A Level Biology Practice Exam 2025 – All-in-One Study Guide to Excel in Your A Levels!

Channel proteins play a crucial role in assisting cellular functions by providing a hydrophilic channel through a membrane. This is particularly important in the context of cellular homeostasis and communication. The hydrophilic nature of the channel allows polar and charged molecules, such as ions and water, to pass through the otherwise hydrophobic lipid bilayer of the cell membrane. This selective permeability is vital for maintaining the proper ion concentrations inside and outside the cell, which are necessary for various cellular processes, including nerve impulse transmission and muscle contraction.

In contrast, options like catalyzing reactions or regulating gene expression correspond to the roles of enzymes and transcription factors, respectively. Producing energy for the cell generally refers to the function of organelles like mitochondria, rather than channel proteins. Therefore, the primary function of channel proteins centers around facilitating the movement of substances across cell membranes.