AP BIOLOGY EXAM REVIEW UNIT 1
QUESTIONS WITH CORRECT ANSWERS
How does hydrogen bonding allow for expansion upon cooling in water? - Answer-
Water is one of the few substances that are less dense as a solid than as a liquid,
meaning that ice floats on water. Instead of contracting and becoming denser as it
solidifies, water expands; as water begins to freeze (as the temperature falls from 4°C
to 0°C), more and more if it's molecules are moving too slowly to break hydrogen bonds
and become locked into a crystalline lattice (each water no like is hydrogen-bonded to
four partners).
Why is water considered a polar molecule? - Answer-The unequal sharing of electrons
and water's V-like shape make it a polar molecule, since it's overall charge is unevenly
distributed: the oxygen region of the molecule has a partial negative charge and each
hydrogen has a partial positive charge).
What is an aqueous solution? Why is water considered the universal solvent? - Answer-
An aqueous solution is one in which the solute is dissolved in water; water is the
solvent. Water is a very versatile solvent due to the polarity of the molecule. Water is
capable of dissolving ionic compounds such as salt (by surrounding individual ions with
molecules of opposing charges to separate and shield them from one another) and
polar molecules like sugars (by surrounding each of the solute molecules and form
hydrogen bonds with them). Such (biological) molecules include blood, plant sap, and
cellular liquid. Basically, it considered a universal solvent because almost anything
dissolves in it, and because it dissolves more substances than any other solvent.
What is an organic compound? - Answer-Any compounding containing the element
carbon (C), generally containing hydrogen (H) atoms as well.
Why is carbon so special compared to other elements? - Answer-Carbon is unparalleled
in its ability to form molecules that are large, complex, and varied, as its atoms have
four valence electrons (6 electrons total—2 in the first shell and 4 in the second shell)
and can hold up to 8 electrons and form up to quadruple bonds to form a lot of different
structures.
What are hydrocarbons and where can they be found? - Answer-Hydrocarbons are
organic molecules consisting of only carbon and hydrogen. They are a major
component of petroleum (they can undergo reactions that release a relatively large
amount of energy) and they are a major component in fats (hydrocarbon tails).
What are isomers? What are the three types of isomers and what are their
characteristics? - Answer-Isomers are compounds that have the same numbers of
atoms of the same elements but different structures, and hence different properties.
, 1. Structural Isomers differ in the covalent arrangements of atoms or in the location of
double bonds—the number of isomers increases tremendously as skeletal size
increases.
2. Cis-trans Isomers different in spatial arrangements due to inflexibility of double bonds
(they don't rotate like singles)—cis is in the same side while trans is on the opposite.
3. Enantiomers differ in shape due to the presence of an asymmetric carbon (one that is
attached to four different atoms or groups of atoms). They are, in a way, left-handed
and right-handed versions of the molecule.
What is a functional group? What are the seven major functional groups? - Answer-The
chemical groups that affect molecular function by being directly involved in chemical
reactions are known as functional groups.
1. Hydroxyl (—OH)
2. Carbonyl (>C=O)
3. Carboxyl (—COOH)
4. Amino (—NH2)
5. Sulfhydryl (—SH)
6. Phosphate (—OP(O3)^2-)
7. Methyl (—CH3)
All but the sulfhydryl group are hydrophilic, and all but the methyl group can act as
functional groups.
What is a hydrogen bond? - Answer-One of the weak chemical bonds that are central to
the chemistry of life; a hydrogen bond is characterized by the non-covalent attraction
between a hydrogen and an electronegative atom. When a hydrogen atom is covalently
bonded to an electronegative atom, the hydrogen atom has a partial positive charge that
allows it to be attracted to a different electronegative atom nearby. Typically, it is
attracted to nitrogen or oxygen.
Where are hydrogen bonds found in water? - Answer-Hydrogen bonds are located in
between different water molecules, connecting the partial positive charge of one of the
hydrogen atoms from one water molecule to the partial negative charge of the oxygen
molecule of another water molecule.
Where are hydrogen bounds found in DNA? How many hydrogen bonds are found
between each complementary base pairing? - Answer-In DNA, hydrogen bonds exist
between the opposing bases of complementary base pairs. This means that adenine (A)
in one strand opposes thymine (T) in the other strand, and guanine (G) opposes
cytosine (C). The A-T pair forms two hydrogen bonds, while the C-G pair forms three.
What is the structure of an amino acid? - Answer-All amino acids share a common
structure; the general formula for an amino acid contains an amino group (NH2), a
carboxyl group (COOH), a variable R group (side chain), and a hydrogen atom all
centered around an alpha carbon.
QUESTIONS WITH CORRECT ANSWERS
How does hydrogen bonding allow for expansion upon cooling in water? - Answer-
Water is one of the few substances that are less dense as a solid than as a liquid,
meaning that ice floats on water. Instead of contracting and becoming denser as it
solidifies, water expands; as water begins to freeze (as the temperature falls from 4°C
to 0°C), more and more if it's molecules are moving too slowly to break hydrogen bonds
and become locked into a crystalline lattice (each water no like is hydrogen-bonded to
four partners).
Why is water considered a polar molecule? - Answer-The unequal sharing of electrons
and water's V-like shape make it a polar molecule, since it's overall charge is unevenly
distributed: the oxygen region of the molecule has a partial negative charge and each
hydrogen has a partial positive charge).
What is an aqueous solution? Why is water considered the universal solvent? - Answer-
An aqueous solution is one in which the solute is dissolved in water; water is the
solvent. Water is a very versatile solvent due to the polarity of the molecule. Water is
capable of dissolving ionic compounds such as salt (by surrounding individual ions with
molecules of opposing charges to separate and shield them from one another) and
polar molecules like sugars (by surrounding each of the solute molecules and form
hydrogen bonds with them). Such (biological) molecules include blood, plant sap, and
cellular liquid. Basically, it considered a universal solvent because almost anything
dissolves in it, and because it dissolves more substances than any other solvent.
What is an organic compound? - Answer-Any compounding containing the element
carbon (C), generally containing hydrogen (H) atoms as well.
Why is carbon so special compared to other elements? - Answer-Carbon is unparalleled
in its ability to form molecules that are large, complex, and varied, as its atoms have
four valence electrons (6 electrons total—2 in the first shell and 4 in the second shell)
and can hold up to 8 electrons and form up to quadruple bonds to form a lot of different
structures.
What are hydrocarbons and where can they be found? - Answer-Hydrocarbons are
organic molecules consisting of only carbon and hydrogen. They are a major
component of petroleum (they can undergo reactions that release a relatively large
amount of energy) and they are a major component in fats (hydrocarbon tails).
What are isomers? What are the three types of isomers and what are their
characteristics? - Answer-Isomers are compounds that have the same numbers of
atoms of the same elements but different structures, and hence different properties.
, 1. Structural Isomers differ in the covalent arrangements of atoms or in the location of
double bonds—the number of isomers increases tremendously as skeletal size
increases.
2. Cis-trans Isomers different in spatial arrangements due to inflexibility of double bonds
(they don't rotate like singles)—cis is in the same side while trans is on the opposite.
3. Enantiomers differ in shape due to the presence of an asymmetric carbon (one that is
attached to four different atoms or groups of atoms). They are, in a way, left-handed
and right-handed versions of the molecule.
What is a functional group? What are the seven major functional groups? - Answer-The
chemical groups that affect molecular function by being directly involved in chemical
reactions are known as functional groups.
1. Hydroxyl (—OH)
2. Carbonyl (>C=O)
3. Carboxyl (—COOH)
4. Amino (—NH2)
5. Sulfhydryl (—SH)
6. Phosphate (—OP(O3)^2-)
7. Methyl (—CH3)
All but the sulfhydryl group are hydrophilic, and all but the methyl group can act as
functional groups.
What is a hydrogen bond? - Answer-One of the weak chemical bonds that are central to
the chemistry of life; a hydrogen bond is characterized by the non-covalent attraction
between a hydrogen and an electronegative atom. When a hydrogen atom is covalently
bonded to an electronegative atom, the hydrogen atom has a partial positive charge that
allows it to be attracted to a different electronegative atom nearby. Typically, it is
attracted to nitrogen or oxygen.
Where are hydrogen bonds found in water? - Answer-Hydrogen bonds are located in
between different water molecules, connecting the partial positive charge of one of the
hydrogen atoms from one water molecule to the partial negative charge of the oxygen
molecule of another water molecule.
Where are hydrogen bounds found in DNA? How many hydrogen bonds are found
between each complementary base pairing? - Answer-In DNA, hydrogen bonds exist
between the opposing bases of complementary base pairs. This means that adenine (A)
in one strand opposes thymine (T) in the other strand, and guanine (G) opposes
cytosine (C). The A-T pair forms two hydrogen bonds, while the C-G pair forms three.
What is the structure of an amino acid? - Answer-All amino acids share a common
structure; the general formula for an amino acid contains an amino group (NH2), a
carboxyl group (COOH), a variable R group (side chain), and a hydrogen atom all
centered around an alpha carbon.
