Chem Exam 2 (A) Name

Transcription

1 Chem 4511 Exam 2 (A) Name No credit will be given for answers (or work) that are on the backsides of the pages. You may use the backsides as scratch paper, but put all of your answers on the front sides.

2 (Multiple choice are 2 points each) 1. Contractions in muscles are activated as a result of A) a decrease in the Ca 2+ concentration in cytoplasm B) a decrease in the Ca 2+ concentration in nucleus C) an increase in the Ca 2+ concentration in cytoplasm D) an increase in the Ca 2+ concentration in nucleus E) nothing related to Ca 2+ concentration 2. The Bohr effect describes the observed increased in O 2 affinity by Hb when A) O 2 concentration decreases B) BPG concentration increases C) BPG concentration decreases D) ph decreases E) ph increases 3. There are five different classes of antibodies produced by our immune system. Among them IgG is one type having a molecular mass of approximately 150 kda. How many subunits the IgG have? A) 1 heavy chain and 1 light chain B) 1 heavy chain, 1 light chain and a J chain C) 2 heavy chains and 2 light chains D) 2 heavy chains, 2 light chains, and a J chain E) 4 heavy chains and 4 light chains 4. Glucose, an aldohexose has stereoisomer(s). A) 1 B) 2 C) 4 D) 8 E) Ribulose, a ketopentose, has stereoisomer(s). A) 1 B) 2 C) 4 D) 8 E) Actin and myosin are the two main proteins participating in muscular contractions. When a muscle contracts A) actin filaments are pushed towards the Z disk by myosin B) actin filaments are pulled towards the M disk by myosin C) myosin is pushed towards Z disk by actin D) myosin is pulled towards M disk by actin E) None of the answers above are correct. 7. Carbonic anhydrase catalyzes A) bicarbonate hydration, resulting in the formation of carbonic acid. B) carbamates hydrolysis with associated proton consumption C) carbamates formation with the associated proton release D) carbon dioxide reduction with associated consumption of protons. E) carbon dioxide hydration, forming bicarbonate and protons. 8. Which of the following statements is true? A) Fatty acids with more than 18 carbons are the most common. B) Synthesis of fatty acids occurs in 2 carbon units. C) Fatty acids with conjugated double bonds very common in plants. D) In higher plants and animals, C 12 and C 14 species predominate. 9. Hemoglobin is composed of 4 subunits that are arranged in a particular symmetry, what is the arrangement of symmetry? A) A 2 B) B 2 C) C 2 D) C 4 E) D 2 F) Tetrahedral symmetry 10. An alcohol can react with an aldehyde to form a (an), which can react with another alcohol to form a (an). A) hemiketal, ketal B) hemiacetal, acetal C) lactam, acetal D) glycoside, glycotide E) lactone, lactam

3 11. A monosaccharide converts to its in aqueous solution without the need for catalyst. A) anomer B) epimer C) diastereomer D) sugar alcohol E) None of these. 12. The most important physiological role of Myoglobin is to facilitate A) diffusion of oxygen B) metabolism of oxygen C) binding of oxygen D) reduction of oxygen E) storage of oxygen F) transport of CO According to the Hill plot analysis of O 2 binding to hemoglobin, the fourth oxygen to bind hemoglobin exhibits an affinity for that is times greater than that of the first oxygen. A) 3 B) 10 C) 30 D) 50 E) 100 F) 300 G) Why does fetal hemoglobin have decreased affinity for BPG relative to adult hemoglobin? A) Decreased BPG binding causes the fetal hemoglobin to shift towards R state. B) Increased BPG binding to adult hemoglobin causes shift to the R state. C) Decreased BPG binding increases number of heme residues available for O 2 binding. D) Decreased BPG binding causes low O 2 affinity in fetal muscle tissue E) all of the above 15. Draw complete the Fischer projection for the sugar shown in its Fischer projection (D-talose). 16. is the fatty acids with the lowest expected melting point. A) palmitic (16:0) B) a-linoleic (18:3) C) stearic (18:0) D) linoleic (18:2) E) cis-oleic (18:1) 17. and are not reducing sugars. A) glucose, galactose B) trehalose, starch C) sucrose, trehalose D) starch, glycogen E) galactose, sucrose F) ribose, ribulose 18. Which of the following statements regarding K value in the equation for the oxygen binding curve of myoglobin is correct? A) Numerically it is equal to p 50. B) It is po 2 value at which Y = 0.5. C) It is a measure of oxygen binding affinity of myoglobin. D) It is partial pressure of oxygen at which half of the oxygen binding sites are occupied. E) All of the above 19. For muscular contraction to progress the energy stored in ATP is utilized by A) G-actin B) F-actin C) tropomyosin D) myosin tails E) myosin heads 20. Which statement about expression of actin is not correct? A) It is the most abundant protein in cytoplasm of many types of cells. B) It is expressed only in muscle cells. C) It is found in non-muscle cells. D) G-actin is expressed in non-muscle cells E) It is expressed in most types of cells. 21. Which statement characterizes uronic acids?

4 A) Aldoses where the aldehyde has been oxidized to a carboxylic acid. B) Aldoses where the primary alcohol has been oxidized to a carboxylic acid. C) Aldoses where the aldehyde is reduced to an alcohol. D) Aldoses where the primary alcohol has been oxidized to an aldehyde. 22. cannot be broken down by mammalian digestive enzymes. A) cellulose B) amylopectin C) amylose D) glycogen E) starch 23. Which one of these characteristics is true for the α helix? A) It is a coiled coil B) There are 3.5 amino acids per turn. C) There is a requirement for glycine every third amino acid residue. D) A hydrogen bond forms between the carbonyl oxygen of the nth amino acid residue and the NH group of the (n + 4)th amino acid residue. E) Prolines are often found within an α helix. 24. Characteristic properties of cholesterol include: A) disruption of membrane upon incorporation B) high water solubility C) fast breakdown with UV light. D) a precursor to steroid hormones. E) None of these 25. Without ascorbic acid you are unable to oxidize residues in collagen, resulting in scurvy. A) protamine B) glycine C) proline D) lysine E) hydroxylproline 26. Of those amino acids pairs listed below, the interaction of the side change with the side chain would have the least influence on protein stability. A) Arg, Glu B) Asp, Lys C) Lys, Glu D) Asp, Arg E) Leu, Ile 27. The following statement characterizes cellulose. A) linear polymer of glucose with β(1 4) linkages B) linear polymer of glucose with α(1 4) linkages C) linear polymer of galactose with β(1 4) linkages D) linear polymer of galactose with α(1 4) linkages 28. Which of these polysaccharides adopts a helical conformation? A) α-amylose B) chitin C) spiralulose D) lignin E) cellulose 29. Which of the following is a way that the low ph found in the gut can enhance the digestibility of dietary protein? A) disulfide reduction B) salt bridge formation C) cysteine oxidation D) protein structure denaturation E) amide hydrolysis F) carboxy-terminus protonation 30. When comparing similarities among multiple protein structures, which of the following is false? A) Proteins with similar motifs are likely to perform similar functions. B) An effective protein motif is likely to be observed in multiple proteins. C) Proteins with the same function from a different species are likely to have similar motifs. D) Proteins with similar sequences tend to adopt different backbone conformations E) None of the above statements are false. 31. is not a noncovalent interaction that stabilizes protein structure. A) salt bridges B) disulfide bridges C) electrostatic interactions with metal ions D) the hydrophobic effect E) hydrogen bonding F) All are.

5 32. Characteristics of unsaturated fatty acids include A) found in plants but rarely in animals B) usually contain a double bond with trans stereochemistry C) always contain multiple double bonds D) can be converted to fats with lower melting temperature by hydrogenation E) None of these. 33. Protein diseases can be caused by which of the following A) Activity of molecular chaperones. B) Formation of ion pairs during folding C) Mutations affecting the tertiary structure. D) All of the above are potential causes. E) None of the above are potential causes. 34. Protein dynamics is a field of study that examines the movements with in a protein. Which experimental method would be most useful to study this type of change? A) Electrospray Ionization mass spectrometry B) X-ray absorption spectroscopy C) X-ray crystallography D) Nuclear Magnetic Resonance E) None of the above 35. Which of the following is accomplished by molecular chaperones? A) They bind to misfolded proteins in order to protect against heat denaturation B) They facilitate aggregation of multiple subunits of a protein during synthesis C) They ensure that hydrophobic segments do not aggregate improperly D) They expose hydrophobic segments during protein synthesis, facilitating native folding E) None of the above are accomplished by molecular chaperones. 36. comprises bacterial cell walls. A) proteoglycans B) chondroitin sulfate chains C) peptidoglycans D) heparin E) pectin 1. Which of the following statements is true? A) Fatty acids with more than 18 carbons are the most common. B) Synthesis of fatty acids occurs in 2 carbon units. C) Fatty acids with conjugated double bonds very common in plants. D) In higher plants and animals, C 12 and C 14 species predominate. 37. The OH group of commonly attaches O-linked oligosaccharides. A) aspartic acid B) glycine C) lysine D) threonine E) tyrosine 38. Even though peptide groups assume the trans conformation most of the time, 10% of the time, peptide bonds involving assume the cis conformation because of altered steric hindrance. A) Proline B) Glycine C) Alanine D) Tryptophan E) None of the above 39. We use triglycerides for long-term storage of energy, rather than sugars, because triglycerides: A) Are more water soluble. B) More oxidized. C) Contain stronger covalent bonds. D) Serve also as materials for membranes. E) None of these. 40. Topology diagrams of proteins illustrate: A) The path taken by a protein through a cell B) The relative height of the protein surface C) The symmetry of subunits D) The connectivity of secondary structure elements

6 4 points each. 41. Draw cholesterol. 42. Draw Ascorbic acid (vitamin C). 43. Why do packages of Jell-O brand gelatin say that the product is not a complete source of protein? 44. Rigor mortis, the stiffening of muscles after death, is caused by depletion of ATP. Briefly describe the molecular basis of rigor. 45. Most hormones, such as peptide hormones, exert their effects by binding to cell-surface receptors. However, steroid hormones do so by binding to cytosolic receptors. How is this possible?