Secondary active transport

Definition

Secondary active transport is a process that moves ions or molecules across a cell membrane against their concentration gradient, utilizing the energy stored in the form of an electrochemical gradient created by primary active transport. This method is essential for transporting nutrients and ions that are crucial for various cellular functions, relying on the coupling of the movement of one substance down its gradient to drive the movement of another substance against its gradient.

5 Must Know Facts For Your Next Test

1. Secondary active transport relies on the energy generated by primary active transport to function effectively.
2. This type of transport can be classified into symporters and antiporters based on the direction of movement for the solutes involved.
3. An example of secondary active transport is the sodium-glucose cotransporter, which moves glucose into cells while sodium ions move down their concentration gradient.
4. Unlike primary active transport, secondary active transport does not directly use ATP; instead, it uses the energy created by ion gradients.
5. Secondary active transport plays a vital role in processes such as nutrient absorption in the intestines and reabsorption of ions in the kidneys.

Review Questions

• How does secondary active transport differ from primary active transport in terms of energy use and mechanisms?
  • Secondary active transport differs from primary active transport primarily in its source of energy. While primary active transport directly utilizes ATP to move substances against their concentration gradient, secondary active transport relies on the energy stored in an electrochemical gradient created by primary active transport. This means that secondary active transport is dependent on the work done by primary active transporters to establish those gradients before it can function.
• What roles do symporters and antiporters play in secondary active transport, and can you provide examples?
  • Symporters and antiporters are two types of transport proteins that facilitate secondary active transport. Symporters move two different substances in the same direction across a membrane, such as glucose and sodium ions being transported together into cells. In contrast, antiporters move one substance into the cell while simultaneously transporting another out, like sodium-potassium pumps. Both mechanisms are essential for maintaining cellular homeostasis and nutrient uptake.
• Evaluate the significance of secondary active transport in physiological processes like nutrient absorption and ion balance in cells.
  • Secondary active transport is crucial for many physiological processes, particularly in nutrient absorption and ion balance within cells. For instance, in the intestines, secondary active transport mechanisms enable cells to absorb glucose against its concentration gradient using sodium ions. Additionally, this process helps maintain ionic balance in cells by ensuring that necessary ions like calcium and potassium are regulated effectively. The proper functioning of these mechanisms is vital for overall cellular health and metabolism.

Related terms

primary active transport:

A transport mechanism that directly uses ATP to move ions or molecules against their concentration gradient.

electrochemical gradient:

The combined effect of the concentration gradient and the electrical gradient across a membrane that influences the movement of ions.

symporter: A type of transporter that moves two or more different substances in the same direction across a membrane during secondary active transport.