Molecular Biology Exam test quiz
and answers graded A+
What are the main implications of templated replication of DNA molecules? Why is it important to
have a semi conservative multiplication of DNA molecules?
- ANS✅✅Each strand of a DNA double helix contains a sequence of nucleotide strands, serving as
a template for the synthesis of a new complementary strand. Because each parental strand serves as
the template for one new identical strand, each of the daughter DNA double helices ends up with
one of the original strands that is completely new. This process is said to be semiconservative, since
one of the original strands is present at the end of replication.
In observing the central steps of molecular biology (see Figure above), consider the similarities
between the molecular (biological) computer (mathematical) approaches to deal with information. -
ANS✅✅DNA has a code of 4 different letters, while computers have a binary code. Both have a
basic sequence that gets interpreted to a more complex system.
What are the main differences between DNA and RNA molecules? - ANS✅✅DNA polymer chains
are made from a set of four monomers, called nucleotides (A, T, G, C), that are strung together in
different sequences to convey information that is read out, or transcribed, into a chemically related
set of polymers called RNA (A, U, G, C), which is then translated into another type of polymer called
a protein.
What are the three major groups of living organisms? - ANS✅✅Archaea, Bacteria, Eukarya
Which group has been missed in earlier biodiversity studies? Explain why? - ANS✅✅Archaea,
because traditionally all prokaryotes have been classified together in one large group. It wasn't until
recently that molecular studies revealed that there is a gulf within the class of prokaryotes. Archaea
are extremophiles. When they sequenced DNA of archaea, they have different sequences from the
other two major groups.
Define the differences between prokaryotes and eukaryotes. - ANS✅✅Prokaryotes don't have
nucleus, circular genome, binary fission. Eukaryotes have nucleus and membrane bound organelles,
more complicated.
If the isotope 32S has 16 protons and 16 neutrons, how many protons and how many neutrons will
the isotope 35S have? - ANS✅✅Isotope 35S would have 16 protons and 19 protons.
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? - ANS✅✅Atomic number = 6, Atomic weight = 12, Contains 6 electrons, Needs 4
electrons to fill outermost shell
How is an ionic bond formed? - ANS✅✅Ionic bonds are formed by atoms that gain and lose
electrons.
What are the differences between a covalent and ionic bond? - ANS✅✅Ionic bonds are formed by
atoms gaining or losing electrons to another atom, whereas covalent bonds form when electrons are
shared between two atoms.
Why are polar covalent bonds and the resulting permanent dipoles so important in biology? -
ANS✅✅They allow molecules to interact through electrical forces, when molecules with polar
covalent bonds encounter a second molecule of the same type of electrostatic attraction that
resembles an ionic bond. Causes surfaces to stick specifically to each other.
Describe a hydrogen bond. - ANS✅✅Hydrogen bonds are much weaker than covalent bonds.
Easily broken by random thermal motions. Formed by polarization.
Why are substances such as sugars soluble in water and others such as lipids not? - ANS✅✅Sugars
are soluble in water because they are polar, which attracts water, making it hydrophilic. Lipids are
nonpolar and repels water, making it hydrophobic.
What does the "p" in pH stand for? - ANS✅✅Power of hydrogen ions (negative log of the
concentration of H)
Why does an acid donate protons when in water? - ANS✅✅Hydrogen will become attracted to the
partial negative charge on the O atom of an adjacent water molecule and dissociate from the
molecule.
What does a pH=7 of pure water mean? - ANS✅✅It is neutral. Concentration of acid is same as
concentration of base.
If non-covalent interactions are so weak in a water environment, how can they possibly be
important for holding molecules together in cells? - ANS✅✅The combined effect of all the weak
bonds is rather strong. This forms a network of interlocking hydrogen bonds, which causes the
macromolecule to fold into unique 3-D shapes.
and answers graded A+
What are the main implications of templated replication of DNA molecules? Why is it important to
have a semi conservative multiplication of DNA molecules?
- ANS✅✅Each strand of a DNA double helix contains a sequence of nucleotide strands, serving as
a template for the synthesis of a new complementary strand. Because each parental strand serves as
the template for one new identical strand, each of the daughter DNA double helices ends up with
one of the original strands that is completely new. This process is said to be semiconservative, since
one of the original strands is present at the end of replication.
In observing the central steps of molecular biology (see Figure above), consider the similarities
between the molecular (biological) computer (mathematical) approaches to deal with information. -
ANS✅✅DNA has a code of 4 different letters, while computers have a binary code. Both have a
basic sequence that gets interpreted to a more complex system.
What are the main differences between DNA and RNA molecules? - ANS✅✅DNA polymer chains
are made from a set of four monomers, called nucleotides (A, T, G, C), that are strung together in
different sequences to convey information that is read out, or transcribed, into a chemically related
set of polymers called RNA (A, U, G, C), which is then translated into another type of polymer called
a protein.
What are the three major groups of living organisms? - ANS✅✅Archaea, Bacteria, Eukarya
Which group has been missed in earlier biodiversity studies? Explain why? - ANS✅✅Archaea,
because traditionally all prokaryotes have been classified together in one large group. It wasn't until
recently that molecular studies revealed that there is a gulf within the class of prokaryotes. Archaea
are extremophiles. When they sequenced DNA of archaea, they have different sequences from the
other two major groups.
Define the differences between prokaryotes and eukaryotes. - ANS✅✅Prokaryotes don't have
nucleus, circular genome, binary fission. Eukaryotes have nucleus and membrane bound organelles,
more complicated.
If the isotope 32S has 16 protons and 16 neutrons, how many protons and how many neutrons will
the isotope 35S have? - ANS✅✅Isotope 35S would have 16 protons and 19 protons.
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? - ANS✅✅Atomic number = 6, Atomic weight = 12, Contains 6 electrons, Needs 4
electrons to fill outermost shell
How is an ionic bond formed? - ANS✅✅Ionic bonds are formed by atoms that gain and lose
electrons.
What are the differences between a covalent and ionic bond? - ANS✅✅Ionic bonds are formed by
atoms gaining or losing electrons to another atom, whereas covalent bonds form when electrons are
shared between two atoms.
Why are polar covalent bonds and the resulting permanent dipoles so important in biology? -
ANS✅✅They allow molecules to interact through electrical forces, when molecules with polar
covalent bonds encounter a second molecule of the same type of electrostatic attraction that
resembles an ionic bond. Causes surfaces to stick specifically to each other.
Describe a hydrogen bond. - ANS✅✅Hydrogen bonds are much weaker than covalent bonds.
Easily broken by random thermal motions. Formed by polarization.
Why are substances such as sugars soluble in water and others such as lipids not? - ANS✅✅Sugars
are soluble in water because they are polar, which attracts water, making it hydrophilic. Lipids are
nonpolar and repels water, making it hydrophobic.
What does the "p" in pH stand for? - ANS✅✅Power of hydrogen ions (negative log of the
concentration of H)
Why does an acid donate protons when in water? - ANS✅✅Hydrogen will become attracted to the
partial negative charge on the O atom of an adjacent water molecule and dissociate from the
molecule.
What does a pH=7 of pure water mean? - ANS✅✅It is neutral. Concentration of acid is same as
concentration of base.
If non-covalent interactions are so weak in a water environment, how can they possibly be
important for holding molecules together in cells? - ANS✅✅The combined effect of all the weak
bonds is rather strong. This forms a network of interlocking hydrogen bonds, which causes the
macromolecule to fold into unique 3-D shapes.
