-
Which of the following is true of carbon?
It can form polar and nonpolar bonds.
-
Consider the following
reaction at equilibrium: CO2 + H2O ↔ H2CO3.
What would be the effect of adding
additional CO2 and H20?
drive the equilibrium dynamics to the right and H2CO3 levels will increase
-
Which of the following involves an increase in
entropy?
hydrolysis
-
Which statement about spontaneous generation is
false?
- It occurs every time a new
- species evolves from a preexisting species.
-
Which reaction is most spontaneous?
a reaction that is slightly exothermic and leads to a huge increase in entropy
-
Recall the experiment on ant navigation. What parameters would have to be held constant for the test group of 75 ants in order to run a controlled experiment?
- All variables except leg
- length (and therefore stride length)
-
Consider the buffering
example discussed in class. Acetic acid (CH3COOH) and acetate (CH3COO-) form a buffer system. Which one of the buffer components would decrease in
concentration if we were to add a strong
acid to the solution containing the
buffer?
CH3COO-
-
Which of the following
linkages would you expect to find at a branch point in glycogen or amylopectin?
α-1,6-glycosidic linkage
-
In what important way does a competitive
inhibitor differ from an allosteric inhibitor?
- A competitive inhibitor binds to the active site,
- whereas an allosteric inhibitor binds to a site other than the active site.
-
Recall Pasteur's experiment on spontaneous
generation. If he had just warmed the nutrient-rich broth, rather than boiled
it, what would have been the likely outcome of his experiment?
- Cells would have appeared in
- both flasks.
-
Cells would have appeared in
both flasks.
- It has two more protons than
- electrons.
-
An atom has five electrons in its valence shell.
How many single covalent bonds would you expect it to form in most
circumstances?
three
-
What holds electrons in a
covalent bond?
- The negative charges on the electrons are attracted by
- the positive charges on both nuclei.
-
Why are polymerization reactions endergonic?
-
You isolate a molecule and
determine it is nonpolar. Based on this
property, the molecule is largely composed of the elements _____.
-
How do the α and β forms of
glucose differ?
- Their ring structures differ in the location of a hydroxyl group.
-
Consider the buffering
example discussed in class. Acetic acid (CH3COOH) and acetate (CH3COO-) form a buffer system. Which one of the buffer
components would increase in
concentration if we were to add a strong
base to the solution containing the
buffer?
CH3COO-
-
A restriction enzyme cuts which particular molecule we discussed in class?
DNA
-
Nitrogen (N) normally forms
only three covalent bonds because it has a valence of five. However, ammonium
has four covalent bonds, each to a
different hydrogen (H) atom (H has a valence of one). Make a sketch of this molecule. Count the number of electrons
in your sketch. Compare this number to the number of valence electrons in one N and four H's. What do you predict to be the charge on this molecule?
+1
-
Enzymes that readily break starch apart cannot
hydrolyze the glycosidic linkages found in cellulose. Why is this logical?
- The geometry of the bonds is different, and the shapes
- of enzyme active sites are highly specific.
-
You disrupt all hydrogen
bonds in a protein. What level of
structure will be preserved?
primary structure
-
Nucleic acids have a definite polarity, or
directionality. Stated another way, one end of the molecule is different from the other end. How are these ends described?
- One end has an unlinked 3’ carbon; the other end has
- an unlinked 5’ carbon.
-
You disrupt all hydrogen
bonds in a protein. What level of
structure will be preserved?
primary structure
-
Why do chemical reactions tend to speed up when heat is applied to the reaction mixture
- A)
- The reactants move faster. B) The reactants collide more
- often.
C) The reactants have greater energy.
-
If you were going to develop a new antibiotic
against bacteria, you would probably need to become an expert on which of these
carbohydrates?
peptidoglycan
-
The lock-and-key analogy for enzymes applies to the _____.
- specificity of enzymes binding
- to their substrate
-
On
the tree of life, the branch leading to animals is closer to fungi than it is to the branch leading to land plants. Which of the following
statements is correct?
- Animals and fungi are more closely related to each
- other than animals are to land plants.
-
An enzyme has a total of four active sites. When you denature the molecule and
study its composition, you find that
each active site occurs on a different
polypeptide. Which of the following hypotheses does this observation support?
The protein has quaternary structure.
-
What type of interaction is directly responsible
for the formation of protein secondary structure?
- hydrogen bonds between sections of the polypeptide
- backbone
-
Which of the following best describes DNA's
secondary structure
double antiparallel helical strands
-
If the primary structure of a protein is
- any higher level folding of the protein will be
- incorrect.
-
You have isolated a previously unstudied protein, identified its complete structure in detail, and determined that it catalyzes the breakdown of a large substrate. You notice it has two binding sites. One of these is large, apparently the bonding site for the large substrate; the other is small, possibly a binding site for a regulatory molecule. What do these findings tell you about the mechanism of this protein?
- It is probably an enzyme that works through allosteric
- regulation.
-
What feature of mononucleotides provides the energy needed for polymerization when nucleic acids are formed?
their phosphate groups
-
Enzyme-catalyzed reactions increase in rate very
rapidly at low substrate concentrations but plateau at higher substrate concentrations Why?
- At high substrate concentrations, the enzyme molecules
- present are working at maximal speed and are unable to further increase the rate of reaction.
-
Complementary base pairing explained Chargaff's findings—the fact that the number of cytosines in a DNA sample equals the
number of guanines, and the number of thymines equals the number of adenines.
Complementary base pairing is the formation of hydrogen bonds between antiparallel strands of the DNA molecule. Which statement regarding complementary base pairing is correct?
- In DNA, the purine base adenine (A) always pairs with
- the pyrimidine base thymine (T).
-
What forms the "backbone" of a nucleic acid?
- a chain of sugar and phosphate groups, linked through
- phosphodiester bonds
-
The type of bond that forms
between a 3’-OH (hydroxyl) group of one nucleic acid and the 5’-P (phosphate)
group of another nucleic acid is called a _________________ bond.
phosphodiester
-
What is gel electrophoresis used for?
- B)
- to separate macromolecules such as DNA by size
- D) to
- separate macromolecules such as DNA by charge
-
Dairy cattle were unknown in Thai culture until recently, and 97% percent of Thai people are lactose intolerant as adults.
Which explanation for such widespread lactose intolerance is most likely
correct?
- Evolutionarily, producing an enzyme to break down a
- sugar that will never be encountered is wasteful.
-
A glycosidic linkage is analogous to which of the following in proteins?
a peptide bond
-
Environments all over the world are changing as
a result of global warming. Could this influence natural selection?
- Yes. Traits that help individuals produce more
- offspring in warmer environments will increase in frequency.
-
When nucleotides polymerize to form a nucleic
acid _____.
- a covalent bond forms between the sugar of one
- nucleotide and the phosphate of a second
-
What does it mean to say that a molecule has an optical isomer?
- It has two mirror-image forms, which cannot be exactly
- superimposed on each other.
-
Sickle-cell anemia results when valine replaces
glutamate at position 6 of the β-globin subunit of hemoglobin. The sickling seen in red blood cells with the defective hemoglobin subunit affects the _____.
primary structure of hemoglobin
-
Agrobacterium is a type of bacteria that infects plants and causes them to form tumors. You are asked to determine how long a plant must be exposed to the bacteria to become infected. Which of the following experiments will provide the best data for that question?
determining the number of tumors formed on a plant depending on how long it is exposed to Agrobacterium
-
Forensic science uses genetic fingerprinting
techniques to identify individuals who may or may not have been present at crime scenes. These techniques identify unique patterns present in the DNA of each individual. What are these unique patterns based upon?
- a) variable tandem nucleotide
- repeats present in the individual’s DNA
- c) restriction digestion of a person’s genetic material
-
Several of the molecules called vitamins act as
enzyme cofactors. Vitamin deficiencies cause disease. What is the most direct explanation for this?
- If cofactors are missing, enzymes cannot function
- properly, and important reaction products will be absent from cells.
-
How does primary protein
structure affect the function of protein enzymes?
Substrates interact with R-groups at the enzyme's active site.
-
Both starch and cellulose are glucose polymers.
Why can animals easily degrade starch, but not cellulose?
- Animals have the enzymes to degrade a-1,4-glycosidic
- bonds, but not b-1,4-glycosidic bonds.
-
The concept of ______________________ explains why antibiotics like penicillin and antimicrobial substances like lysozyme kill
or inhibit the growth of bacteria without a similar effect upon the infected host.
selective toxicity
-
Which of the following linkages would you expect to find at a branch point in glycogen or amylopectin? (Hint: the hydroxyl group
of the sugar monomers in this polysaccharide are located below the “plane” of
carbon #1)
α-1,6-glycosidic linkage
-
Consider the following reaction at equilibrium:
CO2 + H2O ↔ H2CO3. What would be
the effect of adding additional H2CO3?
- drive the equilibrium dynamics to the left and H2CO3
- levels will decrease
-
You've been asked to analyze a reaction that
took place at 300 K. ∆H was -150 and ∆S was +0.4. Is the reaction endothermic or exothermic?
exothermic
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