a. It will convert completely to the linear form. b. It will remain in solution,
ID: 888121 • Letter: A
Question
a. It will convert completely to the linear form.
b. It will remain in solution, as is.
2. Which statement about stereoisomers is false?
a. D- and L-isomers are mirror images of each other.
b. Epimers can interconvert rapidly in solution.
c. Anomers freely interconvert in solution through a linear intermediate.
d. Some hexoses can interconvert between pyranose and furanose forms.
3. Which feature of the bacterial peptidoglycan is not essential for its structural stability?
a. N-acetylmuramic acid.
b. D-amino acids.
c. D-monosaccharides.
d. L-amino acids such as lysine.
4. Which of the following does not accurately describe glycosylation sites of proteins?
a. In loops or turns
b. Asn, Ser, or Thr residues
c. On the surfaces of proteins
d. Buried residues inside proteins
5. Which is not a structural component of peptidoglycan?
a. Disaccharide
b. Pentaglycine
c. Tetrapeptide
d. Sulfate
Explanation / Answer
1. Which of the following will happen to a solution of pure -D-glucopyranose?
the correct answer is d.
d. It will begin converting to the -anomer, eventually reaching an equilibrium concentration of 63.6 % due to mutarotation .
The change in the optical rotation at the equilibrium point between two anomers interconvert is known as mutarotation.
2. Which statement about stereoisomers is false?
The correct answer is b.
b. Epimers can interconvert rapidly in solution.
Epimerisation can be spontaneous means generally a slow process. it can be catalyzed by enzyme for example epimerization between the sugars N-acetylglucosamine and N-acetylmannosamine, is catalyzed by Renin-Binding Protein.
3. Which feature of the bacterial peptidoglycan is not essential for its structural stability?
d. L-amino acids such as lysine.
The main structural features of bacterial peptidoglycan are linear glycan chains interlinked by short peptides. The glycan chains are composed of alternating units of N-acetylglucosamine (GlcNAc) and N-acetylmuramic acid (MurNAc).
The chemical structure of peptidoglycan consists of four amino acids, with the best-studied cell walls containing L-alanine, D-alanine, D-glutamic acid and diaminopimelic acid.
D-monosaccharides are structural elements in the cell walls of bacteria (peptidoglycan or murein), plants (cellulose) and animals (chitin).
Hence the correct answer is d. d. L-amino acids such as lysine.
4. Which of the following does not accurately describe glycosylation sites of proteins?
d. Buried residues inside proteins
The correct ans is d. Buried residues inside proteins do not accurately describe glycosylation sites of proteins because they are sugars.
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