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44 .

A diagram shows a patient’s arm, with an arrow representing blood leading from the arm to a dialyzer. In the dialyzer, the waste in the blood is drawn through a semipermeable membrane toward a compartment filled with fresh dialysate. The used dialysate then flows to a collecting bottle. The clean blood is returned to the patient’s same arm.

Patients with kidney illnesses use dialysis machines to remove harmful urea from their blood. The blood is separated from a solution, called the dialysate, that is designed to remove wastes by diffusion through a semipermeable membrane. How does the concentration of solutes likely differ between the upper component of the dialyzer and the lower compartment, containing the fresh dialysate, for the dialysis to successfully remove wastes from the blood?

  1. In the upper component, the dialysate has a higher solute concentration than the blood, which allows the urea to diffuse to the lower dialysate down its concentration gradient.
  2. In the upper component, the dialysate has a lower solute concentration than the blood, which allows the urea to be separated via active transport down the concentration gradient.
  3. In the upper component, the dialysate has a higher solute concentration than the blood, which allows the urea to utilize facilitated diffusion in order to diffuse to the lower dialysate.
  4. In the upper component, the dialysate has a lower solute concentration than the blood, which allows the urea to diffuse to the lower dialysate down its concentration gradient.
45 .

Solution A contains shriveled red blood cells. Solution B contains bloated red blood cells. One of the bloated cells has burst.

The diagram shows red blood cells in two different NaCl solutions. What is likely causing the cells to differ in shape in the two solutions?

  1. Solution A has high osmolarity. Solution B has low osmolarity.
  2. Solution A has low osmolarity. Solution B high osmolarity.
  3. The cells in solution A are osmoregulators. The cells in solution B are osmoconformers.
  4. The cells in solution A are osmoconformers. The cells in solution B are osmoregulators.
46 .

Illustration shows a fish in an environment where water is absorbed through the skin. The fish drinks little water and excretes dilute urine. Sodium, potassium, and chlorine ions are lost through the skin, and the fish actively transports these same ions into its gills to compensate for this loss.

This diagram models the osmotic pressures experienced by a fish. Based on the direction of water and solute movements shown in the diagram, is this fish likely a saltwater or freshwater fish? How do you know?

  1. freshwater, because the fish is osmoregulating in response to a hypertonic solution
  2. freshwater, because the fish is osmoregulating in response to a hypotonic solution
  3. saltwater, because the fish is osmoregulating in response to a hypertonic solution
  4. saltwater, because the fish is osmoregulating in response to a hypotonic solution
47 .

Illustration shows a fish in an environment where water is absorbed through the skin. The fish drinks little water and excretes dilute urine. Sodium, potassium, and chlorine ions are lost through the skin, and the fish actively transports these same ions into its gills to compensate for this loss.

The diagram models the osmotic pressures experienced by a fish.

Which option is a claim that can be written based on this diagram?

  1. The fish lives in saltwater with high osmolarity. This causes accumulation of salts in the body of the fish.
  2. The fish lives in freshwater with low osmolarity. This causes water to constantly diffuse into the fish’s body.
  3. The fish lives in saltwater with high osmolarity. This causes water to constantly diffuse into the fish’s body.
  4. The fish lives in freshwater with low osmolarity. This causes accumulation of salts in the body of the fish.
48 .

A diagram shows a patient’s arm, with an arrow representing blood leading from the arm to a dialyzer. In the dialyzer, the waste in the blood is drawn through a semipermeable membrane toward a compartment filled with fresh dialysate. The used dialysate then flows to a collecting bottle. The clean blood is returned to the patient’s same arm.

Patients with kidney illnesses use dialysis machines to remove harmful urea from their blood. The blood is separated from a solution, called the dialysate, that is designed to remove wastes by diffusion through a semipermeable membrane. The semipermeable membrane is likely permeable to _____ and impermeable to _____.

  1. red blood cells, urea
  2. dialysate, blood plasma
  3. blood plasma, urea
  4. urea, red blood cells
49 .

A U-shaped tube represents the loop of Henle. The filtrate enters the descending limb and exits the ascending limb. The descending limb is water-permeable, and water travels from the limb to the interstitial space. As a consequence, the osmolality of the filtrate inside the limb increases from 300 milliosmoles per liter at the top to 1200 milliosmoles per liter at the bottom. The ascending limb is permeable to sodium and chloride ions. Because the osmolality inside the bottom part of the limb is higher than the interstitial fluid, these ions diffuse out of the ascending limb. Higher up, sodium is actively transported out of the limb, and chloride follows.

The diagram models the countercurrent exchange mechanism within the loop of Henle. The numbers within the loop show the osmolarity of the filtrate, while the numbers between the two loops indicate the osmolarity of the interstitial fluid within the kidney tissue. What would likely occur to the osmolarity of the filtrate in the ascending limb if the active transport of NaCl stopped?

  1. Filtrate osmolarity would increase, then decrease.
  2. Filtrate osmolarity would stay the same.
  3. Filtrate osmolarity would decrease.
  4. Filtrate osmolarity would increase.
50 .

A U-shaped tube represents the loop of Henle. The filtrate enters the descending limb and exits the ascending limb. The descending limb is water-permeable, and water travels from the limb to the interstitial space. As a consequence, the osmolality of the filtrate inside the limb increases from 300 milliosmoles per liter at the top to 1200 milliosmoles per liter at the bottom. The ascending limb is permeable to sodium and chloride ions. Because the osmolality inside the bottom part of the limb is higher than the interstitial fluid, these ions diffuse out of the ascending limb. Higher up, sodium is actively transported out of the limb, and chloride follows.

The diagram models the countercurrent exchange mechanism within the loop of Henle. The numbers within the loop show the osmolarity of the filtrate, while the numbers between the two loops indicate the osmolarity of the interstitial fluid within the kidney tissue. What would happen to the osmolarity of the interstitial fluid if water could not exit the descending limb?

  1. Osmolarity of the interstitial fluid would increase.
  2. Osmolarity of the interstitial fluid would decrease.
  3. There would be no change in the osmolarity.
  4. Osmolarity would increase or decrease depending upon the amount of water.
51 .

A labeled illustration shows the kidney, shaped like a kidney bean standing on end. Two layers, the outer renal fascia and an inner capsule, cover the outside of the kidney. The inside of the kidney consists of three layers: the outer cortex, the middle medulla, and the inner renal pelvis. The renal pelvis is flush with the concave side of the kidney and empties into the ureter, a tube that runs down outside the concave side of the kidney. Nine renal pyramids are embedded in the medulla, which is the thickest kidney layer. Each renal pyramid is teardrop-shaped, with the narrow end facing the renal pelvis. The renal artery and renal vein enter the concave part of the kidney, just above the ureter. The renal artery and renal vein branch into arterioles and venules, respectively, which extend into the kidney and branch into capillaries in the cortex.

The diagram shows a cross-section of a kidney. What would likely occur if there was a blood clot in the renal artery?

  1. Filtration in the glomerulus would decrease.
  2. Fluid levels in the renal pelvis would increase.
  3. Blood would not drain into the convoluted tubule.
  4. Urea production would increase.
52 .

An illustration without labels shows the kidney, shaped like a kidney bean standing on end. Two layers, the outer renal fascia and an inner capsule, cover the outside of the kidney. The inside of the kidney consists of three layers: the outer cortex, the middle medulla, and the inner renal pelvis. The renal pelvis is flush with the concave side of the kidney and empties into the ureter, a tube that runs down outside the concave side of the kidney. Nine renal pyramids are embedded in the medulla, which is the thickest kidney layer. Each renal pyramid is teardrop-shaped, with the narrow end facing the renal pelvis. The renal artery and renal vein enter the concave part of the kidney, just above the ureter. The renal artery and renal vein branch into arterioles and venules, respectively, which extend into the kidney and branch into capillaries in the cortex.

The diagram shows the left kidney. Why do the capillaries carrying blood from the renal artery run over the top of the renal pyramids?

  1. The capillaries deliver blood to the glomerulus and run parallel to the proximal convoluted tubule. Both are located in the medulla.
  2. The capillaries deliver blood to the glomerulus and run perpendicular to the proximal convoluted tubule. Both are located in the cortex.
  3. The capillaries deliver blood to the glomerulus and run perpendicular to the distal convoluted tubule. Both are located in the cortex.
  4. The capillaries deliver blood to the glomerulus and run parallel to the distal convoluted tubule. Both are located in the cortex.
53 .

Illustration labels parts of a nephron. The nephron begins at the glomerulus, a spherical structure. The filtrate enters a winding proximal convoluted tubule. The proximal convoluted tubule empties into the descending loop of Henle. The descending loop of Henle turns into the ascending loop of Henle. Both the descending loop and ascending loop are thin at the bottom, then turn thick about a third of the way up. The ascending loop of Henle empties into the distal convoluted tubule. The distal convoluted tubule empties into a collecting duct, which then travels down toward the middle of the kidney.

The figure shows the components of a nephron located within the kidneys. What would likely occur in the collecting duct if there was increased blood flow to the glomerulus?

  1. More water would enter the collecting duct.
  2. More urea would enter the collecting duct.
  3. Less NaCl would leave the collecting duct.
  4. Less urea would leave the collecting duct.
54 .

Illustration labels parts of a nephron. The nephron begins at the glomerulus, a spherical structure. The filtrate enters a winding proximal convoluted tubule. The proximal convoluted tubule empties into the descending loop of Henle. The descending loop of Henle turns into the ascending loop of Henle. Both the descending loop and ascending loop are thin at the bottom, then turn thick about a third of the way up. The ascending loop of Henle empties into the distal convoluted tubule. The distal convoluted tubule empties into a collecting duct, which then travels down toward the middle of the kidney.

The figure shows the components of a nephron located within the kidneys. Alcohol impairs the pituitary gland, which controls how much water is reabsorbed by the nephrons. The hormone produced by the pituitary gland, anti-diuretic hormone, increases water reabsorption by the kidney. How would impairment of this hormone likely affect the various components of the nephron pictured?

  1. Absorption of water from the filtrate would decrease, indicated by decreased loss of water in the descending loop of Henle, increased solute secretion into the distal tubule, and decreased water absorbtion in the collecting duct.
  2. Absorption of water from the filtrate would decrease, indicated by decreased loss of water in the ascending loop of Henle, increased solute secretion into the distal tubule, and increased water absorption in the collecting duct.
  3. Absorption of water from the filtrate would decrease, indicated by decreased loss of water in the ascending loop of Henle, increased solute secretion into the distal tubule, and decreased water absorbtion in the collecting duct.
  4. Absorption of water from the filtrate would decrease, indicated by decreased loss of water in the descending loop of Henle, increased solute secretion into the distal tubule, and increased water absorption in the collecting duct.
55 .

A U-shaped tube represents the loop of Henle. The filtrate enters the descending limb and exits the ascending limb. The descending limb is water-permeable, and water travels from the limb to the interstitial space. As a consequence, the osmolality of the filtrate inside the limb increases from 300 milliosmoles per liter at the top to 1200 milliosmoles per liter at the bottom. The ascending limb is permeable to sodium and chloride ions. Because the osmolality inside the bottom part of the limb is higher than the interstitial fluid, these ions diffuse out of the ascending limb. Higher up, sodium is actively transported out of the limb, and chloride follows.

The diagram models the countercurrent exchange mechanism within the loop of Henle. The numbers within the loop show the osmolarity of the filtrate, while the numbers between the two loops indicate the osmolarity of the interstitial fluid within the kidney tissue. What would likely happen to the osmolarity of the filtrate in the ascending limb if the body released urea into the interstitial fluid?

  1. The osmolarity would decrease, allowing the interstitial fluid to reabsorb solutes.
  2. The osmolarity would decrease, allowing the interstitial fluid to reabsorb water.
  3. The osmolarity would increase, allowing the interstitial fluid to reabsorb solutes.
  4. The osmolarity would increase, allowing the interstitial fluid to reabsorb water.
56 .

Illustration shows a flame cell, which is bulb-shaped with cilia projecting from one end. The cilia form a point, like the tip of a paintbrush, inside as wide opening at the end of a tube cell. The tube cell narrows into a tubule, then widens into a body where the nucleus is located. The tubule continues past the cell body.

"Planaria are flatworms that live in freshwater. Their excretory system consists of two tubules connected to a highly branched tube system. The intake end of the tubes contain cilia that propel waste matter down the tubules and out of the body through excretory pores that open on the body surface. Cilia also draw water from the interstitial fluid, allowing for filtration. Any valuable metabolites are recovered by reabsorption.

If we are building a model that compares the planarian and human excretory systems, what would be functionally analogous to the cilia described here?

  1. The renal artery, because it facilitates the exchange of nutrients with the blood.
  2. The convoluted tubule, because it facilitates the exchange of nutrients with the blood.
  3. The glomerulus, because it facilitates filtering of the blood.
  4. The ureter, because it facilitates filtering of the blood.
57 .

Illustration shows a flame cell, which is bulb-shaped with cilia projecting from one end. The cilia form a point, like the tip of a paintbrush, inside as wide opening at the end of a tube cell. The tube cell narrows into a tubule, then widens into a body where the nucleus is located. The tubule continues past the cell body.

Planaria are flatworms that live in freshwater. Their excretory system consists of two tubules connected to a highly branched tube system. The intake end of the tubes contain cilia that propel waste matter down the tubules and out of the body through excretory pores that open on the body surface. Cilia also draw water from the interstitial fluid, allowing for filtration. Any valuable metabolites are recovered by reabsorption.

If we are building a model that compares the planarian and human excretory systems, what would be functionally analogous to the highly branched tube system described here?

  1. The renal artery, because it facilitates the exchange of nutrients with the blood.
  2. The convoluted tubule, because it facilitates the exchange of nutrients with the blood.
  3. The glomerulus, because it facilitates filtering of the blood.
  4. The ureter, because it facilitates filtering of the blood.
58 .
Planaria are flatworms that live in fresh water. Their excretory system, or protonephridia, consists of two tubules connected to a highly branched tube system. The intake end of the tubes contain cilia that propel waste matter down the tubules and out of the body through excretory pores that open on the body surface. Cilia also draw water from the interstitial fluid, allowing for filtration. Any valuable metabolites are recovered by reabsorption. What structure in the human kidneys most closely resembles the excretory pores of the protonephridia, and why?
  1. The urethral opening, because this is where wastes leave the body
  2. The convoluted tubule, because this is where reabsorption and secretion occur
  3. The glomerulus, because this is where reabsorption and secretion occur
  4. The ureter, because this is where wastes leave the body.
59 .
The Malpighian tubules filter waste materials out of the blood, or hemolymph, of insects. There are cells lining the tubules that pump solutes (mainly ions) into the space surrounding the Malpighian tubules. If you observed a gradual increase in the solute concentration outside of the Malpighian tubules, what would you expect to happen?
  1. Water would be drawn out of the hemolymph within the tubule.
  2. Water would be drawn into the tubule.
  3. Ions would be drawn out of the hemolymph within the tubule.
  4. Ions would be drawn into the tubule.
60 .
The flame cells of a protonephridia filter waste materials out of the blood, or hemolymph, of invertebrates. What would this be most similar to, in function, in the human excretory system?
  1. the ascending loop of henle
  2. the descending loop of henle
  3. the distal convoluted tubule
  4. Bowman's capsule
61 .
Terrestrial arthropods, birds, and reptiles convert toxic ammonia to uric acid or the closely related compound guanine (guano). However, the conversion of ammonia to uric acid requires more energy and is much more complex than the conversion of ammonia to urea, or the excretion of ammonia as performed by fish. Based on these findings, how may the excretory system of one of the terrestrial organisms listed above change if it evolved to spend most of its time in water?
  1. They may evolve the ability to switch between uric acid and direct ammonia excretion.
  2. They would further reduce their excretion of ammonia.
  3. They may evolve the ability to excrete uric acid without having to dissolve it in any water.
  4. They would excrete higher concentrations of uric acid.
62 .

Birds and reptiles convert toxic ammonia to uric acid or a similar compounds. Insects, who live on land, also convert ammonia to uric acid. This is as opposed to fish, which excrete ammonia directly, without converting it to another substance.

The conversion of ammonia to uric acid requires energy and is more complex than excreting ammonia directly.

Based on this information, make a logical claim why these organisms could have evolved the conversion of ammonia to uric acid?

  1. To have the ability to switch between uric acid and ammonia excretion.
  2. To conserve water where water is in shorter supply.
  3. To reduce the impact in their environment because ammonia is harmful than uric acid.
  4. For living in symbiosis with plants, to which uric acid is important.
63 .
(credit: modification of work by Caravaggi, A. M. et al/Circulation Research)

This graph shows the renin and angiotensin II concentrations in blood.

What is a claim that can be done from this data? (Hint: Evaluate only the information shown in the graphs.)

  1. Renin and angiotensin II concentrations are not related to each other.
  2. Renin and angiotensin II concentrations are related to each other.
  3. Renin production is triggered by angiotensin II.
  4. Angiotensin II production is triggered by renin.
64 .
(credit: modification of work by Gary A. Rosenberg and Edward Y. Estrada/AHA Journals, under CC BY4.0 license)

The atrial natriuretic peptide (ANP) opens blood vessels. ANP also prevents sodium reabsorption by the renal tubules, decreasing water reabsorption. A research study explored if ANP reduced brain edema (excessive collection of water) in the brain in rats. The graph summarizes their findings. Each column is a different location in the rat brain.

Make a claim about ANP based on this graph.

  1. ANP reduces brain edema in rats.
  2. ANP causes brain edema in rats.
  3. ANP has no effect on brain edema in rats.
  4. ANP increases brain edema in some locations of the brain, and decreases it in other locations, in rats.
65 .

A flow diagram begins with angiotensin. Renin converts angiotensin into ACE. The enzyme angiotensin 1 converts ACE into angiotensin 2, which triggers the release of other hormones. Angiotensin 2 triggers the release of aldosterone and ADH.

This diagram was made by a student to illustrate the angiotensin-aldosterone system. What part of this diagram contains an error?

  1. ADH is not produced in this system.
  2. The diagram is missing ANP.
  3. ACE and renin should be switched.
  4. ACE and angiotensin should be switched.
66 .

An incomplete flow diagram begins with angiotensin. Renin is next to an arrow indicating it is involved in the next step, but the rest of the steps are missing.

This diagram was made by a student to illustrate the angiotensin-aldosterone system. How would you complete this diagram to make it an accurate model of the renin-angiotensin system?

  1. Renin acts on angiotensin to directly stimulate the release of aldosterone and ADH.
  2. Renin acts on angiotensin to form ACE and angiotensin II, which then stimulates the release of aldosterone and ADH.
  3. Angiotensin II is formed from angiotensin, which is then converted to angiotensin I by ACE. Aldosterone and ADH are then stimulated to be released from angiotensin I.
  4. Angiotensin I is formed from angiotensin, which is then converted to angiotensin II by ACE. Aldosterone and ADH are then stimulated to be released from angiotensin II.
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