T
tommy
Guest
I have no idea where to begin, some help/partial answers would be grateful.
1. Aspirin is acetylsalicylic acid, which is shown below in its un-ionized form. The pK for the ionization of
acetylsalicylic acid is 3.5, and only the ionized form is absorbed in the body at a significant rate.
a. Draw acetylsalicylate (the ionized form of aspirin).
b. If the pH in the stomach 2.0, and the total concentration of aspirin is 1.7 mM, what is the concentration of acetylsalicylate?
c. What is the concentration of acetylsalicylate in the small intestine where the pH is 6.0?
d. Based on your answers, in what organ do you think ingested aspirin is absorbed?
2. Draw the tripeptide RAM in its predominant ionization state at pH 7.35, and calculate its pI.
3. Draw (S)-serine and (R)-cysteine as Fisher projections. Are they isosteric (i.e., do equivalent
functional groups occupy the same positions in space)?
4. Prion diseases are neurodegenerative pathologies
that arise spontaneously or through hereditary or
infectious transmission. The transmissible agent is
generally believed to be the protein PrPC, which is
nonpathogenic; however, it converts into a
pathogenic form, PrPSc, that is insoluble and has a
very high -sheet content. High resolution
structural data is available only for PrPC. Examine
the Ramachandran plot for PrPC and describe its
secondary structure.
5. . Where do new enzymes come from? Some bacteria have acquired the ability to metabolize man-
made chemicals. For example, tetrachlorophenol (TCP) did not exist in the environment before 1936
when it was introduced as a wood preservative, yet the bacterium Sphingomonas chlorophenolica
can metabolize TCP. One of the enzymes in the TCP degradative pathways is
tetrachlorohydroquinone dehalogenase (TCHQ dehalogenase). Examine the partial primary
sequences for TCHQ dehalogenase and several other enzymes and the structures of their substrates
shown on the following page. To which enzyme is TCHQ dehalogenase most closely related?
Explain your answer.
1. Aspirin is acetylsalicylic acid, which is shown below in its un-ionized form. The pK for the ionization of
acetylsalicylic acid is 3.5, and only the ionized form is absorbed in the body at a significant rate.
a. Draw acetylsalicylate (the ionized form of aspirin).
b. If the pH in the stomach 2.0, and the total concentration of aspirin is 1.7 mM, what is the concentration of acetylsalicylate?
c. What is the concentration of acetylsalicylate in the small intestine where the pH is 6.0?
d. Based on your answers, in what organ do you think ingested aspirin is absorbed?
2. Draw the tripeptide RAM in its predominant ionization state at pH 7.35, and calculate its pI.
3. Draw (S)-serine and (R)-cysteine as Fisher projections. Are they isosteric (i.e., do equivalent
functional groups occupy the same positions in space)?
4. Prion diseases are neurodegenerative pathologies
that arise spontaneously or through hereditary or
infectious transmission. The transmissible agent is
generally believed to be the protein PrPC, which is
nonpathogenic; however, it converts into a
pathogenic form, PrPSc, that is insoluble and has a
very high -sheet content. High resolution
structural data is available only for PrPC. Examine
the Ramachandran plot for PrPC and describe its
secondary structure.
5. . Where do new enzymes come from? Some bacteria have acquired the ability to metabolize man-
made chemicals. For example, tetrachlorophenol (TCP) did not exist in the environment before 1936
when it was introduced as a wood preservative, yet the bacterium Sphingomonas chlorophenolica
can metabolize TCP. One of the enzymes in the TCP degradative pathways is
tetrachlorohydroquinone dehalogenase (TCHQ dehalogenase). Examine the partial primary
sequences for TCHQ dehalogenase and several other enzymes and the structures of their substrates
shown on the following page. To which enzyme is TCHQ dehalogenase most closely related?
Explain your answer.