Question

What part of the cell membrane is necessary for facilitated diffusion? Describe one way this process is important within the body. (p. 55)

Short answer

Answer: The integral membrane proteins, particularly channel proteins and carrier proteins, play a crucial role in facilitated diffusion by helping transport substances across the membrane. This process is important within the body as it helps maintain glucose homeostasis, ensuring adequate glucose levels for proper functioning and survival of cells.

Step-by-step solution

Identify the part of the cell membrane responsible for facilitated diffusion

The part of the cell membrane necessary for facilitated diffusion is the integral membrane proteins, particularly channel proteins and carrier proteins. These proteins help in transporting substances across the membrane that otherwise cannot easily pass through the lipid bilayer.

Describe the process of facilitated diffusion

Facilitated diffusion is a type of passive transport where substances move across the cell membrane down their concentration gradient, with the help of channel proteins or carrier proteins. This process does not require energy as the substances are moving from a region of higher concentration to a region of lower concentration.

Explain the importance of facilitated diffusion within the body

One importance of facilitated diffusion within the body is maintaining glucose homeostasis. In this process, GLUT (Glucose Transporter) carrier proteins help in transporting glucose across the plasma membrane of cells. This is crucial because glucose serves as the primary source of energy for cells, and maintaining adequate glucose levels is essential for proper functioning and survival of the cells in the body.

Key concepts

Integral Membrane Proteins

Integral membrane proteins play a pivotal role in facilitated diffusion. These proteins are embedded within the cell membrane, providing a pathway for molecules that cannot easily pass through the lipid bilayer.
They are essential because the lipid bilayer of a cell membrane is hydrophobic, making it difficult for hydrophilic substances or larger molecules to pass through.
Integral proteins span the entire membrane and create channels or act as carriers to allow these molecules to move across the membrane.

• They are permanently attached to the cell membrane.
• Their structure is specifically adapted to transport specific ions or molecules.
• Some function as transport channels, while others serve as carriers that change shape to move molecules in or out of the cell.

These proteins are critical for processes like cell communication and nutrient uptake, ensuring that essential substances like ions, glucose, and amino acids reach inside the cell where they are needed.

Channel Proteins

Channel proteins are specific types of integral membrane proteins that facilitate the passage of molecules through the cell membrane. They act like gates, forming open pathways across the lipid bilayer for certain ions and molecules to pass through.
The flow through channel proteins is usually facilitated by the concentration gradient across the membrane, meaning they move substances from higher to lower concentration without the use of cellular energy.

• The channels are often specific to a particular substance, allowing selective permeability.
• Many channel proteins can open or close in response to certain signals, regulating the flow into and out of the cell.

Facilitated diffusion via channel proteins is swift and vital for cellular activities, like transmitting nerve impulses and muscle contraction. Without them, essential ions could not easily enter or exit cells.

Glucose Homeostasis

Glucose homeostasis is the process of maintaining stable glucose levels in the blood, an important aspect of energy regulation in the body. Proper glucose balance ensures that the body has sufficient energy for metabolic activities while avoiding the dangers of too much or too little glucose in the blood.
During facilitated diffusion, glucose is transported into cells with the help of integral membrane proteins known as GLUT (Glucose Transporter) proteins.

• GLUT proteins enable glucose to enter cells by moving down its concentration gradient.
• This process does not require energy, as it harnesses the natural movement from high to low concentration.
• Maintaining glucose homeostasis is crucial for energy supply to cells, particularly in brain and muscle tissues.

Any disruption in glucose homeostasis can lead to health problems such as diabetes, so the efficient working of these transporters is critical for overall health and cellular function.