BioChem C785 module 2 quiz(2021/2022)

Which image below shows the carboxyl group of an amino acid circled? Answer- An amino acid consists of an amino group, carboxyl group, a hydrogen and a variable side chain arranged around a central alpha carbon atom. The backbone of an amino acid is the entire amino acid molecule minus the variable side chain. The carboxyl group of an amino acid is shown as COO_ or COOH attached to a central alpha carbon atom of the amino acid. Which of the following statements is NOT true about the different levels of a protein structure? Answer- The interactions between the side chains of the amino acids make up the secondary level structure of a protein Which statement reflects the role that protein structure can play in the disease process? Answer- Mutation of an active site amino acid changes an enzyme's ability to bind a substrate. Aggregation of the proteins is the main reason behind many neurodegenerative diseases. Which one of the following mutations will likely cause a neurodegenerative disease? Answer- Replacing a polar amino acid with a non polar amino acid Which pair (protein interaction and technique) will likely denature a protein? Answer- Hydrogen bonds/ionic bonds: Change in pH Which one of the following statements is NOT true about protein structure and stability? Answer- Protein structure is not stabilized by the hydrophobic effect Alkaline phosphatase is produced by bone and liver in the human body. The amount of alkaline phosphatase in blood can help identify if a patient potentially has certain types of bone and/or liver-related disease, including Paget disease, hepatitis, and certain types of cancer. The optimal pH range for alkaline phosphatase activity is a pH of 8.0 to 10.0. What happens to the activity of the alkaline phosphatase at a pH of 2? Answer- Significantly decreases Inhibitors that have a similar structure to a substrate of an enzyme are most likely to bind to the enzyme's ____________ and be a ____________ inhibitor. Answer- active site, competitive When an inhibitor binds reversibly to a site of the enzyme that is not the active site, what type of inhibition results? Answer- Noncompetitive inhibition Chymotrypsin is a digestive enzyme that has optimal activity at a pH of 7.8 and a temperature of 37oC. Which of the following statements is true? Answer- The reaction rate for chymotrypsin at a pH of 9.5 is lower than the reaction rate for chymotrypsin at a pH of 7.8. Replacing an asparagine with leucine at a specific position on an enzyme, as shown below, leads to a neurodegenerative disease. What could asparagine be mutated to that would have less impact on the protein structure and function of the enzyme than the leucine mutation? Answer- Generally, mutations to amino acids that are similar in nature and structure to the original amino acid have the least impact on the protein's function. For that reason, changing the asparagine to glutamine, another polar amino acid with a similar R group, is likely to have the least impact. Which image below shows the side chain of an amino acid circled? Answer- An amino acid has a central alpha carbon. And around this carbon there are four groups known as the alpha group, carboxyl group, hydrogen atom and the variable side chain. The variable side chain is often represented as R. The side chain can range from a simple H as in the case of glycine to some complex ringed structures as in the case of tryptophan. Typically, a side chain can be identified by first isolating the backbone (the central carbon with the hydrogen, amino and the carboxyl group). The amino acid molecule minus backbone is the side chain. For the pathway below, which of the following statements is NOT true? Answer- Inhibition of Enzyme 1 will lead to increased levels of Molecule C. Enzymes increase the rate of reaction by doing which of the following: Answer- Decreasing the activation energy of a reaction. The concept of the induced fit applies to which part of the enzymatic cycle? Answer- Enzyme-Substrate Complex Below is a depiction of the enzyme cycle for sucrase. Which of the following is NOT true. Answer- Water is a product of sucrase In the reaction provided below, glucose-6-phosphate accumulates in the cell and binds to hexokinase at a site that is distinct from the active site. This prevents hexokinase from binding to its substrate. Following inhibition of hexokinase, what happens to the amount of pyruvate in the cell? Answer- Decreases In the reaction provided below, glucose-6-phosphate accumulates in the cell and binds to hexokinase at a site that is distinct from the active site. This prevents hexokinase from binding to its substrate. What type of inhibition is occurring in this example? Answer- Noncompetitive inhibition Which amino acid would you be most likely to find on the interior of a protein? Answer- phenylalanine What kind (class) of amino acid is shown below? Answer- Non-polar (hydrophobic) Interactions between these two amino acids help stabilize the structure of a certain protein.What kind of interaction is this? Answer- ionic bond In a certain protein, a mutation occurred that changed the first member of this glutamate-arginine pair from glutamate to lysine. Which amino acid from the choices below could the arginine be mutated to to restore the original interaction? Answer- An ionic bond is formed between the negative and positive charged amino acid side chains. Which kind of interaction between their side chains can the pair of amino acids below form? Answer- Hydrogen bond Which pair of amino acids below can form an ionic bond? Answer- Ionic bonds are typically formed between the amino acid side chains with opposing charges. Notice that this particular amino acid pair does not contain any charge (- or +) in their side chains. The correct answer is the option-option 3. A _________________ reaction builds a polypeptide, where as a ______________ reaction breaks a polypeptide. Answer- dehydration, hydrolysis