Summary
Highlights
Active transport is introduced as the movement of molecules against their concentration gradient, from a lower to a higher concentration, requiring cellular energy. This is contrasted with diffusion, which is a passive process where substances move down their concentration gradient without energy.
Active transport always occurs across a membrane and uses specialized proteins within the membrane to transfer molecules. The energy for this process comes from cellular respiration, primarily in the mitochondria, which breaks down glucose to release energy stored in ATP molecules. ATP acts like a battery, delivering energy to different parts of the cell.
Active transport is defined as the movement of molecules across a cell membrane from a region of lower concentration to a region of higher concentration, requiring energy from cellular respiration.
An example of active transport is shown in plant root hair cells. Plants need to absorb mineral ions like magnesium and nitrates from the soil. Since these minerals are often at a higher concentration inside the root hair cells than in the soil, they cannot be absorbed by diffusion. Instead, root hair cells use active transport to absorb these ions against their concentration gradient.
Root hair cells are adapted for active transport by having a large surface area for absorption due to their long, hair-like protrusions, and by containing numerous mitochondria to produce the large amount of energy (ATP) needed for active transport through cellular respiration.