Question

What provides the energy for active transport? Describe one way this process is important within the body. (pp. 55–56)

Short answer

Answer: The energy for active transport is provided by adenosine triphosphate (ATP). Active transport is essential for various functions within the body, such as maintaining the proper concentration of ions. An example of its importance is the sodium-potassium pump, which is vital for nerve impulse transmission and proper functioning of the nervous system, including muscle movement and sensory perception.

Step-by-step solution

Understanding Active Transport

Active transport is a process in which ions or molecules move across a cell membrane against their concentration gradient, requiring energy input from the cell. This process allows cells to maintain proper balance and function effectively.

Source of Energy for Active Transport

The primary source of energy for active transport is adenosine triphosphate (ATP), which is a molecule used for energy storage and transfer in cells. ATP provides the required energy by undergoing a reaction that causes it to lose one of its phosphate groups, converting it into adenosine diphosphate (ADP). This release of phosphate provides energy to drive the active transport process.

One Important Function of Active Transport

An essential function of active transport within the body is maintaining the proper concentration of ions, such as sodium and potassium, across cell membranes. The sodium-potassium pump is an example of active transport that plays a crucial role in nerve cells. This pump moves sodium ions out of the cell while moving potassium ions into the cell, maintaining an electrochemical gradient that is essential for nerve impulse transmission. This, in turn, allows for the proper functioning of the nervous system, including tasks such as muscle movement and sensory perception.

Key concepts

Adenosine Triphosphate (ATP)

Adenosine Triphosphate (ATP) is a vital molecule that acts as the main energy currency in cells. It stores and transports chemical energy within cells, powering various biological processes that are essential for life. The structure of ATP consists of an adenosine molecule combined with three phosphate groups. The energy stored in ATP is released when the bond between the second and third phosphate group is broken, converting ATP into adenosine diphosphate (ADP). This process releases energy that the cell can harness for power.

ATP plays a crucial role in active transport, which involves the movement of substances across cell membranes against their concentration gradient. This means that cells can absorb nutrients and remove waste even when it's against the direction of natural diffusion.

• Stores energy in easily accessible form.
• Releases energy through phosphate bond breakage.
• Enables cells to perform work, such as muscle contraction and cellular transport.

Without ATP, cells would not have the energy needed to perform many critical functions, such as active transport, making it indispensable for life.

Sodium-Potassium Pump

The sodium-potassium pump is a specialized protein found in cell membranes that performs active transport. Its primary function is to maintain the proper concentration of sodium and potassium ions inside and outside the cell.

This pump uses energy from ATP to move sodium ions out of the cell and potassium ions into the cell. It typically moves three sodium ions out for every two potassium ions moved in, which helps create an electrochemical gradient across the cell membrane. This gradient is crucial for various cellular functions, particularly in nerve and muscle cells.

• Maintains ion balance essential for cell function.
• Creates an electrochemical gradient necessary for nerve signal transmission.
• Uses energy from ATP to perform its tasks.

The sodium-potassium pump is vital not only for maintaining ionic equilibrium but also for ensuring that nerve cells can send and receive signals properly.

Nerve Impulse Transmission

Nerve impulse transmission is the process by which nerve cells, or neurons, send signals throughout the body. This process is fundamental for activities such as thinking, moving muscles, and perceiving the environment. It relies heavily on the sodium-potassium pump.

When a nerve signal is initiated, specific ion channels in the neuron's membrane open, allowing sodium ions to rush into the cell. This influx of sodium causes a change in the electrical charge of the nerve cell's membrane, creating what is known as an action potential. Subsequently, potassium channels open, allowing potassium ions to move out of the cell, restoring the initial electrical state.

• Relies on movement of sodium and potassium ions.
• Involves action potentials for signaling.
• Essential for communication between neurons.

The sodium-potassium pump resets the ion concentrations to their resting state after a nerve impulse, ensuring the neuron is ready for the next signal. This process is crucial for the high-speed communication required for rapid, coordinated responses by the nervous system.