Carbohydrates
Undergraduate Questions (50 Pts)
1. (4 pts) A chemist working in a pharmaceutical lab synthesized a new drug as a racemic mixture. Why is it important that she separates the two enantiomers and test each for its biological activity?
2. (6 pts) Phosphoric acid (H3PO4) has three dissociable protons, with the pKa’s shown below. Which form of phosphoric acid predominates in a solution at pH 4? Explain your answer. Acid pKa H3PO4 2.14
H2PO4– 6.86
HPO42– 12.4
3. (4 pts) Mutations may arise during DNA replication when mispairing occurs as a result of the transient formation of a rare tautomeric from of a base, such as the imino tautomer of adenine shown below. Draw the structure of a base pair with proper Watson-Crick geometry that contains a rare imino tautomer of adenine (see the structure below). What base sequence change such a mispairing would cause?
[pic]
4. (4 pts) Methanol (wood alcohol) is highly toxic because it is converted to formaldehyde in a reaction catalyzed by the enzyme alcohol dehydrogenase:
NAD+ + methanol → NADH + H+ + formaldehyde
Part of the medical treatment for methanol poisoning is to administer ethanol (ethyl alcohol) in amounts large enough to cause intoxication under normal circumstances.
Explain this treatment in terms of what you know about examples of enzymatic reactions.
5. (4 pts) The number of structurally different polysaccharides that can be made with 20 different monosaccharides is far greater than the number of different polypeptides that can be made with 20 different amino acids even though both polymers contain an equal number of 100 total residues. Is the statement true or false? Explain your reasoning.
6. (4 pts) A plant breeder has developed a new frost-resistant variety of tomato that contains
1. (4 pts) A chemist working in a pharmaceutical lab synthesized a new drug as a racemic mixture. Why is it important that she separates the two enantiomers and test each for its biological activity?
2. (6 pts) Phosphoric acid (H3PO4) has three dissociable protons, with the pKa’s shown below. Which form of phosphoric acid predominates in a solution at pH 4? Explain your answer. Acid pKa H3PO4 2.14
H2PO4– 6.86
HPO42– 12.4
3. (4 pts) Mutations may arise during DNA replication when mispairing occurs as a result of the transient formation of a rare tautomeric from of a base, such as the imino tautomer of adenine shown below. Draw the structure of a base pair with proper Watson-Crick geometry that contains a rare imino tautomer of adenine (see the structure below). What base sequence change such a mispairing would cause?
[pic]
4. (4 pts) Methanol (wood alcohol) is highly toxic because it is converted to formaldehyde in a reaction catalyzed by the enzyme alcohol dehydrogenase:
NAD+ + methanol → NADH + H+ + formaldehyde
Part of the medical treatment for methanol poisoning is to administer ethanol (ethyl alcohol) in amounts large enough to cause intoxication under normal circumstances.
Explain this treatment in terms of what you know about examples of enzymatic reactions.
5. (4 pts) The number of structurally different polysaccharides that can be made with 20 different monosaccharides is far greater than the number of different polypeptides that can be made with 20 different amino acids even though both polymers contain an equal number of 100 total residues. Is the statement true or false? Explain your reasoning.
6. (4 pts) A plant breeder has developed a new frost-resistant variety of tomato that contains