SI questions

1. Autopsies of patients with Alzheimer disease show protein aggregates called neurofibrillary tangles and neuritic plaques in various regions of the brain. These plaques exhibit the characteristic staining of amyloid. Which of the following structural features is the most likely characteristic of at least one protein in these plaques? A. A high content of β-pleated sheet structure B. A high content of α-helical structure C. A high content of random coils D. Disulfide bond cross-links between polypeptide chains E. A low-energy native conformation

A.

1. In order for a cell to carry out its biologic functions, the intracellular reactions need to be directed to follow a certain pathway. Which one statement best describes the direction a chemical reaction will follow? A. A reaction with positive free energy will proceed in the forward direction if the substrate concentration is raised high enough. B. Under standard conditions, a reaction will proceed in the forward direction if the free energy ΔG0′ is positive. C. The direction of a reaction is independent of the initial substrate and product concentrations because the direction is determined by the change in free energy. D. The concentration of all of the substrates must be higher than that of all of the products for the reaction to proceed in the forward direction. E. The enzyme for the reaction must be working at >50% of its maximum efficiency for the reaction to proceed in the forward direction.

A.

1. Reactions in the cell with a positive ΔG0′ can proceed in the forward direction only if: A. the concentration of substrate is raised to high enough levels B. the concentration of products is raised to high enough levels C. An enzyme is added to the reaction D. A reaction with a positive G would never proceed in a forward direction.

A.

1. What is the difference between covalent and noncovalent interaction? A. Covalent bonds deal with shared electrons, while Noncovalent (NC) denotes attraction between opposite charges B. Covalent bonds are formed between molecules NC is formed between atoms C. Non-Covalent bonds is formed between molecules, while Covalent bond is formed between atoms D. Non-Covalent bonds deals with shared electrons while Covalent denotes attraction between opposite charges

A.

1. When a reaction has a positive change in enthalpy and negative change in entropy, the reaction is never spontaneous. A. True B. False

A.

1. A patient with hyperlipidemia has been counseled to reduce the saturated fats in his diet, so he has replaced butter with a butter substitute that he knows is made from a polyunsaturated oil. The manufacturer of this butter substitute has partially hydrogenated this product. Which one of the following is the best description of why this product was partially hydrogenated? a. The trans-fatty acids produced by commercial hydrogenation are very healthy in humans. b. Hydrogenation reduces the double bonds, creating a more saturated product, which is more marketable. c. Hydrogenation makes the product less expensive to produce. d. Hydrogenation reduces the cholesterol content of the oil. e. Hydrogenation increases the cholesterol content of the oil.

B.

1. A researcher is trying to design an antibiotic to kill bacteria but not harm any human cells. Which one of the following theoretically could be used for this purpose? A. A medication that inhibits reactions using only d-amino acids B. A medication that inhibits reactions using only l-amino acids C. A medication that inhibits reactions using only amino acids containing a β-amino group D. A medication that inhibits reactions using only amino acids containing a γ-amino group E. A medication that only inhibits reactions using only aromatic amino acids

B.

1. As a scientist you find an unknown sample and run some tests to identify this unknown sample. Molecular analysis found glycerol, fatty acids, phosphate and choline. Given this, which conclusion is most probable? A. It can be a sample of carbohydrate only. B. It can be a sample of phospholipid and fat. C. It is only phospholipid. D. It is only fat.

B.

1. When a reaction is exothermic, it is always spontaneous. A. True B. False

B.

1. Which is a characteristic of both an α-helix and a β-pleated sheet? A. Both can be anti-parallel structures. B. Both form interactions involving the oxygens of peptide bonds. C. Both are found only within multimeric proteins. D. Both are denatured when heat breaks peptide bonds.

B.

1. Which is a property of protein tertiary structure? A. Tertiary structures usually contain hydrocarbon R-groups in the interior of the protein where they can form hydrogen bonds. B. Tertiary structures usually contain hydroxyl R-groups on the exterior of the protein where they can favorably interact with water. C. A protein's tertiary structure can be predicted if the amino acid sequence is known by performing the Edman degradation. D. A protein's tertiary structure can be maintained by covalent salt bridges and non-covalent disulfide bridges.

B.

1. Eukaryotic cells possess an endoplasmic reticulum; however, prokaryotes lack an endoplasmic reticulum, or any other intracytoplasmic membrane bound structure. Thus, the endoplasmic reticulum most probably evolved from: A. the synthetic biology theory B. the big bang theory C. gradual evolution D. spontaneous regeneration E. endosymbiosis theory

C.

1. In which of the following cellular compartments is ionic bond strongest? A. Pure water B. Cytosol C. Core of a protein excluded from water D. Within salty sea water.

C.

1. The β-sheet structure can be described by which of the following? 1. It contains parallel chains which are stabilized only by hydrophobic interactions between side chains of amino acids 2. It is pleated because the peptide bond is not planar 3. The structure has the side chains of adjacent amino acids alternating above and below the plane of the sheet 4. The hydrogen bonds is formed between the backbone of two strands lying adjacent to each other. A. Answers 1, 2 and 3 are correct B. Answers 1 and 3 are correct C. Answers 2, 3 and 4 are correct D. Only answer 4 is correct E. All of the answers are correct

C.

1. Which is a difference between an α-helix and a β-pleated sheet? A. An α-helix is a right-handed structure containing disulfide bonds while a β-pleated sheet is a left-handed structure containing ionic bonds. B. An α-helix has a relatively extended spiral shape while a β-pleated sheet has a relatively compact zig-zag shape. C. An α-helix has non-covalent bonds between amino acids near each other in the sequence while a β-pleated sheet has non-covalent bonds between amino acids far apart in the sequence. D. An α-helix contains mainly amino acids with polar R-groups while a β- pleated sheet contains mainly amino acids with non-polar R-groups.

C.

1. Which molecular chaperone binds specifically to hydrophobic residues in nascent polypeptides, as they are being synthesized? A. HSP47 B. HSP60 C. HSP70 D. HSP35

C.

1. Parkinson's, Creutzfeldt Jacob, and Alzheimer's disease are all associated with misfolded proteins. After Dr. Torres's class, you are inspired to take on the world and combat protein folding disease. Based on what we discussed in class, which one of the following would be an ill-advised therapeutic approach to circumventing protein folding diseases? A. A drug that act as a molecular chaperone, that guides misfolded proteins to their native state. B. A drug that can potentially increase the alpha helix content of proteins with abnormal beta sheet content C. Gene therapy to replace defective genes responsible for inducing the synthesis of prions D. A drug that can act as a protease (enzymes that digest unwanted proteins in cells)

D.

1. The value of ΔG for a reaction can be influenced by all of the following except: A. the initial concentration of substrates and products B. by temperature C. by Ph D. By Enzymes

D.

1. Which is a characteristic of protein quaternary structure? A. A protein composed of identical subunits has quaternary structure but not tertiary structure. B. A protein composed of non-identical subunits contains two polypeptide chains with opposite charges. C. The quaternary structure of a multimeric protein always includes covalent crosslinks between the subunits. D. The quaternary structure of a multimeric protein always depends upon the primary structure of the subunits.

D.