Question

Facilitated diffusion requires to transport substance across membrane. (a) Special membrane protein (b) ATP (c) Protein inhibitor (d) All of these

Short answer

The correct answer to the question is (a) Special membrane protein as these proteins assist in the process of facilitated diffusion, which doesn't require energy (ATP) or any protein inhibitors.

Step-by-step solution

Understand Facilitated Diffusion

Facilitated diffusion is a type of passive transport that does not require the input of cellular energy. Instead, it uses special proteins embedded in the cell membrane to help transport substances across.

Evaluate the Options

Looking at the options, (a) Special membrane protein, (b) ATP, and (c) Protein inhibitor, it can be concluded by understanding the process of facilitated diffusion that it does involve special membrane proteins but does not require ATP or any protein inhibitors since it is not an energy dependent process and it allows substances to move along their concentration gradient.

Conclusion

Considering the above statements, the correct answer will be (a) Special membrane protein, because these proteins facilitate the diffusion process without the need for any cellular energy (ATP) or protein inhibitors.

Key concepts

Passive Transport

Passive transport is a fundamental way substances move across cell membranes without the need for energy input, unlike active transport which needs energy in the form of ATP. In passive transport, molecules naturally move from an area of higher concentration to one of lower concentration. This process is purely driven by the concentration gradient, meaning particles will spread out evenly over the available space until equilibrium is reached. The movement continues until there is no longer a concentration gradient, and equilibrium is achieved. This could include processes like simple diffusion which occurs naturally due to molecular motion.

• Does not require energy
• Molecules move from high to low concentration
• Relies on the concentration gradient
• Examples: Simple diffusion, osmosis

Facilitated diffusion, which is a type of passive transport, uses proteins to help these molecules cross the membrane more efficiently.

Membrane Proteins

Membrane proteins play a crucial role in facilitated diffusion. They are integral proteins embedded within the cell membrane, making it possible for specific molecules to pass that would otherwise be unable to cross the hydrophobic core of the lipid bilayer. These proteins are specific to certain molecules, providing a selective pathway for diffusion.

• Types of membrane proteins include carrier proteins and channel proteins.
• Carrier proteins change shape to shuttle molecules across the membrane.
• Channel proteins form pores that allow specific molecules to pass through.

The involvement of membrane proteins ensures that facilitated diffusion is both a selective and efficient process for transporting substances like ions and larger polar molecules that cannot pass through the membrane on their own, without energy usage.

Concentration Gradient

The concentration gradient is a key driving force in passive transport and facilitated diffusion. It refers to the gradual difference in the concentration of solutes in a solution between two regions. Substances naturally move down their concentration gradient, from high concentration areas to low concentration areas, in an attempt to achieve balance or equilibrium. This process is passive since it doesn't require any energy input to occur.

• Drives the passive movement of molecules
• Exists when there’s a difference in solute concentration across regions
• Facilitated by selective membrane proteins

In biological systems, maintaining concentration gradients is essential for functions such as nutrient uptake and waste removal. Facilitated diffusion exploits these concentration gradients, allowing necessary molecules to move efficiently across cell membranes without energy expenditure.