Final answer:
Facilitated diffusion involves membrane proteins such as channel and carrier proteins that help polar molecules and ions pass through the plasma membrane's hydrophobic interior. This process does not require energy as it moves substances down their concentration gradient. Active transport, in contrast, requires energy to move substances against this gradient.
Step-by-step explanation:
Understanding Protein Diffusion in the Cell's Plasma Membrane
Facilitated diffusion is a biologically essential process where substances, that are impeded due to their polar nature or size from diffusing readily through the plasma membrane, are helped by membrane proteins. Substances such as ions, simple sugars, and amino acids utilize these membrane proteins to move down their concentration gradient without the expenditure of cellular energy.
The plasma membrane's hydrophobic interior prevents the free passage of polar molecules and ions, despite their concentration gradients. Carrier proteins and channel proteins play a critical role in facilitated diffusion. While channel proteins allow substances to pass through based on size and charge, being less selective, carrier proteins are highly selective and often transport only one specific type of molecule across the membrane.
This transport method does not require energy as it relies on the dissipation of potential energy inherent in the concentration gradients of materials. In contrast, active transport involves moving substances against their gradient, requiring energy in the form of ATP. Understanding these mechanisms of cell transport is fundamental to grasping how cells maintain homeostasis and respond to external stimuli.