Question 1

Blood plasma in birds is about ______ of the ECF.

Accepted Answer

Blood plasma in birds constitutes about 40% of the extracellular fluid (ECF). This proportion is significant as it highlights the role of blood plasma in the overall fluid balance and transport of substances within a bird's body.

Question 2

In vertebrates

Accepted Answer

The plasma and the interstitial fluid, which are both components of the extracellular fluid (ECF) in vertebrates, indeed have similar compositions, especially in terms of ion concentrations and nutrients, differing mainly in protein content.

Question 3

Which of the following statements is NOT true?

Accepted Answer

C) is not true because in most organisms, K+ (potassium) is the primary ion in the intracellular fluid (ICF), not Na+ (sodium). Sodium is the primary ion in the extracellular fluid (ECF).

Question 4

The net transfer of water between the interstitial fluid and ICF across the plasma membrane

Accepted Answer

The net transfer of water between the interstitial fluid and the intracellular fluid (ICF) across the plasma membrane is mainly driven by osmosis, which is the movement of water through a semipermeable membrane from an area of low solute concentration to an area of high solute concentration. This process is primarily influenced by the difference in osmotic force (osmotic pressure) between the ICF and the interstitial fluid, rather than by channel proteins or hydrostatic pressure differences.

Question 5

When sodium ions enter a cell

Accepted Answer

When sodium ions enter a cell, the osmotic pressure inside the cell increases because the concentration of solutes inside the cell becomes higher. This osmotic pressure difference causes water molecules to move into the cell to balance the concentration gradient, often accompanying the sodium ions. As a result, the cell may become swollen due to the influx of water, leading to all the mentioned effects occurring simultaneously.

Question 6

Insects prevent water loss and disturbance in the osmotic balance in cells by

Accepted Answer

Insects have a cuticle, a protective, waxy or hard layer covering the epidermis of plants, fungi, and some invertebrates, including insects. This cuticle acts as a barrier to water loss, helping to prevent dehydration and maintain osmotic balance within their cells.

Question 7

Which of the following is NOT correctly paired?

Accepted Answer

Methylamines (such as TMAO) and proline are both types of organic osmolytes, but they belong to different categories. Methylamines are known for their role in counteracting the effects of urea and stabilizing proteins, while proline is a compatible solute that helps in osmoregulation but they are not directly paired as a counteracting solute relationship like TMAO with urea.

Question 8

To overcome long-term osmotic challenges caused by osmotic changes in the external environment, osmoconformers

Accepted Answer

Osmoconformers adjust to osmotic changes by raising the level of organic osmolytes in their intracellular fluid (ICF), which increases the osmotic pressure of the ICF without significantly altering the ion concentration. This strategy helps them maintain osmotic balance with their environment.

Question 9

Important organic osmolytes in marine osmoconformers are

Accepted Answer

Marine osmoconformers use a variety of organic osmolytes to regulate their internal osmotic pressure in response to changes in their external environment. These osmolytes include polyols and sugars, amino acids like glycine and taurine, methylamines and methylsulfonium compounds, as well as urea. Each of these compounds helps in maintaining cellular function and integrity under varying osmotic conditions.

Question 10

Which among the following byproducts of bacterial action on an organic osmolyte in fish is used as an indicator of fish spoilage?

Accepted Answer

Trimethylamine (TMA) is a byproduct of bacterial action on trimethylamine oxide (TMAO), an organic osmolyte found in fish. The presence of TMA is commonly used as an indicator of fish spoilage because it produces a strong, fishy odor that is easily detectable.

Question 11

Why do marine osmoconformers use organic osmolytes in their ICF to attain osmotic balance instead of the more easily available inorganic osmolytes such as sodium, potassium and chloride ions?

Accepted Answer

Organic osmolytes do not interfere with the structure and function of proteins and other macromolecules within the cell, allowing cells to maintain their internal environment without compromising the functionality of these crucial molecules.

Question 12

Stenohaline osmoconformers such as sea anemones and sea stars

Accepted Answer

Stenohaline osmoconformers, including sea anemones and sea stars, have a limited tolerance to changes in the salinity of their surrounding seawater, meaning they thrive in environments with relatively stable salinity levels.

Question 13

Animals living in intertidal zones are

Accepted Answer

Euryhaline organisms can tolerate a wide range of salinities, which is a necessary adaptation for life in intertidal zones where the salinity of the water can vary significantly due to the mixing of sea water with fresh water from rain, rivers, or estuaries.

Question 14

Marine sharks and rays

Accepted Answer

Marine sharks and rays are ureosmotic conformers (A) because they maintain their body fluids at an osmotic pressure similar to seawater by retaining urea. They also have ICF and ECF with equal or slightly higher osmotic pressure than seawater (C) due to the presence of urea and other solutes.

Question 15

In sharks and rays TMAO

Accepted Answer

TMAO (trimethylamine N-oxide) counteracts the toxic effects of urea and is present in a 2:1 ratio with urea in sharks and rays, making both options A and B correct.

Question 16

Osmoregulators:

Accepted Answer

Osmoregulators maintain a relatively steady extracellular fluid (ECF) osmotic pressure despite changes in the external environment's osmotic pressure. This allows them to control their internal osmotic conditions, ensuring their cells function properly regardless of the surrounding water's osmolarity.

Question 17

Muscle is about _________ water.

Accepted Answer

Muscle tissue is approximately 75% water, which helps give muscles their size and shape and aids in metabolic processes.

Question 18

Fresh water vertebrates

Accepted Answer

Fresh water vertebrates are hyper-osmotic regulators, produce large volumes of hypotonic urine, maintain lower internal osmolarities in order to minimize water intake, and are adapted to take in ions of sodium, chlorine and calcium by means of gills, chloride cells and moist skin.

Question 19

In osmoregulators such as mammals

Accepted Answer

Osmoregulators like mammals maintain a stable internal environment despite external changes. The kidneys play a crucial role in monitoring and controlling the osmotic balance between extracellular fluid (ECF) and intracellular fluid (ICF). When the ECF becomes hypertonic, cells may lose water, leading to potential dehydration. To counteract this, some cells can undergo regulatory volume increase (RVI) to compensate for water loss. Thus, changes in the ECF directly influence the ICF, making all the statements correct.

Question 20

Camels are perfectly adapted to desert conditions because

Accepted Answer

Camels are highly adapted to desert conditions through various physiological mechanisms. They can tolerate significant loss of body water (up to 30%) without severe consequences, slow down their metabolism to cope with dehydration, maintain plasma volume even when interstitial fluid becomes hypertonic, and their cells can handle rapid rehydration without going into osmotic shock. These adaptations collectively enable camels to thrive in harsh desert environments.

Quiz 13: Fluid and Acid-Base Balance