Exam_3_10am_key - BISC 220 Third hourly examination 8 April...

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BISC 220 Third hourly examination 8 April 2005 Please circle your TA's initials: SB AC MC XLiang XLiu JLui JLu CP HP KR JS YingW YuanYuan JW KC Name___________________________________ 10 AM EXAMINATION ID Number_____________________ This exam consists of NN questions on N pages. Be sure you have a complete copy. Please put your name and SID on the top of each page. For each of the following questions choose the one best answer. Write your answer in only the space provided—answers elsewhere will not be graded. The point value of each question is indicated. You have 50 minutes to complete this exam. Use your time wisely. Good luck from all your teaching staff. -1- Points on this page 1. (4 pts.) Which one of the following is not a function of the liver? (c) a. Converting glucose to glycogen immediately following a meal. b. Processing nutrients returning from the intestine via the hepatic portal vein. c. Synthesis of digestive enzymes to be secreted into the small intestine. d. Synthesis of plasma proteins. 2. (10 pts.) Pepsin is one of the few enzymes that works best in the highly acidic environment of the stomach contents. Digestive enzymes in the duodenum, however, require neutral or slightly alkaline levels of pH in order to function. Explain the mechanisms that allow duodenal enzymes to function even though the stomach continually releases its acidic contents into the duodenum. ANS: The release of acidic stomach contents into the duodenum stimulates the release of the hormone secretin from the duodenum. Secretin causes the pancreas to secrete an alkaline fluid, consisting of concentrated NaHCO 3 , into the pancreatic duct which empties into the duodenum. Thus, the stomach acid is neutralized and intestinal pH is raised to levels that permit digestive enzymes to work there. 3. (4 pts.) In which one of the following structures is average blood pressure the lowest? (d) a. aorta d. venae cavae b. venules e. arteries c. arterioles f. capillaries Answer in box Answer in box Answer in box
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Name___________________________________ -2- Points on this page 4. (10 pts.) In the glomeruli of the kidney, capillaries leak fluid into Bowman’s capsule. In contrast, nearby capillaries absorb water from the proximal tubule. Briefly explain the forces that cause fluid flow to be oppositely directed in these two locations. ANS: In the glomerulus, the outwardly directed blood pressure force is greater than the inwardly directed force due to the osmotic (oncotic) pressure of plasma proteins. Thus, the net force is outward and fluid leaks. The tubular capillaries surrounding the distal tubule are downstream from the glomerulus, so blood pressure is less. In addition, the retention of protein in the blood increases the osmotic pressure. The inwardly directed osmotic pressure exceeds the blood pressure, so the net force is inward and the capillaries absorb water. 5. (10 pts.) Briefly explain why exercise tends to lower the pH of the blood, and how the
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This note was uploaded on 05/03/2010 for the course BISC 220L taught by Professor Herrera,mcclure during the Spring '07 term at USC.

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Exam_3_10am_key - BISC 220 Third hourly examination 8 April...

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