Chapter 44

Single-celled Paramecium live in pond water (a hyposmotic environment relative to the cytosol). They have a structural feature, a contractile vacuole, that enables them to osmoregulate. If sucrose or sodium chloride was added to the pond water, at which final concentration is the contractile vacuole likely to be most active?

0.0 mM sucrose

Which of the following statements best describes the actions of the hormone ADH on the nephron?

ADH causes the collecting duct to increase water reabsorption by the surrounding tissue under conditions of dehydration.

Which of the following describes how antidiuretic hormone (ADH) and the renin-angiotensin-aldosterone system (RAAS) work together to maintaining osmoregulatory homeostasis?

ADH regulates the osmolarity of the blood by altering renal reabsorption of water, and the RAAS maintains the osmolarity of the blood by stimulating both Na+ and water reabsorption.

Select the correct statement about osmoregulation

All osmoconformers are marine animals.

What is the driving force for the filtration of blood by the renal corpuscle?

Higher pressure in glomerular capillaries than in the surrounding Bowman's capsule.

Which answer best describes the formation of urea in mammals?

It forms in the liver from NH3 and carbon dioxide.

In which region of the nephron is a steep osmotic gradient created?

Loop of Henle.

Studies of cricket Malpighian tubules revealed that potassium ions accumulated inside the tubule, moving against the potassium concentration gradient. Based on the information, which of the following is the best inference about the mechanism of potassium transport?

Movement of potassium into the lumen of the Malpighian tubules is likely an energy-requiring process.

Select the correct statement about osmolarity.

Osmolarity measures the moles of solute per liter of solution.

Which of the following represents the correct sequence of flow through the nephron?

Renal corpuscle > proximal tubule > loop of Henle > distal tubule > collecting duct

Which regions of the nephron function independently of hormonal control for the most part?

Renal corpuscle, proximal tubule, and loop of Henle.

African lungfish, which are often found in small, stagnant pools of fresh water, produce urea as a nitrogenous waste. What is the advantage of this adaptation?

Small, stagnant pools do not provide enough water to dilute ammonia, which is toxic.

Which of the following statements is true?

The kidneys are paired organs that regulate water and electrolyte balance in terrestrial vertebrates.

What is the basic functional unit of the kidney?

The nephron.

Select the correct statement describing the osmolarity of mammalian urine.

The osmolarity of mammalian urine may vary over time.

Salmon eggs hatch in fresh water. The fish then migrate to the ocean (a hyperosmotic solution) and, after several years of feeding and growing, return to fresh water to breed. Which statement best explains how these organisms make the transition from fresh water to ocean water and back to fresh water?

The salt transport mechanisms of the gill epithelia change during migration.

Studies of cricket Malpighian tubules revealed that potassium ions move against the concentration gradient and accumulate inside the tubule. Which statement best predicts the effect of the potassium concentration gradient on the movement of water in the Malpighian tubules?

There will be a net movement of water into the lumen of the tubules.

Which of the following best describes the role of transport epithelia in osmoregulation of marine fish with bony skeletons?

They are involved in excretion of excess salt.

Which of the following is a general property of epithelial cells?

They display an apical and a basal surface that define cell polarity.

What is the difference between a countercurrent multiplier system, such as the one involving the loop of Henle, and the countercurrent systems that maximize oxygen absorption by fish gills or reduce heat loss in endotherms?

Unlike the other countercurrent systems, a countercurrent multiplier system, such as the one involving the loop of Henle, expends energy in active transport.

Part complete If you are hiking through the desert for several days, drinking which of the following would best ensure proper hydration?

a drink with a combination of water and electrolytes

In which of the following species should natural selection favor the highest proportion of juxtamedullary nephrons?

a mouse species living in a desert

Glucose is removed from filtrate by _____.

active transport

Which statement best describes the transfer of fluid from the glomerulus to Bowman's capsule?

blood pressure in the capillaries of the glomerulus causes transfer to occur

Antidiuretic hormone (ADH) makes the _____ permeable to water.

collecting duct

The structural component(s) of the mammalian nephron where increased permeability to water occurs due to the action of anti-diuretic hormone is⁄are the __________.

collecting duct

The loop of Henle dips into the renal cortex. Which statement best explains the advantage of this feature for osmoregulation in terrestrial vertebrates?

differential permeabilities of ascending and descending limbs of the loop of Henle are important in establishing an osmotic gradient

The high osmolarity of the renal medulla is maintained by which of the following?

diffusion of salt from the ascending limb of the loop of Henle.

Which of the following can trigger osmoregulatory adjustment via the atrial natriuretic peptide system?

drinking several glasses of water

Which of the following processes must freshwater fish undertake to maintain homeostasis?

excrete large quantities of water

Nitrogen is absent from

fatty acids.

The movement of substances out of the glomerulus and into Bowman's capsule is referred to as _____.

filtration

Which process in the nephron is least selective?

filtration

Which process does not display solute specificity?

filtration from the glomerular capillaries

Which option correctly associates the mechanism for osmoregulation or nitrogen removal with the appropriate animal?

flame bulb-flat worm

Excessive formation of uric acid crystals in humans leads to which of the following medical conditions?

gout, a painful inflammatory disease that primarily affects the joints

Consuming alcohol results in increased urine excretion due to which of the following?

inhibited secretion of antidiuretic hormone (ADH)

An appropriate group of animals to examine to observe a Malpighian tubule would be the __________.

insects

Aldosterone __________.

is a steroid hormone that reduces the amount of fluid excreted in the urine

Compared to the seawater around them, most marine invertebrates are ________.

isoosmotic

The body fluids of an osmoconformer would be ________ with its ________ environment.

isoosmotic; seawater

Which of the following best explains the death of a marine sea star that had been mistakenly placed in fresh water?

it was so hyperosmotic to the fresh water that it could not osmoregulate and thus its tissues swelled

An excretory system that is partly based on the filtration of fluid under high hydrostatic pressure is the ________.

kidneys of vertebrates

Which of the following is characteristic of juxtamedullary nephrons?

long loop of Henle

Which of the following best explains the death of a freshwater fish that had been placed accidentally in saltwater?

loss of water by osmosis from cells in vital organs resulted in cell death and organ failure

Which of the following occurs in processing of filtrate in the proximal and distal tubules?

maintenance of homeostasis of pH in body fluids

Which of the following animals generally has the lowest volume of urine production?

marine bony fish

Osmoregulation and excretion are __________.

mechanisms that maintain volume and composition of body fluids

As filtrate moves down the loop of Henle, the surrounding interstitial fluid becomes _____ concentrated than the filtrate, so _____ leaves the filtrate.

more ... water

Under the influence of antidiuretic hormone (ADH), _____ is produced.

more concentrated urine

Which of the following will likely occur in a human who has no access to fresh water but is forced to drink seawater instead?

passive excretion of excess water in feces in order to remove the high concentration of ingested salt

In animals, the catabolism of which molecules contributes most to the production of nitrogenous wastes?

proteins and nucleic acids

Materials are returned to the blood from the filtrate by which of the following processes?

reabsorption

Unlike an earthworm's metanephridia, a mammalian nephron

receives filtrate from blood instead of coelomic fluid.

The movement of substances from the blood into the proximal tubule is known as _____.

secretion

Which statement best describes the process of secretion?

selective elimination of excess ions and toxins from body fluids

The force driving simple diffusion is ________, while an energy source that drives active transport is ________.

the concentration gradient; ATP

Which statement best explains the relatively high metabolic rate of kidneys compared to the other body organs?

they operate an extensive set of ion pumps

Unlike most bony fishes, sharks maintain body fluids that are isoosmotic to seawater, so they are considered by many to be osmoconformers. Nonetheless, sharks osmoregulate at least partially by ________.

tolerating high urea concentrations that are balanced with internal salt concentrations to seawater osmolarity

Part complete The most abundant solute in urine is _____.

urea

Which of the following is an advantage of excreting nitrogenous wastes as urea rather than as ammonia?

urea is less toxic than ammonia

As a result of the non-selectivity of the mammalian kidney's filtration of small molecules, __________.

useful substances must be selectively reabsorbed