SECTION C: Answer the following questions using complete sentences. 11. Explain

Question

SECTION C: Answer the following questions using complete sentences. 11. Explain why Homo sapiens are not considered model organisms. (10 pts) 12. You are given an unlabeled test tube and are told it is either a carbohydrate or a protein Describe how you can determine which type of macromolecule you have. (10 pts) 13. A transmembrane protein has 1000 amino acids. The seventh amino acid is found in between the tails of the cell membrane. Amino acid 36 is found on the outer surface of the protein and it interacts with the aqueous environment but would not form ionic bonds with other charged molecules. Amino acids 518 and 823 are covalently bonded to each other and contribute to the stabilization of the protein conformation. A weak hydrogen bond forms between amino acids 888 and 989 and they are found on the external surface of the protein. Identify each of the numbered amino acids by structural group and name. (NOTE: For this question, no two answers should be the same. For most positions, there are more than one specific amino acid that would be correct. Again, the probability that two students would come up with the exact same answer is EXTREMELY small.) (18 pt total;3 pts/amino acid)

Explanation / Answer

Ans. #11. Homo sapiens can’t be used as model organism for following reasons-

I. It’s extremely difficult to keep human under defined laboratory conditions against their will.

II. Relatively longer life-cycle and gestation period, and only one progeny (in general) per parturition.

III. Extremely complex tissues and organs like neurons and brain.

Etc.

#12. Add few drops of biuret reagent to the test tube. If the color changes from blue to purple, the sample contains protein. The biuret test involves the formation of Cu2+-peptide complex in which 4 peptide bond amine groups are complexed with 1 Cu2+ ions. The resultant complex is purple in color.

If the color of biuret reagent remains unchanged (blue), the given test solution contains carbohydrate.

#13. Seventh amino acid: Being located in the hydrophobic core (between the tails of cell membrane) of the membrane, the amino acid must have non-polar side chain. Amino acids with non-polar side chain exert hydrophobic interactions with non-polar fatty acid tails to result a stabilized entity.

Example- it can be any one of Val, Ile, Trp, Phe, Ala, etc.

# Amino acid 36: It interacts with aqueous environment but does not form ionic interactions. To do so, the side chain of amino acid must be unchanged and poplar. For example- Serine, threonine, etc.

# Amino acid 518 and 823: A covalent bond (disulphide bond) between the side chains of two residues only forms when they both are cysteine. So, both the residues must be cysteine.

# Amino acids 888 and 989: To occurs at external surface of protein, the residues must be polar because they need to interact with aqueous surrounding. To form hydrogen bonds, the side chain of these residues shall contain O-atom, N-atom as well as an H-atom linked to O- or N-atom.

These residues can be- serine, threonine, tryptophan.   

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