Lesson 4 ·Class 10 · Absorption by Roots — The Processes Involved · Sort Lab

Diffusion, Osmosis and Active Transport

Three ways in, and only one costs energy.

Sort each statement into the kind of transport it describes.

Sorted 0/11

All items sorted — check each bin.

Free play — sort every item into the bin it belongs in; each correct drop tells you why. Switch to when you're ready to test yourself.

Two questions settle almost every case. Is a membrane needed? And does it cost energy? Only active transport answers yes to the second.

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Selina ICSE: Absorption by Roots — The Processes Involved

What this lesson covers

Selina asks it directly: can diffusion be called passive transport? Work out why the answer is yes.

Fill the Active transport bin correctly.
Sort every statement.
Fill the Osmosis box — diffusion of water through a selectively permeable membrane.

Sort each statement into the kind of transport it describes.

Diffusion — Free spreading: Movement of any substance — solid, liquid or gas (It is the general case; osmosis is a special instance of it.); Needs no membrane at all (The permanganate in a beaker spreads with nothing in its way.); Always down a concentration gradient (From more concentrated to less — never the reverse.); A passive process needing no energy (Which is why it is often called passive transport.)
Osmosis — Water, through a membrane: Movement of the solvent — water — only (Selina puts it neatly: osmosis includes diffusion, but not the other way round.); Requires a selectively permeable membrane (Without one, the solute would simply spread too and it would just be diffusion.); What makes a plant cell turgid when placed in water (Water enters the concentrated cell sap and the cell swells against its wall.)
Active transport — Uphill, using energy: Can move a substance AGAINST its concentration gradient (This is the whole point of it, and why it must be paid for.); Requires energy from ATP (Uphill movement cannot happen for free.); Uses carrier proteins in the membrane (Specific carriers pick up the ion and carry it across.); How a root takes up minerals that are scarcer in the soil than in the root (The gradient runs the wrong way, so the plant must spend energy.)

Two questions settle almost every case. Is a membrane needed? And does it cost energy? Only active transport answers yes to the second.