WGU C785 Biochemistry Unit Exam Questions & Answers Latest 2021/2022 1.Which level of protein structure is disrupted through the hydrolysis of peptide bonds?a.Primary b.Tertiary c.Secondary d.Quaternary Answer: A. The primary structure of a protein is the sequence of amino acids held together by peptide bonds.Peptide bonds are formed by dehydration reactions and disrupted by hydrolysis.
2.A mutation in the beta-hemoglobin gene, which results in the replacement of the amino acid glutamate in position 6 with the amino acid valine, leads to the development of sickle cell anemia.The structures of glutamate and valine are shown below.Amino acid structures of glutamate and valine If the beta hemoglobin gene in a patient with sickle-cell anemia were to be edited so that the valine in position 6 was replaced with a different amino acid, which replacement for valine would be expected to have the best clinical outcome, in theory, for the patient? (Assume the valine can potentially be replaced with any amino acid other than glutamate.)
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Answer: B. The original amino acid in a healthy patient is glutamate, which is negatively charged. The mutated amino acid is valine, which is non-polar. Valine is causing sickle cell anemia. The best amino acid to replace valine so that the patient is healthy again would be the one most like glutamate, so any negatively charged amino acid.Amino acid structure C is non-polar, not charged.
3.Secondary, tertiary, and quaternary levels of protein structure can all be impacted by exposing a protein to which treatment?a.Increase in the concentration of the protein in solution b.Placement of the protein in a solution with a low pH c.Addition of a reducing agent d.Change of a hydrophobic amino acid to a different hydrophobic amino acid Answer: B. The correct answer is “Placement of the protein in a solution with a low pH”. The addition of a reducing agent would only affect disulfide bonds in the side chains of polar amino acids containing SH. These types of bonds are only found in the tertiary and quaternary structure, not secondary structure.
4.An increase in beta-pleated sheet structure in some brain proteins can lead to an increase in amyloid deposit formation, characteristic of some neurodegenerative diseases. What is the primary biochemical process that follows the increase in beta-pleated sheet structure that leads to the development of the amyloid deposits?a.An increase in anaerobic metabolism of glucose in the brain b.Aggregation of the proteins in the brain c.An increase in glycogen formation in the brain cells d.Secretion of glucagon, leading to excessive ketogenesis Answer: B. The correct answer is “Aggregation of the proteins in the brain”. This question is describing changes in protein structure. Glycogen is a carbohydrate, not a protein, and is stored in the liver and muscles, not the brain. See Unit 6 for more information on glycogen.
5.Which level of protein structure is determined by the sequence of amino acids?a.Secondary structure b.Tertiary structure c.Primary structure d.Quaternary structure Answer: C. The correct answer is “Primary structure”. The primary structure of a protein is simply the sequence of amino acids held together by peptide bonds. The quaternary structure of a protein is when two or more polypeptide chains (“subunits”) work together to perform the function of the protein. The two or more polypeptide chains are held together by side chain interactions, including the hydrophobic effect, ionic bonds, disulfide bonds, and hydrogen bonds.
6.Which force is most influential in determining the secondary structure of a protein?a.Disulfide bonding b.Hydrophobic effect c.Hydrogen bonding d.Electrostatic interactions
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