MICR 3033 Exam 1 Questions and
Answers
Describe a hydrogen bond. - Answer-positively charged hydrogen is attracted to negatively charged
atoms, intermolecular forces hold these bonds together
A carbon atom contains six protons and six neutrons. What are its atomic number, atomic weight, and
how many electrons does it have? How many additional electrons must it add to fill its outermost shell?
- Answer-atomic number: 6
atomic weight: 12
electrons: 6
additional electrons: 4
How is an ionic bond formed? - Answer-One atom completely loses an electron while the other
completely gains that electron creating two charged molecules
What are the differences between an ionic and covalent bond? - Answer-Ionic bond: donates electrons,
creates charged molecules, very polar
Covalent: shares electrons, equally distributed charges, not very polar
, Why are polar covalent bonds and the resulting permanent dipoles so important in biology? - Answer-
Stabilize protein. Hold molecules in position during chemical reactions. Allows for the formation of the
phospholipid bilayer
Why are substances such as sugars soluble in water and others such as lipids not? - Answer-Sugars have
hydrophilic exteriors which lipids have hydrophobic exteriors. Polar substances are soluble in water
because they charged and integrate the lattice by attracting hydrogen bonds from water molecules.
Nonpolar substances, such as lipids, are not soluble in water because they repel hydrogen bonds and
disrupt the water lattice structure.
Why does an acid donate protons when in water? - Answer-Water contains an electronegative atom
(Oxygen). This atom is polar covalently bonded to two hydrogens, making it a partial negative charge.
The acid will donate a proton to the Oxygen on the water molecule.
If non-covalent interactions are so weak in a water environment , how can they possibly be important
for holding molecules together in cells? - Answer-While these bonds may be weak, there are so many of
them that exist at one time that together, they form a very strong bond.
How glucose, mannose, and galactose differ from each other? - Answer-they are different because of
different placement of hydroxyl (-OH) groups on the molecules
they are isomers: they share the same structural formula but are stereochemically different , have
different biochemical properties
Describe the formation (condensation) and disruption (hydrolysis) of a glycoside bond - Answer-A
glycoside bond occurs with the condensation of two hydroxyl groups (one from each sugar), releasing a
water molecule.
A glycosidic bond is formed by a condensation reaction when an -OH group on one sugar is bonded on
an -OH group on another while the molecule of water is expelled as the bond. The bonds created can be
broken by the reverse process (hydrolysis) in which a mol of water is consumed.
Answers
Describe a hydrogen bond. - Answer-positively charged hydrogen is attracted to negatively charged
atoms, intermolecular forces hold these bonds together
A carbon atom contains six protons and six neutrons. What are its atomic number, atomic weight, and
how many electrons does it have? How many additional electrons must it add to fill its outermost shell?
- Answer-atomic number: 6
atomic weight: 12
electrons: 6
additional electrons: 4
How is an ionic bond formed? - Answer-One atom completely loses an electron while the other
completely gains that electron creating two charged molecules
What are the differences between an ionic and covalent bond? - Answer-Ionic bond: donates electrons,
creates charged molecules, very polar
Covalent: shares electrons, equally distributed charges, not very polar
, Why are polar covalent bonds and the resulting permanent dipoles so important in biology? - Answer-
Stabilize protein. Hold molecules in position during chemical reactions. Allows for the formation of the
phospholipid bilayer
Why are substances such as sugars soluble in water and others such as lipids not? - Answer-Sugars have
hydrophilic exteriors which lipids have hydrophobic exteriors. Polar substances are soluble in water
because they charged and integrate the lattice by attracting hydrogen bonds from water molecules.
Nonpolar substances, such as lipids, are not soluble in water because they repel hydrogen bonds and
disrupt the water lattice structure.
Why does an acid donate protons when in water? - Answer-Water contains an electronegative atom
(Oxygen). This atom is polar covalently bonded to two hydrogens, making it a partial negative charge.
The acid will donate a proton to the Oxygen on the water molecule.
If non-covalent interactions are so weak in a water environment , how can they possibly be important
for holding molecules together in cells? - Answer-While these bonds may be weak, there are so many of
them that exist at one time that together, they form a very strong bond.
How glucose, mannose, and galactose differ from each other? - Answer-they are different because of
different placement of hydroxyl (-OH) groups on the molecules
they are isomers: they share the same structural formula but are stereochemically different , have
different biochemical properties
Describe the formation (condensation) and disruption (hydrolysis) of a glycoside bond - Answer-A
glycoside bond occurs with the condensation of two hydroxyl groups (one from each sugar), releasing a
water molecule.
A glycosidic bond is formed by a condensation reaction when an -OH group on one sugar is bonded on
an -OH group on another while the molecule of water is expelled as the bond. The bonds created can be
broken by the reverse process (hydrolysis) in which a mol of water is consumed.
