Question

What molecule is required to control the balance of sodium and water within a cell? A. \(\mathrm{NaCl}\) B. Glucose C. ATP D. Urea

Short answer

C. ATP

Step-by-step solution

Understand the Question

The question asks to identify a molecule required to control the balance of sodium and water within a cell.

Evaluate the Options

Examine each option to determine its role in the body and cellular processes: - \(\mathrm{NaCl}\): Common table salt, involved in the regulation of sodium but not directly controlling balance within the cell.- Glucose: A sugar molecule used for energy.- ATP: The energy currency of the cell used in many cellular processes.- Urea: A waste product formed in the liver.

Identify the Correct Molecule

Out of the given options, ATP (Adenosine Triphosphate) is the molecule that powers sodium-potassium pumps in cell membranes. These pumps actively transport sodium out of and potassium into the cell, which helps to control the balance of sodium and water.

Conclusion

ATP is essential for driving the sodium-potassium pumps that maintain the balance of sodium and water within the cell.

Key concepts

ATP Function

ATP, or Adenosine Triphosphate, is often referred to as the 'energy currency' of the cell. This is because ATP stores and transports chemical energy within cells. When a cell needs energy, it breaks down ATP into ADP (Adenosine Diphosphate) and a phosphate group, releasing energy that can be used for various cellular processes.

ATP is crucial for many functions such as:

• Muscle contraction
• Protein synthesis
• Transporting molecules across cell membranes, like in the sodium-potassium pump

By providing energy, ATP allows cells to maintain their functions and stay alive.

Sodium-Potassium Pump

The sodium-potassium pump is a special protein found in the cell membrane. This pump uses energy from ATP to transport sodium ions (Na⁺) out of the cell and potassium ions (K⁺) into the cell. It's an active transport mechanism because it requires energy to function.

Here is how the sodium-potassium pump works:

• Three sodium ions bind to the pump from the inside of the cell.
• ATP is used to change the shape of the pump, moving sodium ions out of the cell.
• Two potassium ions from outside the cell bind to the pump.
• The pump returns to its original shape, transporting potassium into the cell.

This process helps maintain a balance of sodium and potassium ions, which is vital for numerous cell functions, including cell volume regulation and electrical signaling in nerves and muscles.

Cell Membrane Transport

Cell membrane transport is essential for maintaining homeostasis within the cell. The cell membrane is selectively permeable, meaning it controls what substances can enter or leave the cell. There are different types of transport mechanisms:

• **Passive Transport:** Does not require energy. Molecules move from an area of higher concentration to an area of lower concentration. Types include diffusion, osmosis, and facilitated diffusion.
• **Active Transport:** Requires energy (usually ATP). Molecules move against their concentration gradient, from an area of low concentration to an area of high concentration. The sodium-potassium pump is an example.

By using passive and active transport, cells can regulate their internal environment, allowing them to function correctly and respond to changes in their surroundings.