Q.Explain the active absorption of minerals.

Step 1. Two general modes of mineral uptake. Minerals are absorbed by roots either passively, by simple or facilitated diffusion along their own concentration gradient (no energy needed), or actively, by an energy-requiring process that can move ions into the root even against their concentration gradient.

Step 2. What 'active' means here. In active absorption, root cells expend metabolic energy (ATP), generated through respiration, to import mineral ions from the soil solution into the cytoplasm. This is necessary specifically when the ion's concentration is already higher inside the root cell than in the surrounding soil water, since simple diffusion alone cannot move an ion 'uphill' against its own gradient.

Step 3. Mechanism. Membrane transport proteins — carriers and ion channels, the same broad class of proteins involved in facilitated diffusion for passive uptake — mediate this active transport, but in the active case their operation is coupled to cellular energy expenditure rather than being purely gradient-driven. …

Contrast active (energy-dependent, against-gradient) with passive (diffusion-driven, along-gradient) mineral uptake, describe the carrier-medi …

• Describing active absorption of water (root pressure mechanism, section 6.8b) instead of active absorption of minerals, which the question specifically asks about. …