Video Transcript
Membranes surrounding plant cells
are selectively permeable. What does this mean? (A) The membrane will have large
gaps for molecules to pass through. (B) The membrane will only allow
certain substances to move in or out of the cell. Or (C) the membrane can only be
permeated by large molecules.
Plants absorb the essential
nutrients that they need from their environment, which can then be transported
around the plant to enter the cells where they are required. To allow these substances to enter
the cells, plant cell membranes are selectively permeable. Let’s break down this key term to
find out what it means.
The word “permeable” derives from
the Latin word which means pass through, describing how something that is permeable
allows other substances to pass through it. This is essential in most plant
cells, as substances such as water, sugars, and mineral ions need to be able to move
into and out of the plant cells so that they can carry out their vital
functions.
The word “selectively” describes
how a plant cell can be fairly picky about what can enter it. Most plant cell membranes are able
to differentiate between different types of molecules, only allowing certain
molecules into the cell depending on what that particular cell currently requires
and barring other molecules from passing into it.
This means that we now know what it
means for a plant cell membrane to be selectively permeable and so the correct
answer to this question. The correct answer is (B): the
membrane will only allow certain substances to move in or out of the cell.
