1.
An atom that has lost or gained one or more electrons is called a(n) ________. If an atom loses an electron it takes
on a(n) ________ charge. If it gains an electron it takes on a(n) ________ charge. Atoms with opposite charges
attract one another, forming ________ bonds.
ion; positive; negative; ionic
2.
In addition to protons, all atoms except hydrogen have ________ in their nuclei. Atoms of the same element that
differ in the number of neutrons in their nuclei are called ________ of one another. Some of these atoms
spontaneously break apart, releasing ________ and forming different atoms in the process. Such atoms are described
as ________.
neutrons; isotopes; energy; radioactive
3.
An atom with an outermost electron shell that is either completely full or completely empty is described as
________. Atoms with partially full outer electron shells are ________ and may gain, lose, or share electrons,
forming ________.
inert; reactive, chemical bonds
4.
Water is described as ________ because each water molecule has partial negative and positive charges. This property of
water allows water molecules to form ________ bonds with one another. The bonds between water molecules give
water a high ________ and result in surface tension.
polar; hydrogen; cohesion
5.
Large biological molecules are often formed from a series of similar smaller molecules that are linked together.
The chemical reaction that creates bonds between the smaller subunits by removing water is called ________.
The reverse reaction that breaks down these molecules by adding water is called ________. Starch and cellulose are
both formed from subunit molecules of ________, and proteins are formed from ________.
dehydration synthesis; hydrolysis; glucose, amino acids
6.
The four general classes of biological molecules are: ________, ________, ________, ________.
After each molecule, identify the general class to which it belongs:
cellulose: ________; steroid: ________; enzyme: ________; fat: ________;
disaccharide: ________; DNA: ________; glycogen: ________.
carbohydrates, lipids, proteins, nucleic acids; carbohydrate; lipid; protein; lipid; carbohydrate; nucleic acid;
carbohydrate
Review Questions
1.
Distinguish atoms from molecules; elements from compounds; and protons, neutrons, and electrons from each other.
An atom is the smallest particle of an element that still retains the properties of that element. A molecule consists of
two or more atoms chemically bonded together. Protons are positively charged subatomic particles found in the
atomic nucleus. Neutrons are uncharged subatomic particles found in the atomic nucleus. Electrons are negatively
charged subatomic particles found in electron shells around the atomic nucleus.
2.
Compare and contrast covalent bonds, ionic bonds, and hydrogen bonds.
Covalent bonds are formed by sharing electrons between two atoms. Ionic bonds result when oppositely charged ions
attract one another. The charges on the atoms result from the transfer of one or more electrons from one atom to
another to fill or empty the outer electron shell.
3.
Describe how water dissolves a salt.
The polar water molecules are attracted to the charged ions. The water molecules surround and insulate the ions
from one another, allowing the ions to separate.
4.
Define acid, base, and buffer. How do buffers reduce changes in pH when hydrogen ions or hydroxide ions are added
to a solution? Why is this phenomenon important in organisms?
An acid is a substance that releases hydrogen ions when dissolved in water. A base is a substance that combines with hydrogen
ions in water. A buffer is a compound that tends to maintain a solution at a constant pH by accepting or releasing hydrogen ions
in response to small changes in hydrogen ion concentration. Small changes in pH from normal levels found in the body can
interfere with the structure and proper functioning of biological molecules.
5.
Which elements are common components of biological molecules?
The three most abundant atoms are carbon (C), hydrogen (H), and oxygen (O); nitrogen (N) is also relatively
common (found in all amino acids and nucleic acids), and phosphorus (P) is present in nucleic acids and ATP.
6.
List the four principal types of biological molecules, and give an example of each.
Carbohydrates—glucose, sucrose, starch, glycogen, cellulose, chitin
Lipids—oils, fats, waxes, cholesterol
Proteins—keratin, silk, hemoglobin
Nucleic acids—DNA, RNA
7.
What roles do nucleotides play in organisms?
Nucleotides are subunit monomers in DNA and RNA; ATP serves as a short-term energy storage molecule; cyclic
AMP is an intracellular messenger.
8.
Distinguish among the following: monosaccharide, disaccharide, and polysaccharide. Give two examples of each and
their functions.
A monosaccharide is a single sugar molecule; glucose and ribose are examples. Monosaccharides provide energy
and serve as a building block for polysaccharides. A disaccharide is two monosaccharides bonded together; sucrose
and lactose are examples. Disaccharides are used for short-term energy storage. A polysaccharide is a long chain of
bonded monosaccharides; cellulose and glycogen are examples. Polysaccharides are used for long-term energy
storage, and many are structural components of cells.
9.
Describe the manufacture of a protein from amino acids.
Proteins are produced by dehydration synthesis of amino acids to form polypeptides bonded together by peptide
bonds.