AP BIOLOGY EXAM REVIEW UNIT 1
What is a hydrogen bond? - Correct Answers -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? - Correct Answers -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? - Correct Answers -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? - Correct Answers -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.
What are the three options for the R group? For each R group option, describe the
polarity and justify your response. - Correct Answers -1. Hydrophilic amino acids, with a
charged or polar and uncharged R group (Glycine, Alanine, Valine, Leucine, Isoleucine,
Methionine, Phenylalanine, Tryptophan, Proline)
2. Hydrophobic amino acids, with an aliphatic or bulky and aromatic R group (Serine,
Threonine, Cysteine, Tyrosine, Asparagine, Glutamine)
3. Electrically charged side chains that are hydrophilic (Aspartic Acid, Glutamic Acid,
Lysine, Arginine, Histidine)
Water is a dipole and acts like a magnet, with the oxygen end having a negative charge
and the hydrogen end having a positive charge. These charged ends can attract other
polar molecules.
, What are three properties of water? - Correct Answers -Cohesive behavior, the ability to
moderate temperature, and expansion upon freezing.
How does hydrogen bonding allow for cohesive behavior in water? - Correct Answers -
At any given moment, many of the molecules in liquid water are linked by multiple
hydrogen bonds, which collectively hold the substance together and make water more
structured than other liquids. This allows for adhesion (the clinging of one substance to
another) and a relatively high surface tension (a measure of how difficult it is to stretch
or break the surface of a liquid).
Using the properties of water, describe how water can move up a capillary tube to move
from the roots to the leaves in a plant. - Correct Answers -Cohesion due to hydrogen
bonding contributed to the transport of water and dissolved nutrients against gravity in
plants. Water from the roots reached the leaves through a network of water-conducting
cells; as water evaporates from a leaf, hydrogen bonds cause water molecules leaving
the veins to tug on molecules farther down, and the upward pull is transmitted through
the water-conducting cells all the way to the roots.
Using the properties of water, describe how a water strider can walk on water. - Correct
Answers -The hydrogen bonds in water give it an unusually high surface tension,
making it behave as though it were coated with an invisible film. A water strider can take
advantage of water's resistance to surface breakage in order to walk across it.
How does hydrogen bonding allow for the ability to moderate temperature in water? -
Correct Answers -The ability of water to stabilize temperature steams from its relatively
high specific heat (the amount of heat that must be absorbed or released for 1g of that
substance to change its temperature by 1°C). This is because heat must be absorbed in
order to break hydrogen bonds and released in order to form them; so much heat is
needed to disrupt these molecules before water molecules can speed up.
How does hydrogen bonding allow for expansion upon cooling in water? - Correct
Answers -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? - Correct Answers -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 hydrolysis? - Correct Answers -The process by which polymers are
disassembled to monomers by essentially reversing the dehydration reaction.
Hydrolysis means water breakage, so this implies that the bond between the monomers
What is a hydrogen bond? - Correct Answers -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? - Correct Answers -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? - Correct Answers -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? - Correct Answers -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.
What are the three options for the R group? For each R group option, describe the
polarity and justify your response. - Correct Answers -1. Hydrophilic amino acids, with a
charged or polar and uncharged R group (Glycine, Alanine, Valine, Leucine, Isoleucine,
Methionine, Phenylalanine, Tryptophan, Proline)
2. Hydrophobic amino acids, with an aliphatic or bulky and aromatic R group (Serine,
Threonine, Cysteine, Tyrosine, Asparagine, Glutamine)
3. Electrically charged side chains that are hydrophilic (Aspartic Acid, Glutamic Acid,
Lysine, Arginine, Histidine)
Water is a dipole and acts like a magnet, with the oxygen end having a negative charge
and the hydrogen end having a positive charge. These charged ends can attract other
polar molecules.
, What are three properties of water? - Correct Answers -Cohesive behavior, the ability to
moderate temperature, and expansion upon freezing.
How does hydrogen bonding allow for cohesive behavior in water? - Correct Answers -
At any given moment, many of the molecules in liquid water are linked by multiple
hydrogen bonds, which collectively hold the substance together and make water more
structured than other liquids. This allows for adhesion (the clinging of one substance to
another) and a relatively high surface tension (a measure of how difficult it is to stretch
or break the surface of a liquid).
Using the properties of water, describe how water can move up a capillary tube to move
from the roots to the leaves in a plant. - Correct Answers -Cohesion due to hydrogen
bonding contributed to the transport of water and dissolved nutrients against gravity in
plants. Water from the roots reached the leaves through a network of water-conducting
cells; as water evaporates from a leaf, hydrogen bonds cause water molecules leaving
the veins to tug on molecules farther down, and the upward pull is transmitted through
the water-conducting cells all the way to the roots.
Using the properties of water, describe how a water strider can walk on water. - Correct
Answers -The hydrogen bonds in water give it an unusually high surface tension,
making it behave as though it were coated with an invisible film. A water strider can take
advantage of water's resistance to surface breakage in order to walk across it.
How does hydrogen bonding allow for the ability to moderate temperature in water? -
Correct Answers -The ability of water to stabilize temperature steams from its relatively
high specific heat (the amount of heat that must be absorbed or released for 1g of that
substance to change its temperature by 1°C). This is because heat must be absorbed in
order to break hydrogen bonds and released in order to form them; so much heat is
needed to disrupt these molecules before water molecules can speed up.
How does hydrogen bonding allow for expansion upon cooling in water? - Correct
Answers -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? - Correct Answers -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 hydrolysis? - Correct Answers -The process by which polymers are
disassembled to monomers by essentially reversing the dehydration reaction.
Hydrolysis means water breakage, so this implies that the bond between the monomers
