OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What is the role of mineral ions in the absorption process?

1. They move in by diffusion only

2. They moving actively against a concentration gradient

3. They do not play a role in absorption

4. They are absorbed through osmosis

The correct answer is: They moving actively against a concentration gradient

Mineral ions play a crucial role in the absorption process, particularly in plant roots and animal intestines. The correct answer highlights that these ions often move actively against a concentration gradient. This process is known as active transport, which requires energy to transport mineral ions from a region of lower concentration (in the soil or intestinal lumen) to a region of higher concentration within the plant or animal cells. Active transport is essential for the uptake of vital minerals such as nitrates, phosphates, potassium, and magnesium, which are necessary for various biological functions—like photosynthesis, enzyme function, and overall cellular metabolism. By using energy to transport these ions, plants can ensure they have the essential nutrients even when they are present in low concentrations in the environment. The other options do not describe the correct role of mineral ions in absorption. While diffusion is a process through which some molecules move (often down a concentration gradient), it does not account for the energy-dependent aspect of mineral uptake. Osmosis specifically pertains to the movement of water, not mineral ions, and the claim that mineral ions do not play a role in absorption contradicts their established importance in biological systems.