Question

If a poison such as cyanide stopped the production of ATP, which of the following transport processes would cease? a. The movement of \(\mathrm{Na}^{+}\)out of a cell b. Osmosis c. The movement of \(\mathrm{K}^{+}\)out of a cell d. All of these

Short answer

If the production of ATP is stopped due to a poison such as cyanide, the transport processes that would cease are the movement of \(\mathrm{Na}^{+}\) out of a cell (option a) and the movement of \(\mathrm{K}^{+}\) out of a cell (option c), as they are part of the active transport process called sodium-potassium pump, which requires ATP. Osmosis (option b) would not cease, as it is a passive transport process that does not require ATP.

Step-by-step solution

Review of transport processes and ATP

There are two main types of cellular transport processes: passive transport and active transport. Passive transport does not require the use of energy (ATP) as it moves substances along their concentration gradient, e.g., osmosis. Active transport, on the other hand, requires energy (ATP) as it moves substances against their concentration gradient, e.g., sodium-potassium pump. Now let's analyze each option:

Option a. The movement of \(\mathrm{Na}^{+}\) out of a cell

The movement of \(\mathrm{Na}^{+}\) ions out of a cell is part of the process known as the sodium-potassium pump, which is an example of active transport. Since this process requires ATP to function, it would cease if the production of ATP is stopped due to the poison.

Option b. Osmosis

Osmosis is the movement of water molecules across a selectively permeable membrane, from an area of high water concentration to an area of low water concentration. It is an example of passive transport, as it does not require the use of energy (ATP). Thus, osmosis would not cease if the production of ATP is stopped.

Option c. The movement of \(\mathrm{K}^{+}\) out of a cell

Similar to option a, the movement of \(\mathrm{K}^{+}\) ions out of a cell is also part of the sodium-potassium pump, which requires ATP to function. Therefore, this process would cease if the production of ATP is stopped due to the poison.

Option d. All of these

Since we've analyzed each option individually, we can now conclude that options a and c are correct while option b is not. Therefore, option d (All of these) is not the correct answer.

Conclusion

Based on the analysis above, if the production of ATP is stopped due to a poison such as cyanide, the transport processes that would cease are: the movement of \(\mathrm{Na}^{+}\) out of a cell (option a) and the movement of \(\mathrm{K}^{+}\) out of a cell (option c). Osmosis (option b) would not cease, as it is a passive transport process that does not require the use of energy (ATP).

Key concepts

Active Transport

Active transport is a critical function in cellular biology, where cells use energy, typically from adenosine triphosphate (ATP), to move molecules across their membranes against the concentration gradient. This is akin to 'swimming upstream', and is essential for maintaining cellular equilibrium. Imagine a turnstile at a subway station that only lets you through when you insert a token; that's how active transport works, utilizing 'energy tokens' in the form of ATP.

For example, ions like sodium (a^+)) and potassium (k^+)) are often transported via active transport mechanisms. These ions are pivotal for numerous cellular functions, including nerve impulse transmission and muscle contraction.

Passive Transport

Unlike its energy-consuming counterpart, passive transport relies on the natural movement of substances from areas of higher concentration to areas of lower concentration. This process does not require the cell to expend ATP and occurs spontaneously. It's as if molecules are 'sliding down a hill' following the slope of their concentration gradient.

One of the most well-known types of passive transport is osmosis, the movement of water molecules. It is critical for maintaining fluid balance within and between cells. To visualize osmosis, picture a sponge soaking up water - the water moves into the sponge until it is fully saturated, no energy required.

Sodium-Potassium Pump

How It Works

The sodium-potassium pump is a specialized form of active transport, vital in animal cells. This pump functions as a cellular 'gatekeeper', exchanging sodium ions out of the cell and potassium ions into the cell. This trade-off maintains necessary concentrations of these ions, crucial for processes like electrical nerve impulse generation and muscle contraction.

Why ATP is Needed

For every cycle of the pump, 3 sodium ions are transported out, and 2 potassium ions are transported in, which requires energy. ATP steps in here, donating a phosphate group to the pump, thus energizing it to facilitate the movement of these ions. Without ATP, the pump would lose its power source, essentially 'shutting down' the ion gradients that are so essential to cell survival.

ATP in Cellular Processes

ATP, or adenosine triphosphate, is often referred to as the 'currency' of cellular energy - it's used by cells to 'pay' for energy-requiring activities. ATP is involved in various cellular processes, including active transport mechanisms like the mentioned sodium-potassium pump, muscle contraction, synthesis of compounds, and even cell division.

Think of ATP as a rechargeable battery that, when connected, provides the power needed for a toy to operate. In the same way, ATP supplies the energy for pumps within the cell membrane to function effectively. If ATP supply is ceased, such as by a toxin like cyanide, these energy-consuming cellular activities would come to a halt, much like a battery-operated toy turning off when its power source is exhausted.