Question 1

Which of the following affects the osmolarity of a solution?

Accepted Answer

Osmolarity is determined by the concentration of solutes in a solution, including glucose, salt, and the relative concentration of water.

Question 2

Which of the following most accurately describes selective permeability?

Accepted Answer

Selective permeability refers to the ability of a membrane to regulate what molecules can pass through it. This is achieved through the presence of transport and channel proteins in the membrane that selectively allow certain molecules to cross. Lipid-soluble molecules (choice B) are more likely to diffuse across the membrane, but this is not the only factor that determines selective permeability. Similarly, while concentration gradients (choice C) are important for determining the direction of molecular movement, they are not the only factor that determines whether molecules can cross the membrane. The idea that small molecules can cross the membrane easily (choice A) is also an oversimplification, since some small molecules may still require transport or channel proteins to cross the membrane.

Question 3

Sharks live in seawater.Their tissues are isotonic to seawater,but their concentrations of sodium ions,potassium ions,and chloride ions in cells and extracellular fluids are similar to those of freshwater fishes.How is that possible?

Accepted Answer

Sharks have additional compounds in their tissues that contribute to osmolarity, which enables them to maintain similar concentrations of sodium, potassium, and chloride ions as freshwater fish despite living in a hypertonic environment. Some of these compounds include urea, trimethylamine oxide, and glycerol.

Question 4

Which of the following are soluble compounds that contribute to intracellular osmolarity in shark tissues?

Accepted Answer

Sharks are osmoregulators that must maintain high solute concentrations in their tissues to counteract the influx of water. Urea and trimethylamine oxide (TMAO) are two solutes that contribute significantly to the shark's intracellular osmolarity. These compounds are highly soluble in water and can accumulate to very high concentrations within the shark's cells. In contrast, sodium and chloride ions are typically kept at much lower concentrations, as excessive levels of these ions can be toxic to cells. Glucose and amino acids can also contribute to intracellular osmolarity, but they are not as important as urea and TMAO in shark tissues. Proton pumps, although important for regulating pH, do not contribute to osmolarity in the same way as solutes such as urea and TMAO.

Question 5

What role do chloride cells play in osmoregulation of marine fish with bony skeletons?

Accepted Answer

The answer of What role do chloride cells play in...

Question 6

Marine vertebrates live in a(n)________ environment.

Accepted Answer

The answer of Marine vertebrates live in a(n)________ environment.
...

Question 7

Tissues of sharks are isotonic to seawater,but their concentrations of sodium ions,potassium ions,and chloride ions in cells and extracellular fluids are similar to those of freshwater fishes.What can you infer about the movement of sodium and chloride in these animals?

Accepted Answer

Since the concentrations of sodium and chloride in shark cells and extracellular fluids are similar to those of freshwater fishes, it can be inferred that sharks need to acquire these ions from the environment just like freshwater fish. Therefore, sodium and chloride will diffuse through the shark's gills from seawater down their concentration gradient to maintain proper levels. Option A is incorrect because the tissues of sharks are already isotonic to seawater, so they do not need to take up additional sodium and chloride from seawater. Option C is incorrect because it is not mentioned in the passage that sharks conserve sodium and chloride. Option D is incorrect because the passage does not mention the elimination of sodium and chloride through the gills.

Question 8

What is the function of the shark rectal gland?

Accepted Answer

The shark rectal gland is involved in osmoregulation, specifically in maintaining the balance of water and salt in the body. This allows sharks to live in a hypertonic environment, where the salt concentration is higher than their blood. The gland secretes a concentrated salt solution, which helps eliminate excess salt from the body while retaining necessary electrolytes.

Question 9

Freshwater fish live in a hypotonic environment.To maintain homeostasis in this environment,they must

Accepted Answer

Freshwater fish excrete large quantities of water to prevent excess water from accumulating in their bodies due to the hypotonic environment.

Question 10

The force driving simple diffusion is

Accepted Answer

The force driving simple diffusion is a concentration gradient. This means that molecules will spontaneously move from an area of higher concentration to an area of lower concentration until equilibrium is reached. No energy or pumps are required for simple diffusion. ATP, phosphorylated protein carriers, and transmembrane pumps are involved in facilitated diffusion or active transport, but not simple diffusion.

Question 11

Which of the following is an example of osmoregulation?

Accepted Answer

Osmoregulation is the process of regulating the concentration of solutes and water in an organism's body fluids. The contractile vacuole of a Paramecium is an example of osmoregulation as it pumps out excess water that enters the cell by osmosis, regulating the concentration of solutes and water in the cell. Option A is incorrect as two solutions being isotonic does not involve any regulation. Option C is incorrect as type 2 diabetes mellitus is a metabolic disorder, not related to osmoregulation.

Question 12

Table 42.1  
 
-Refer to Table 42.1: Because the shark rectal gland functions only when ATP molecules are present,what can you infer about the movement of Na⁺,K⁺,and Cl⁻?

Accepted Answer

The fact that the shark rectal gland functions only when ATP molecules are present implies that the movement of Na⁺, K⁺, and Cl⁻ into the rectal gland is an active process that requires energy in the form of ATP. This suggests that the rectal gland is actively transporting these ions from an area of lower concentration to a region of higher concentration, which is against their concentration gradient. Therefore, choice A is the best answer.

Question 13

Salmon eggs hatch in freshwater.The fish then migrate to the ocean (a hypertonic solution)and,after several years of feeding and growing,return to freshwater to breed.How can these organisms make the transition from freshwater to ocean water and back to freshwater?

Accepted Answer

Different gill cells are involved in osmoregulation in freshwater than in salt water, allowing salmon to adapt to different environments.

Question 14

Freshwater fish reside in hypotonic environments.They do not drink water,and they excrete large volumes of hypotonic urine in an effort to osmoregulate.How do they obtain an adequate supply of electrolytes?

Accepted Answer

The answer of Freshwater fish reside in hypotonic environments.They do...

Question 15

Paramecia live in pond water (a hypotonic environment).They have a structural feature,a contractile vacuole,that enables them to osmoregulate.If you observed paramecia in the following solutions,at which sucrose concentration would you expect the contractile vacuole to be most active?

Accepted Answer

The answer of Paramecia live in pond water (a hypotonic...

Question 16

Gas exchange in insects takes place across the epithelium of the tracheae (a system of tubes).The tracheal system connects to the outside air by openings called spiracles.Muscles just inside each spiracle can control the opening to minimize water loss.What would happen if the muscles inside each spiracle were unable to function?

Accepted Answer

If the muscles inside each spiracle were unable to function, the spiracles would remain open and the insect would be unable to control the water loss through transpiration. This would lead to excessive water loss, which can cause dehydration and ultimately death. Therefore, the best choice is B - the spiracles would lock open.

Question 17

Terrestrial organisms lose water through evaporation.Why are desert locusts and flour beetles good organisms to use in studying mechanisms to regulate water loss?

Accepted Answer

Desert locusts and flour beetles are good organisms to use in studying mechanisms to regulate water loss because they live in environments where little to no water is available, which puts selective pressure on them to have efficient mechanisms for water conservation.

Question 18

Table 42.1  
 
-The intercellular concentration of three electrolytes is compared with the concentration of these electrolytes in fluid eliminated from the shark rectal gland in Table 42.1.Based on the data,which of the following is a likely function of the rectal gland?

Accepted Answer

The table shows that the concentration of Na⁺,K⁺,and Cl⁻ in fluid eliminated from the shark rectal gland is significantly higher than the intercellular concentration in shark tissues. This suggests that the rectal gland is able to concentrate these electrolytes, and therefore, option B is a likely function of the rectal gland. Option A is unlikely because metabolic waste is typically eliminated through other organs such as the kidneys. Option C is not supported by the data provided in the table. Option D is not supported by the data either since there is a measurable concentration of potassium in both the intercellular fluid and the fluid eliminated from the rectal gland.

Question 19

What role does Na⁺/K⁺-ATPase play in salt excretion by the shark rectal gland?

Accepted Answer

Na⁺/K⁺-ATPase pumps sodium out and potassium into cells across the basolateral membrane, creating a gradient that facilitates salt excretion in the shark rectal gland.

Question 20

Which of the following is an example of equilibrium?

Accepted Answer

Equilibrium refers to a state where there is no net movement of a substance across a membrane. In option A, the substance moves into and out of the cell at the same rate, indicating that there is no net movement, which is an example of equilibrium. Option B, C, and D involve the movement of a substance either with or against a concentration or electrochemical gradient, indicating that there is a net movement, which is not an example of equilibrium.

Quiz 42: Water and Electrolyte Balance in Animals