Problem 27 - Objective Biology for NEET

Question

The major similarity between active transport and facilitated diffusion is that (a) Both consume ATP (b) Both are passive (c) Both are non-selective (d) Both require membrane proteins

Step-by-Step Solution

Answer

The major similarity between active transport and facilitated diffusion is that both require membrane proteins.

Step 1: Understand Active Transport

Active transport is a type of cellular transport where substances move against their concentration gradient. This process requires the cell to expend energy, typically in the form of ATP (Adenosine TriPhosphate), making it an energy-dependent process. Also, it requires membrane proteins to help substances move across the cell membrane.

Step 2: Understand Facilitated Diffusion

Facilitated diffusion is also a type of cell transport where substances move down or along their concentration gradient, which means they move from an area of higher concentration to an area of lower concentration. This process does not require any energy because substances are moving along their natural gradient. However, like active transport, facilitated diffusion also requires the aid of membrane proteins to move larger or charged molecules across the cell membrane.

Step 3: Identify the Major Similarity

By comparing the nature of both processes, it's clear that the major similarity between active transport and facilitated diffusion is that they both require the presence of membrane proteins to transport substances across the cell membrane. So, the correct answer is option (d) Both require membrane proteins

Key Concepts

Active Transport

Active transport is a crucial cellular operation in which cells move molecules across their membranes from an area of lower concentration to an area of higher concentration. This process goes against what would naturally occur, hence requiring an input of energy.

Unlike passive transport mechanisms, active transport involves the use of energy in the form of adenosine triphosphate (ATP). ATP provides the necessary power to change the shape of membrane proteins that shuttle the molecules or ions across the membrane. These proteins are often referred to as 'pumps' because of their role in actively moving substances in and out of the cell. An example of active transport is the sodium-potassium pump that maintains the electrochemical gradient in nerve cells.

Facilitated Diffusion

Facilitated diffusion is a passive transport process that allows molecules that cannot directly diffuse through the cell membrane to move across it with the help of membrane proteins.

These molecules generally include those that are large, polar, or charged and therefore require a specific transport protein to create a passageway. Unlike active transport, facilitated diffusion does not use cellular energy but rather exploits the concentration gradient, moving substances from an area of higher concentration to one of lower concentration. It is a selective process, meaning that transport proteins are specific to the molecules they transport. An example of facilitated diffusion is the movement of glucose into cells using a specific carrier protein.

Membrane Proteins

Membrane proteins play a multifaceted role in cell transport and are fundamental to both active transport and facilitated diffusion.

These proteins may act as channels or carriers to aid in the movement of substances across the cell membrane. Channels provide a hydrophilic path for the movement of ions and small molecules, while carriers often change their shape to transfer their cargo from one side of the membrane to the other. It's important to note that the function of membrane proteins is highly specific, acting on only certain molecules, which is why certain medications and molecules can target specific carrier proteins without affecting others.

Concentration Gradient

The concentration gradient is a term used to describe the variation in the concentration of a substance across a space or a membrane.

In the context of cellular transport, substances generally move from an area of high concentration to an area of low concentration in an attempt to achieve equilibrium. This movement can occur passively, as in diffusion and facilitated diffusion, or actively if energy is used to move substances against the concentration gradient. Understanding concentration gradients is crucial in biology as they influence the direction and rate of diffusion, osmosis, and active transport processes within the body.