Patho/Phys Fall 2022

Patho/Phys Fall 2022 An artificial membrane is created consisting of a lipid bilayer without protein molecules in the membrane. The lipid composition of the membrane is essentially the same as that of a normal, biological membrane. Which of the following substances permeates the membrane more readily than water molecules? A. Carbon Dioxide B. Glucose C. Glycerol D. Sodium E. Urea ANS: A 2. A cell is equilibrated in an aqueous solution of 300 mOsm/L sodium chloride. Which of the following best describes what will happen to cell volume when the cell is placed in an aqueous solution of 300 mOsm/L calcium chloride? A. Decrease B. Decrease and then increase C. Increase D. Increase and then decrease E. No change ANS: E 3. The intracellular calcium ion concentration of ventricular muscle cells averages 10-4 mmol/L during diastole. The calcium ion concentration in transverse tubules (T-tubules) averages 2.5 mmol/L at rest. A protein transporter on the membrane of the T-tubule exchanges sodium for calcium. The transporter uses the transmembrane sodium gradient to fuel the exchange. Which of the following transport mechanisms best describes this type of transporter? A. Facilitated diffusion B. Primary active transport C. Secondary active co-transport D. Secondary active counter-transport E. Simple diffusion ANS: D 4. Human red blood cells (RBCs) and rabbit RBCs are equilibrated in separate solutions of isotonic saline (300 mOsm/L NaCl). The human RBCs are then placed in a solution of 300 mOsm/L glycerol, which causes them to swell and burst. However, rabbit RBCs placed in 300 mOsm/L glycerol neither swell nor shrink. Based on this information, which of the following can be concluded about a 300 mOsm/L solution of glycerol for the different cell types? Human RBCs A. Hypertonic and hyperosmotic B. Hypotonic and hypoosmotic C. Hypotonic and isoosmotic D. Isotonic and hypoosmotic E. Isotonic and isoosmotic F. Isotonic and hyperosmotic Rabbit RBCs A. Hypotonic and hypoosmotic B. Hypertonic and hyperosmotic C. Isotonic and isoosmotic D. Isotonic and hyperosmotic E. Hypotonic and isoosmotic F. Isotonic and isoosmotic ANS: C 5. The molarity of a 2% solution of NaCl is 340 mmol/L. The molecular weight of NaCl is 58.5. What is the osmolarity of a 2% solution of NaCl (in mOsm/L)? A. 170 B. 340 C. 510 D. 680 ANS: D 6. Secondary active transport typically moves which of the following substances against a concentration gradient? Glucose. Amino acids Sodium ions A. NO. NO. NO B. NO. NO. YES C. YES. NO. YES D. YES. YES. NO E. YES. YES. YES ANS: D . Which of the following transport mechanisms can move sodium ions across a cell membrane? Primary active | Secondary active | Simple diffusion A. NO. NO NO B. NO YES YES C. YES NO YES D. YES YES NO E. YES YES YES ANS: E The diagram illustrates possible changes in red blood cell volume resulting from a change in extracellular fluid composition for a cell equilibrated in a 150 mmol/L solution of sodium chloride (NaCl) at time zero. Which curve best illustrates the volume change caused by immersion of the cell in an aqueous solution of 300 mOsm/L calcium chloride (CaCl2)? ANS: C The cell membrane is leastpermeable to which of the following substances? a. Sodium b. Oxygen c. Ethanol d. Carbon dioxide e. Water Sodium Exchange of substances between the cardiovascular system and the interstitial fluid occurs mainly in which of the following? a. Arteries b. Arterioles c. Capillaries d. Venules e. Veins Capillaries A pure phospholipid bilayer is most permeable to which of the following? a. Sodium b. Calcium c. Chloride d. Water e. Oxygen Oxygen Which of the following substances in most likely to represent the highest percent of cell mass in a typical cell of the body? a. Carbohydrates b. Ions c. Lipids d. Proteins e. Water Water The diagram shows a model cell that transports substance X across the cell membrane. The cell is equipped with a Na-K-ATPase pump as shown. Substance X enters the cell by a coupled transport mechanism and exits the cell by carrier-mediated diffusion. Treatment with a substance that inhibits the Na-K-ATPase pump inhibits the transport of X by which of the following mechanisms? A. Decreasing intracellular K+ concentration B. Decreasing intracellular Na+ concentration C. Increasing intracellular K+ concentration D. Increasing intracellular Na+ concentration ANS: D A 42-year-old woman decides to lose weight on a diet prescribed by an anorexic friend. She loses about 30 pounds in 45 days, but her serum potassium level falls to 2.1 mmol/L (normal: 3.5 to 5.0 mmol/L). Which of the following changes is most likely to occur in this young woman? A. Depolarization of the resting membrane potential B. Hyperpolarization of the resting membrane potential C. Increased intracellular potassium concentration D. Potassium equilibrium potential becomes less negative ANS: B 3. An 22-year-old man is admitted to the emergency department after an automobile accident. He has not lost a large amount of blood, but he suffers from a severe crush injury to his right leg. He is conscious and exhibits flaccid paralysis. Electrocardiogram results show a shortened QT interval and an increase in the P-R interval (i.e., decreased duration of action potential and decreased conduction velocity). Laboratory results indicate that his serum potassium level has increased to a value of 6.5 mEq/L (normal: 3.5 to 5.0 mEq/L). This increase in serum potassium causes which of the following? A. A decreased net driving force for potassium from cells B. Decreased intracellular potassium concentration C. Hyperpolarization of the resting membrane potential D. More negative Nernst potential for potassium E. More negative resting membrane potential ANS: A An 88-year-old nursing home resident has diabetes mellitus and is taking diuretics for hypertension. His blood glucose concentration has recently been greater than 350 mg/dL. He is disoriented and has had limited oral intake for about five days. His vital signs include a temperature of 100.5°F, a supine blood pressure and pulse of 150/90 mm Hg and 100 beats per minute, and an upright blood pressure and pulse of 130/88 mm Hg and 118 beats per minute. The findings on examination of the heart are normal, and his axillae are dry. The table shows serum Na+ and K+ values before and after the dehydration that has occurred in this patient. The resting membrane potential of a cardiac myocyte was about −70 millivolts before dehydration occurred. What is the resting membrane potential of a cardiac myocyte after dehydration occurred, assuming no change in membrane conductance or intracellular concentrations of Na+ or K+ ions? A. −100 millivolts B. −50 millivolts C. −60 millivolts D. −70 millivolts E. −90 millivolts ANS: D A 56-year-old woman is referred to the neurology clinic for evaluation of her long- term problem of a stumbling gait and a tendency to fall. Her visual acuity also seems to change periodically. Neurological findings suggest multiple sclerosis. This diagnosis is further supported by magnetic resonance imaging, which shows of areas of demyelination in the central nervous system. Other tests show the presence of oligoclonal bands in the spinal fluid. The loss of myelin from a nerve fiber has which of the following effects? A. Decreased conduction velocity of action potential or no action potential B. Decreased energy requirement for successful action potentials C.Increased conduction velocity of action potential