---
title: "Channel Proteins — AP Bio Definition & Exam Guide"
description: "Channel proteins are membrane tunnels that let ions and polar molecules cross the bilayer by facilitated diffusion. Key to permeability in AP Bio Unit 2."
canonical: "https://fiveable.me/ap-bio/key-terms/channel-proteins"
type: "key-term"
subject: "AP Biology"
---

# Channel Proteins — AP Bio Definition & Exam Guide

## Definition

Channel proteins are integral membrane proteins that form a tunnel across the entire phospholipid bilayer and allow specific molecules or ions to move across the cell membrane.

## Related Study Guides

- [2.4 Membrane Permeability](/ap-bio/unit-2/plasma-membranes/study-guide/1aW0ZDGzS56ism3BJwTi)
- [2.7 Tonicity and Osmoregulation](/ap-bio/unit-2/tonicity-osmoregulation/study-guide/i3qUckt9PGfT4pQlHq5B)

## Review

### Related Terms

- [Integral Proteins](/ap-bio/key-terms/integral-proteins): These are permanently attached within the plasma membrane. They perform various functions including acting as channels for transport of materials.
- Ion Channels: These are pore-forming membrane proteins whose functions include establishing a resting membrane potential, shaping action potentials and other electrical signals by gating the flow of ions across the cell membrane.
- [Transport Proteins](/ap-bio/key-terms/transport-proteins): These are involved in the movement of ions, small molecules, or macromolecules, such as another protein, across a biological membrane.