P215 Basic Human Physiology Summer 2003 Lab Exam #1

Transcription

1 PLEASE BE AWARE CONTENT COVERED ON EXAMS VARIES FROM ONE SEMESTER TO ANOTHER. THIS EXAM MAY NOT CONTAIN MATERIAL THAT WILL BE ON YOUR EXAM THIS SEMESTER, AND/OR MAY CONTAIN MATERIAL THAT WILL NOT BE COVERED ON YOUR EXAM. P215 Basic Human Physiology Summer 2003 Lab Exam #1 Name I recommend answering the question on the exam itself first, then marking your answer sheet at the end once you have decided on an answer. Do not erase an answer from the answer sheet Either/Or Questions. (2 points each, 14 points total) Choose the answer that makes the statement true. 1. Molecules that are (a. polar / b. nonpolar) have difficulty passing through a lipid bilayer. 2. A cell placed in a hypotonic solution will (a. shrink / b. swell). 3. (a. Saturated / b. Unsaturated) fatty acids have all their carbons linked together by single covalent bonds. 4. According to Beer s law, the concentration of a solution is directly proportional to the (a. absorbance / b. transmittance) of the solution. 5. The (a. atomic number / b. atomic weight) of an element is the average number of protons and neutrons in an atom of that element. 6. As a group, lipids tend to be (a. hydrophilic / b. hydrophobic). 7. Enzymes (a. can / b. cannot) provide the energy necessary to drive energetically unfavorable reactions. Multiple Choice Questions. (3 points each, 36 points total) Choose the BEST answer and mark the appropriate letter on your answer sheet. 8. A solution of ph 8 has the concentration of hydrogen ions as does a ph 9 solution. a) 8/9 th c) 10 times b) 9/8 th d) 1/10 th 9. are formed when two atoms share valence electrons unequally. a) Ionic bonds c) Nonpolar covalent bonds b) Hydrogen bonds d) Polar covalent bonds 10. Carbon (atomic number = 6), has valence electrons. a) 0 c) 4 b) 2 d) 6

2 11. Calculate the number of moles present in 90 g of acetic acid (MW = 60 g/mole) a) 5400 moles c) 1.5 moles b) 30 moles d) 0.67 moles g of glycine (MW = 75 g/mole) are mixed with water enough water to produce 1 L of solution. What is the molarity of this solution? a) 2 M c) M b) 0.5 M d) 37.5 M 13. If the hydrogen ion concentration [H + ] of a water-based solution is M, the solution would be a) neutral c) acidic b) alkaline d) stinky 14. Complex biomolecules are broken into their individual building blocks through a) hydrolysis reactions c) condensation reactions b) dehydration synthesis d) didactic synthesis 15. The structure of a protein is the sequence of amino acids within a polypeptide chain. a) quaternary c) secondary b) tertiary d) primary 16. are positively charged atoms or molecules. a) cations c) isomers b) anions d) isotopes 17. refers to the relative difference in osmotic pressure between two solutions, and indicates the net movement of water during osmosis. a) molarity c) osmolality b) molality d) tonicity 18. What is the osmolality of a solution consisting of 1 mole NaCl mixed in 500 ml of water (Note: NaCl dissociates into Na + + Cl - when dissolved in water)? a) 0.25 Osm c) 1 Osm b) 4 Osm d) 2 Osm

3 19. Which of the following illustrations best demonstrates the relationship between the rate of an enzyme-catalyzed reaction and enzyme concentration? a) b) c) d) Short answer questions: 1. Explain why rates of enzyme-catalyzed reactions increase with temperature to an extent, but then decrease again at very high temperatures (5 points) 2. PART A). You mix together a glucose solution consisting of 360 g of glucose (MW = 180 g/mole) mixed with 2 L of water. What is the molality of this solution? (4 points) PART B). You find a bottle labeled glucose solution on the shelf in the lab, but there is no indication as to what the concentration of that solution is. You react a sample of it and a sample of the solution you just mixed above with a colorimetric reagent, and measure absorbance with a spectrophotometer. The solution you prepared in Part A above (the standard ) has an absorbance of 0.400, whereas the solution you found on the shelf (the unknown ) has an absorbance of Based upon the concentration of the standard you calculated in Part A and your knowledge of Beer s Law, determine the concentration of the unknown solution. (4 points)

4 3. Creatine kinase (CK) is an enzyme that catalyzes the transfer of phosphate groups from creatine phosphate to ADP to form ATP. This provides a quick means of regenerating ATP in active tissues, such as skeletal muscle. Elevated levels of CK in blood plasma are associated with disorders such as muscular dystrophy, pulmonary infarction, cerebrovascular disease, hypothyroidism, and myocardial infarction. You are a lab technician working for the U.S. government in a top-secret facility in an undisclosed location. Richard B. Cheney, Vice President of the United States and probable corporate wrongdoer, comes into the infirmary complaining of chest pains. Believing that heart attack #5 may be in progress, the attending physician orders a suite of tests, including one for CK levels. Using a set of CK standards, you generate a standard curve to predict enzyme activity using change in absorbance per minute. 1) If the change in absorbance per minute is 0.5, estimate the CK activity Mr. Cheney s blood plasma using the standard curve. (4 points) 2) If normal values for CK are U/L in males, does Mr. Cheney have the elevated CK levels that might be associated with myocardial infarction? (2 points) 4. Describe the difference between molarity and molality (6 points total)

5 Answer Key Problem Answer Problem Answer 1 A 11 C 2 B 12 B 3 A 13 B 4 A 14 A 5 B 15 D 6 B 16 A 7 B 17 D 8 C 18 B 9 D 19 A 10 C Short Answer Questions 1. Reaction rates typically increase with increasing temperature, since the frequency by which reactants collide together with enough energy for the reaction to occur increases. However, the shape of proteins is also influenced by temperature, as high temperatures tend to destabilize the weak noncovalent bonds that give a protein a particular tertiary or quaternary structure. Since the ability of the enzyme depends on having the proper 3-D arrangements of amino acid sidechains in its active site, alterations of the shape of the enzyme with increased temperature (i.e., heat denaturization) tends to decrease the ability of the enzyme to catalyze the reaction, and hence lowers the rate at which the reaction proceeds. 2. a) 1 molal, b) 0.75 molal 3. a) 100 U/L, b) this is in the normal range for adult males, so it is not indicative of a heart attack. 4. Briefly, molarity is the number of solute particles per unit volume of solution, whereas molality is the ratio of solute particles per solvent mass used to make the solution.