BCHM 307 Exam 1 Purdue
A cook decides to flavor a gelatin dessert with fresh papaya and pineapple. The fruits are added
to a solution of gelatin in hot water, then the mixture is allowed to cool. What is the result and
how could the cook have avoided this? (Hint: Gelatin is a food product obtained from the
thermal degradation of collagen.) - ANS--adding papaya or pineapple means the proteolytic
enzymes present in the fruit will degrade the collagen/gelatin and prevent it form setting
-if the enzymes in the fruit and heated prior to adding to the gelatin, then the gelatin would set
as expected. Using canned fruit wouldn't cause a problem due to being heated during the
canning process
A diploid organism with 30,000 kb haploid genome contains 19% T residues. Calculate the the
number of A, C, G, and T residues in the DNA of each cell in this organism. - ANS-A, T= (.19)
(6x10^7) = 1.14x10^7
C,G= (.31) (6x10^7) = 1.86 x 10^7
A friend tells you that she plans to eat a lot of celery because she heard that the digestion of
celery consumes more calories than the food contains, and this will help her to lose weight. How
do you respond? - ANS-Celery is mainly cellulose and water, neither of which provides nutritive
calories. Humans do not have beta glucosidase enzymes and cannot hydrolyze the beta
glycosidic bonds linking the glucose residues in cellulose. Since cellulose is not digested, the
body does not spend any energy to further the process it. Foods like celery contribute roughage,
or fiber to the diet but these foods neither provide nor cost the body much in the way of energy.
A Glu residue in a receptor protein is altered to Ala in a site-directed mutagensis experiment.
Binding of the ligand to the mutant receptor decreases 100 fold. What does this tell you about
the interaction between the ligand and the receptor. - ANS-Its possible that the ligand has a
positive charge and forms in an ion pair with the negatively charged GLu on the receptor. When
the Glu is mutated to Ala, the negative charge on the receptor is lost and the ion pair between
the receptor and the ligand can no longer form.
A healthy diet must include some protein. Assuming you had a way to measure the amount of
each element in a sample of food, which element would you measure in order to tell whether the
food contained protein? - ANS-Assuming you had a way to measure each element in a food
sample, you should measure for the element nitrogen if determining the amount of protein.
Protein is the only macronutrient that contains nitrogen.
A soccer coach keeps a couple of instant cold packs in her bag in case one of her players
suffers a muscle injury. Instant cold packs are composed of a plastic bag containing a smaller
water bag and solid ammonium nitrate. In order to activate the cold pack, the bag is kneaded
until the smaller water bag breaks, which allows the released water to dissolve the ammonium
, nitrate. the equation for the dissolution of ammonium nitrate in water is shown below. How does
the cold pack work. - ANS-The positive charge indicates that the dissolution of ammonium
nitrate is an endothermic process. When the ammonium nitrates dissolves in water, it absorbs
heat from its surroundings, making its surroundings cooler, making it useable is a cold pack for
injuries.
Amino acids such as glycine, alanine, and valine are not known to particiapte directly in
acid-base or covalent catalysis.
a. Explain why this is the case.
b. Mutating a glycine, alanine, or valine residue in an enzymes active site can still have dramatic
effects on catalysis. Why? - ANS-a. Gly, Ala, and Val have side chains that lack the functional
groups required for acid-base or covalent catalysis
b. mutating one of these residues may alter the conformation at the active site enough to disrupt
the arrangement of other groups that are involved in catalysis
An Asp residue in the RNase T1 enzyme is protonated. Does this make the side chain more or
less likely to form hydrogen bonds with neighboring amino acid side chains in the enzyme. -
ANS-The Asp residue is more likely to form hydrogen bonds when protonated. The carboxylic
acid side chain can participate in three hydrogen bonds, whereas the carboxylate group can
participate in only two
Certain bacteria synthesize cyclic tetrapeptides.
a. Estimate the net charge at pH 7.0 of such a compound that consists of two Pro and two Tyr
residues.
b. If the peptide were linear rather than cyclic, what would be the net charge - ANS-The net
charge is 0
If the molecule were linear, it would contain a free amino group (+1 charge) and a free
carboxylate group (-1 charge) but its net charge would still be 0
Daniel Koshland has noted that hexokinase undergoes a large conformational change on
substrate binding, which apparently prevents water from entering the active site and
participating in hydrolysis. However, the serine proteases do not undergo large conformational
changes on substrate binding. Explain. - ANS-In a serine protease, there is no need to exclude
water from the active site, since it is a reactant for the hydrolysis reaction catalyzed by the
enzyme
Discuss the shortcomings of the following definitions for a gene:
a. A gene is the information that determines an inherited characteristic such as flower color.
b. A gene is a segment of DNA that encodes a protein.
c. A gene is a segment of DNA that is transcribed in all cells - ANS-a. an inherited characteristic
could be determined by more than one gene
b. Some sequences of DNA encode RNA molecules that are not translated into protein
A cook decides to flavor a gelatin dessert with fresh papaya and pineapple. The fruits are added
to a solution of gelatin in hot water, then the mixture is allowed to cool. What is the result and
how could the cook have avoided this? (Hint: Gelatin is a food product obtained from the
thermal degradation of collagen.) - ANS--adding papaya or pineapple means the proteolytic
enzymes present in the fruit will degrade the collagen/gelatin and prevent it form setting
-if the enzymes in the fruit and heated prior to adding to the gelatin, then the gelatin would set
as expected. Using canned fruit wouldn't cause a problem due to being heated during the
canning process
A diploid organism with 30,000 kb haploid genome contains 19% T residues. Calculate the the
number of A, C, G, and T residues in the DNA of each cell in this organism. - ANS-A, T= (.19)
(6x10^7) = 1.14x10^7
C,G= (.31) (6x10^7) = 1.86 x 10^7
A friend tells you that she plans to eat a lot of celery because she heard that the digestion of
celery consumes more calories than the food contains, and this will help her to lose weight. How
do you respond? - ANS-Celery is mainly cellulose and water, neither of which provides nutritive
calories. Humans do not have beta glucosidase enzymes and cannot hydrolyze the beta
glycosidic bonds linking the glucose residues in cellulose. Since cellulose is not digested, the
body does not spend any energy to further the process it. Foods like celery contribute roughage,
or fiber to the diet but these foods neither provide nor cost the body much in the way of energy.
A Glu residue in a receptor protein is altered to Ala in a site-directed mutagensis experiment.
Binding of the ligand to the mutant receptor decreases 100 fold. What does this tell you about
the interaction between the ligand and the receptor. - ANS-Its possible that the ligand has a
positive charge and forms in an ion pair with the negatively charged GLu on the receptor. When
the Glu is mutated to Ala, the negative charge on the receptor is lost and the ion pair between
the receptor and the ligand can no longer form.
A healthy diet must include some protein. Assuming you had a way to measure the amount of
each element in a sample of food, which element would you measure in order to tell whether the
food contained protein? - ANS-Assuming you had a way to measure each element in a food
sample, you should measure for the element nitrogen if determining the amount of protein.
Protein is the only macronutrient that contains nitrogen.
A soccer coach keeps a couple of instant cold packs in her bag in case one of her players
suffers a muscle injury. Instant cold packs are composed of a plastic bag containing a smaller
water bag and solid ammonium nitrate. In order to activate the cold pack, the bag is kneaded
until the smaller water bag breaks, which allows the released water to dissolve the ammonium
, nitrate. the equation for the dissolution of ammonium nitrate in water is shown below. How does
the cold pack work. - ANS-The positive charge indicates that the dissolution of ammonium
nitrate is an endothermic process. When the ammonium nitrates dissolves in water, it absorbs
heat from its surroundings, making its surroundings cooler, making it useable is a cold pack for
injuries.
Amino acids such as glycine, alanine, and valine are not known to particiapte directly in
acid-base or covalent catalysis.
a. Explain why this is the case.
b. Mutating a glycine, alanine, or valine residue in an enzymes active site can still have dramatic
effects on catalysis. Why? - ANS-a. Gly, Ala, and Val have side chains that lack the functional
groups required for acid-base or covalent catalysis
b. mutating one of these residues may alter the conformation at the active site enough to disrupt
the arrangement of other groups that are involved in catalysis
An Asp residue in the RNase T1 enzyme is protonated. Does this make the side chain more or
less likely to form hydrogen bonds with neighboring amino acid side chains in the enzyme. -
ANS-The Asp residue is more likely to form hydrogen bonds when protonated. The carboxylic
acid side chain can participate in three hydrogen bonds, whereas the carboxylate group can
participate in only two
Certain bacteria synthesize cyclic tetrapeptides.
a. Estimate the net charge at pH 7.0 of such a compound that consists of two Pro and two Tyr
residues.
b. If the peptide were linear rather than cyclic, what would be the net charge - ANS-The net
charge is 0
If the molecule were linear, it would contain a free amino group (+1 charge) and a free
carboxylate group (-1 charge) but its net charge would still be 0
Daniel Koshland has noted that hexokinase undergoes a large conformational change on
substrate binding, which apparently prevents water from entering the active site and
participating in hydrolysis. However, the serine proteases do not undergo large conformational
changes on substrate binding. Explain. - ANS-In a serine protease, there is no need to exclude
water from the active site, since it is a reactant for the hydrolysis reaction catalyzed by the
enzyme
Discuss the shortcomings of the following definitions for a gene:
a. A gene is the information that determines an inherited characteristic such as flower color.
b. A gene is a segment of DNA that encodes a protein.
c. A gene is a segment of DNA that is transcribed in all cells - ANS-a. an inherited characteristic
could be determined by more than one gene
b. Some sequences of DNA encode RNA molecules that are not translated into protein
