Episode Details

To see why that's impossible, we first need the rule that moves almost everything in and out of your cells for free. Then we'll watch the plant break it and find out what that costs.

Back to the plant: it isn't breaking the rule, it's paying to beat it. The listener can now state both definitions. Diffusion is movement from high to low concentration down a gradient, with no energy needed. Active transport is movement against the gradient, using energy from respiration. The listener can also say why the plant needs the second one.

Sources:

• https://www.tutorchase.com/answers/igcse/biology/how-do-alveoli-facilitate-efficient-gas-exchange
• http://igbiologyy.blogspot.com/2012/12/19-active-transport_5.html
• https://igcsebiology.com.my/topics/transport-in-plants/root-hair-cell-absorption/

Source: Episode 3 - Biology Level 8, In and Out of Cells (3/10)
Style: Exam prep
Length: 940 words, 6 min target
Generated: 2026-10-25