**Question:** True about facilitated diffusion are A/E:

A. It requires energy (ATP)
B. It occurs in the nucleus
C. It is passive transport of ions
D. It is specific for glucose only

**Core Concept:**
Facilitated diffusion is a type of passive transport in which molecules move down their concentration gradient from an area of high concentration to an area of low concentration. It does not require energy (ATP), but rather takes advantage of the concentration gradient to move molecules across cell membranes. This process allows for the efficient transport of various molecules, including ions, glucose, and other small polar molecules, without the need for active transport or enzymatic reactions.

**Why the Correct Answer is Right:**
Option A is incorrect because facilitated diffusion does not require energy (ATP) for its mechanism. Instead, it is a passive transport process driven by the concentration gradient.

Option B is wrong as facilitated diffusion occurs throughout the cell, including the plasma membrane and organelles like mitochondria, but not specifically in the nucleus.

Option C is accurate as facilitated diffusion is a passive transport process, meaning it does not involve active transport or enzymatic reactions. It allows for the passive movement of ions across cell membranes, contributing to proper cellular function and homeostasis.

Option D is incorrect as facilitated diffusion is not limited to glucose transport only; it also involves other small polar molecules and ions.

**Why Each Wrong Option is Incorrect:**

Option A (requires energy): Facilitated diffusion does not require energy (ATP) for its mechanism.

Option B (limited to nucleus): Facilitated diffusion occurs throughout the cell and organelles like mitochondria, not just in the nucleus.

Option C (passive transport of ions): Facilitated diffusion is a passive transport process that allows for the passive movement of ions across cell membranes, contributing to cellular function and homeostasis.

Option D (limited to glucose): Facilitated diffusion involves not only glucose but also other small polar molecules and ions.

**Clinical Pearls:**

Facilitated diffusion plays a vital role in cellular processes, enabling the passive transport of molecules across cell membranes. It contributes to essential functions like maintaining ion homeostasis, facilitating glucose uptake in cells, and allowing the transport of small polar molecules and ions. Understanding this process is crucial for understanding cellular function and the proper functioning of cells and tissues in the body.