A Level Biology Practice Exam

What role do carrier proteins play in cellular function?

1. They assist in the synthesis of DNA

2. They transport substances through a membrane

3. They act as storage for genetic material

4. They generate energy within mitochondria

The correct answer is: They transport substances through a membrane

Carrier proteins are essential components of the cell membrane, responsible for facilitating the transport of specific substances across the membrane. This transport is crucial for maintaining cellular homeostasis, allowing cells to uptake necessary nutrients and expel waste products. Carrier proteins achieve this by binding to the molecules they transport, undergoing conformational changes that enable them to move the substances from one side of the membrane to the other. Unlike channels that provide a passage for substances to flow through, carrier proteins are more selective and often involve active transport mechanisms, which require energy to move substances against their concentration gradient. This functional role highlights their importance in cellular function, ensuring that essential ions and molecules are available inside the cell and that harmful substances are removed efficiently.