Have a test tomorrow and the professors answer from the test key doesn’t address

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Have a test tomorrow and the professors answer from the test key doesn’t address the question. Will pay in bitcoin for answer plz help Essay Question: (10 points 4. Lactase is an enzyme that breaks lactose sugar in milk. A mutation occurs in the gene for lactase that results in a leucine (a hydrophobic amino acid) being substituted for an arginine (a positively charged amino acid). Do you think that the mutant lactase will function similarly to the normal lactase? The flow of information : DNA mRNA Protein a. Explain how this change would affecet the Primary, Secondary, Tertiary and Quaternary structure of the protein. Primary structure: Linked series of amino acids with a unique sequence Secondary structure: Coils and folds resulting from the hydrogen bonds between the repeatin constituents of the polypeptide backbone Alpha helix: Delicate coil held together by hydrogen bonding between every fourth amino acid - Beta pleated sheet: Two or more strands of the polypeptide chain lying side by side, connected by hydrogen bonds between parts of the two parallel polypeptide backbones Tertiary structure: Overall shape of the polypeptide resulting from interactio chains (R groups) of the various amino acids ns between the si Quaternary structure: Overall protein structure that results from the aggregation of these polypeptide subunits b. What are the External factors that can affect protein structure? The function of a protein is determined by its shape. When the protein is not correctly folded its shape that is called denaturation. So the external factors that affect the protein structure from functioning optimally are: Biol 1406 Sp- 2018 P.Richards

Explanation / Answer

Mutation at a gene may or maynot alter the function of protein translated or expressed. However in the condition mentioned above , substitution of leucine for arginine would change the function of mutant.

Sufficient evidences have been gained in this regard. Arginine residue which is found on transmembrane segment at 302 has been implicated in H+ and/or sugar recognition. However following its substitution with leucine, resulted in impaired ability to transport the galactosides as evidenced by their poor growth on minimal plates supplemented with lactose or melibose and result in lactose intolerance.

The effect of mutation on :

Primary structure: The sequence of amino acids would change at the point of substitution.

Secondary structure: Since both of them share different chemical properties, their would be change in secondary structure

Similarly for tertiary and quaternary structures, The active site formed in the tertiary structure may get altered and spatial arrangement of polypeptide change might also change due to altered sequence.

The external factors affecting :

1) pH: Several amino acids contain functional groups having side chains which can gain or lose a proton. This may lead to alteration of charge of protein leading to charge charge repulsion and attraction between amino acids which were previously non attracting.

Temperature : High temperature can disrupt the hydrogen and hydrophobic interactions in the structure.

3) Reducing/oxidizing substances: proteins have disulfide linkages which ensure protein folding . Disruption of these bonds or interactions may lead to improper unfolding.

4) Small molecules like urea , alcohol which may interupt and cause misfolding

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