BIOC 3022: EXAM 1 QUESTIONS AND
VERIFIED ANSWERS
Sucrose is composed of which two monosaccharides? - answer glucose and fructose
True or False: Sucrose and sucralose are fundamentally similar to one another. - answer
True, the main difference between sucrose and sucralose is that sucralose has three
chlorine atoms in the place of hydroxides - making sucralose composed of galactose
and fructose rather than glucose and fructose
Why is it advantageous for sucralose to look very similar to sucrose? - answer Due to
their extreme likeness, sucralose can bind to the sweet taste receptor. However, it does
not look similar enough to bind sucrase because every atom has to be in the right
position and therefore it cannot be metabolized and is zero calories
What is a covalent bond? - answer A covalent bond occurs when an electron is shared
between atoms
Under physiological conditions, what is the strongest bond? - answer The strongest
bond under physiology conditions are nonpolar covalent bonds
Is the H-H bond polar or nonpolar? - answer Nonpolar
What occurs in a nonpolar covalent bond? - answer In a nonpolar covalent bond, the
atoms have identical or very similar electronegativity and therefore, the atoms are
shared equally and no atom has a charge
What occurs in a polar covalent bond? - answer In a polar covalent bond, the atoms
differ in terms of electronegativity and therefore, the electrons being shared spend
more time around the more electronegative atom, giving it a partial negative charge
while the other atom has a partial positive charge
Electronegativity differences equal to what indicate nonpolar covalent bonds? - answer
Electronegativity differences of less than 0.5 indicate nonpolar covalent bonds
What electronegativity differences indicate a polar covalent bond? - answer
Electronegativity differences greater than 0.5 and less than 1.9 indicate polar covalent
bonds
What electronegativity differences indicate substantially ionic bonds? - answer
Differences of 2 or more indicate substantially ionic bonds
True or False: There are a couple different bonds that fall between the strength of ionic
,and covalent bonds. - answer False, there is no dividing line between ionic and covalent
bonds - most bonds fall in either of these categories
Molecular polarity is due to what? - answer Molecular polarity is due to individual bond
polarities and lone-pair contributions (electrons are displaced toward the more EN
atom)
True or False: Much of the polarity present within an H2O molecule are due to the lone
pairs present on the oxygen atom - answer False, while oxygen in the water molecule
has two unshared electron pairs, these are not the sole source of water's polarity. The
polar covalent O-H bonds leaves the hydrogen molecules with a partial positive charge
Describe what occurs in an ionic bond. - answer In an ionic bond, an electron is not
shared but donated to another nucleus - these bonds occur due to the electrostatic
attractions between cations and anions.
Why, under physiological conditions, are ionic bonds not the strongest? - answer In a
physiological environment, aqueous, ions are hydrated and therefore can be easily
broken
True or False: Water molecules can solvate both cations and anions at the same time -
answer True! Water molecules can solvate both anions and cations - they just have to be
in specific orientations
From the following bonds, tell whether or not they're NPC, PC, or Ionic:
1. H-H
2. C-H
3. N-H
4. N-C
5. O-H
6. Na-Cl - answer 1. NPC
2. NPC
3. PC
4. NPC
5. PC
6. Ionic
, Describe what occurs in hydrogen bonds - answer Hydrogen bonds form due to the
weak electrostatic attractions involving a covalently bound H and two electronegative
atoms (O, N)
How many atoms are needed to make a hydrogen bond? - answer Three atoms atoms
are required to make an H-bond
Describe the common donors and the common acceptors in an H-bond - answer Most of
the H-bond donors will be OH and NH groups. Most of the H-bond acceptors will be O
and N atoms
How many atoms are required to form a covalent and ionic bond? - answer Two atoms
are required
The strongest H-bond is one that is what? - answer Straight! Hydrogen bonds are
strongest when they are straight.
Why are hydrogen bonds important in biochemistry? - answer - They are essential for
proteins to adopt their final structures
- They are essential for enzymes to bind their substrates
- They hold DNA double helix together
How many hydrogen bonds can a water molecule make? - answer A water molecule can
make four hydrogen bonds
Hydrogen bonds are responsible for the unique properties of water - give these unique
properties - answer 1. Cohesiveness/adhesiveness
2. High heat capacity
3. High heat of vaporization
4. Expansion upon freezing
5. Versatility as a solvent
- No other molecule has all these properties
VERIFIED ANSWERS
Sucrose is composed of which two monosaccharides? - answer glucose and fructose
True or False: Sucrose and sucralose are fundamentally similar to one another. - answer
True, the main difference between sucrose and sucralose is that sucralose has three
chlorine atoms in the place of hydroxides - making sucralose composed of galactose
and fructose rather than glucose and fructose
Why is it advantageous for sucralose to look very similar to sucrose? - answer Due to
their extreme likeness, sucralose can bind to the sweet taste receptor. However, it does
not look similar enough to bind sucrase because every atom has to be in the right
position and therefore it cannot be metabolized and is zero calories
What is a covalent bond? - answer A covalent bond occurs when an electron is shared
between atoms
Under physiological conditions, what is the strongest bond? - answer The strongest
bond under physiology conditions are nonpolar covalent bonds
Is the H-H bond polar or nonpolar? - answer Nonpolar
What occurs in a nonpolar covalent bond? - answer In a nonpolar covalent bond, the
atoms have identical or very similar electronegativity and therefore, the atoms are
shared equally and no atom has a charge
What occurs in a polar covalent bond? - answer In a polar covalent bond, the atoms
differ in terms of electronegativity and therefore, the electrons being shared spend
more time around the more electronegative atom, giving it a partial negative charge
while the other atom has a partial positive charge
Electronegativity differences equal to what indicate nonpolar covalent bonds? - answer
Electronegativity differences of less than 0.5 indicate nonpolar covalent bonds
What electronegativity differences indicate a polar covalent bond? - answer
Electronegativity differences greater than 0.5 and less than 1.9 indicate polar covalent
bonds
What electronegativity differences indicate substantially ionic bonds? - answer
Differences of 2 or more indicate substantially ionic bonds
True or False: There are a couple different bonds that fall between the strength of ionic
,and covalent bonds. - answer False, there is no dividing line between ionic and covalent
bonds - most bonds fall in either of these categories
Molecular polarity is due to what? - answer Molecular polarity is due to individual bond
polarities and lone-pair contributions (electrons are displaced toward the more EN
atom)
True or False: Much of the polarity present within an H2O molecule are due to the lone
pairs present on the oxygen atom - answer False, while oxygen in the water molecule
has two unshared electron pairs, these are not the sole source of water's polarity. The
polar covalent O-H bonds leaves the hydrogen molecules with a partial positive charge
Describe what occurs in an ionic bond. - answer In an ionic bond, an electron is not
shared but donated to another nucleus - these bonds occur due to the electrostatic
attractions between cations and anions.
Why, under physiological conditions, are ionic bonds not the strongest? - answer In a
physiological environment, aqueous, ions are hydrated and therefore can be easily
broken
True or False: Water molecules can solvate both cations and anions at the same time -
answer True! Water molecules can solvate both anions and cations - they just have to be
in specific orientations
From the following bonds, tell whether or not they're NPC, PC, or Ionic:
1. H-H
2. C-H
3. N-H
4. N-C
5. O-H
6. Na-Cl - answer 1. NPC
2. NPC
3. PC
4. NPC
5. PC
6. Ionic
, Describe what occurs in hydrogen bonds - answer Hydrogen bonds form due to the
weak electrostatic attractions involving a covalently bound H and two electronegative
atoms (O, N)
How many atoms are needed to make a hydrogen bond? - answer Three atoms atoms
are required to make an H-bond
Describe the common donors and the common acceptors in an H-bond - answer Most of
the H-bond donors will be OH and NH groups. Most of the H-bond acceptors will be O
and N atoms
How many atoms are required to form a covalent and ionic bond? - answer Two atoms
are required
The strongest H-bond is one that is what? - answer Straight! Hydrogen bonds are
strongest when they are straight.
Why are hydrogen bonds important in biochemistry? - answer - They are essential for
proteins to adopt their final structures
- They are essential for enzymes to bind their substrates
- They hold DNA double helix together
How many hydrogen bonds can a water molecule make? - answer A water molecule can
make four hydrogen bonds
Hydrogen bonds are responsible for the unique properties of water - give these unique
properties - answer 1. Cohesiveness/adhesiveness
2. High heat capacity
3. High heat of vaporization
4. Expansion upon freezing
5. Versatility as a solvent
- No other molecule has all these properties
