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Chapter 32: Problem 1

Why is the sodium ion at the highest concentration in extracellular fluid? a. Sodium diffuses freely through the cell membrane. b. The sodium/potassium pump removes sodium ions from the cell. c. The blood contains a high concentration of sodium. d. Sodium is actively taken up by the cells for use in the cytoplasm

Short Answer

Expert verified
b. The sodium/potassium pump removes sodium ions from the cell.

Step by step solution

01

- Understand the Role of the Sodium/Potassium Pump

The sodium/potassium pump is a vital membrane protein that helps maintain the balance of sodium and potassium ions across the cell membrane. It actively transports sodium ions out of the cell and potassium ions into the cell using ATP for energy.
02

- Examine Answer Choices

Look at each answer option: a. Sodium diffuses freely through the cell membrane. b. The sodium/potassium pump removes sodium ions from the cell. c. The blood contains a high concentration of sodium. d. Sodium is actively taken up by the cells for use in the cytoplasm.
03

- Evaluate Answer a

Sodium ions do not diffuse freely through the cell membrane; they require channels or pumps to pass through the lipid bilayer.
04

- Evaluate Answer b

This is correct. The sodium/potassium pump actively removes sodium ions from the cell, resulting in a higher concentration of sodium ions in the extracellular fluid.
05

- Evaluate Answer c

While blood may contain sodium, this is not the main reason for the high extracellular concentration. The active transport by the sodium/potassium pump is the key process.
06

- Evaluate Answer d

Sodium is not actively taken up by cells for use; the cells actively expel sodium to maintain cellular functions and osmotic balance.
07

- Conclusion

Based on the evaluations, the correct answer is that the sodium/potassium pump removes sodium ions from the cell, leading to a higher concentration of sodium in the extracellular fluid.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Cell Membrane Transport
Cell membrane transport refers to the movement of substances in and out of cells through the cell membrane. This process is crucial for maintaining the proper function and homeostasis of the cell. There are two main types of transport: passive and active.

  • **Passive Transport:** This type of transport does not require energy. Substances move along the concentration gradient (from higher to lower concentration). Examples include diffusion and osmosis.
  • **Active Transport:** This type requires energy (usually in the form of ATP) to move substances against the concentration gradient (from lower to higher concentration). The sodium/potassium pump is a prime example of active transport. It moves sodium out of the cell and potassium into the cell.

Understanding these transport mechanisms is essential in grasping how cells maintain their internal environment and interact with their surroundings.
Ion Concentration Balance
Ion concentration balance is the process by which cells regulate the concentration of various ions inside and outside of the cell. This balance is vital for cellular function, such as electrical signaling in neurons, muscle contraction, and maintaining osmotic balance.

  • **Na+/K+ Pump:** This pump is a key player in maintaining ion concentration balance. It expels three sodium (Na+) ions out of the cell while bringing in two potassium (K+) ions. This creates a higher concentration of sodium outside the cell and a higher concentration of potassium inside the cell.
  • **Membrane Potential:** The differences in ion concentrations create an electrical potential across the cell membrane, known as the membrane potential. This potential is crucial for the transmission of electrical signals in nerve and muscle cells.
  • **Osmotic Balance:** By controlling the movement of ions like sodium and potassium, cells can also regulate water movement, thus maintaining osmotic balance. This is vital for preventing cell swelling or shrinkage.

In summary, the sodium/potassium pump is crucial for maintaining ion concentration balance and, by extension, overall cellular homeostasis.
Extracellular Fluid
Extracellular fluid (ECF) is the fluid environment outside the cells. It provides the necessary surroundings for cells to receive nutrients, remove waste, and communicate with other cells.

  • **Composition:** ECF includes plasma (the liquid part of blood) and interstitial fluid (the fluid between cells). It is rich in sodium ions, chloride ions, and bicarbonate, and contains fewer potassium ions compared to the cytoplasm.
  • **Importance of the Sodium/Potassium Pump:** The pump maintains a high concentration of sodium in the ECF by actively transporting sodium out of the cells. This is crucial because sodium plays a significant role in fluid balance, electrical signaling, and nutrition transport.
  • **Homeostasis:** The ECF is essential for maintaining homeostasis. The proper balance of electrolytes is maintained through intricate control mechanisms, including the action of the sodium/potassium pump, to ensure that cells function correctly.

Keeping the extracellular fluid balanced and rich in sodium ions is essential for various bodily functions and helps support cellular activity and overall health.

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Most popular questions from this chapter

How are the formation of urea and uric acid similar and different? a. In birds, reptiles, and insects, the urea cycle converts ammonia to urea. In mammals, the uric acid cycle converts ammonia to uric acid. Formation of urea from ammonia requires less energy and is less complex than uric acid formation. b. In mammals, the urea cycle converts ammonia to urea. In birds, reptiles, and insects, the uric acid cycle converts ammonia to uric acid. Formation of urea from ammonia requires more energy and is less complex than uric acid formation. c. In mammals, the urea cycle converts ammonia to urea. In birds, reptiles, and insects, the uric acid cycle converts ammonia to uric acid. Formation of urea from ammonia requires less energy and is more complex than uric acid formation. d. In mammals, the urea cycle converts ammonia to urea. In birds, reptiles, and insects, the uric acid cycle converts ammonia to uric acid. Formation of urea from ammonia requires less energy and is less complex than uric acid formation.

In the loop of Henle, the permeability of the membrane changes. The descending limb and ascending limb are permeable to which of the following, respectively? a. solutes and water b. proteins and solutes c. water and proteins d. water and solutes

Birds and reptiles convert toxic ammonia to uric acid or the closely related compound guanine (guano), reflecting the close evolutionary ancestry of these groups. However, terrestrial arthropods also convert ammonia to uric acid. This is as opposed to fish, which excrete ammonia directly, without converting it to another substance. However, the conversion of ammonia to uric acid requires more energy and is much more complex than the conversion of ammonia to urea. What do these findings suggest about why these organisms evolved the conversion of ammonia to uric acid? a. To evolve the ability to switch between uric acid and ammonia excretion b. To conserve water to allow them to persist on land c. For reduction in excretion of ammonia d. For excretion of higher concentrations of ammonia

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 cilia of the protonephridia, and why? a. The renal artery, because it facilitates the exchange of nutrients with the blood b. The convoluted tubule, because it facilitates the exchange of nutrients with the blood c. The glomerulus, because it facilitates filtering of the blood d. The ureter, because it facilitates filtering of the blood

Which cells or organs secrete renin? a. granular cells of the juxtaglomerular apparatus b. the kidneys c. the nephrons d. water-reabsorbing cells of the collecting duct
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