy required to start the reaction.
Why are enzymes needed in our cells?
Without enzymes, most chemical reactions could proceed in the body only under conditions that cells cannot tolerate (such as high temperatures). By lowering the activation energy, enzymes make it possible for chemical reactions to proceed under conditions compatible with life.
Distinguish between inorganic compounds and organic compounds.
Inorganic compounds are substances that generally do not contain carbon and hydrogen. (If present, they do not form C—H bonds.) Organic compounds are substances that contain carbon covalently bonded with one or more other elements.
List the chemical properties of water that make life possible.
Specific chemical properties of water that make life possible include its reactivity (it participates in many chemical reactions), its high heat capacity (it absorbs and releases heat slowly), and its ability to dissolve a remarkable number of inorganic and organic substances (its strong polarity enables it to be an excellent solvent).
Why does water resist changes in temperature?
Heat is an increase in the random motion, or kinetic energy, of molecules, and temperature is a measure of heat. Liquid water resists changes in temperature because hydrogen bonds between water molecules retard molecular motion and must be broken to increase the temperature. Temperature must be quite high before individual water molecules have enough energy to break free of all surrounding hydrogen bonds and become water vapor.
Define pH, and explain how the pH scale relates to acidity and alkalinity.
pH is a measure of the concentration of hydrogen ions in solutions, such as body fluids. On the pH scale, 7 represents neutrality, values below 7 indicate acidic solutions, and values above 7 indicate alkaline (basic) solutions.
