Video Transcript
Which of the following best
compares the roles of cellulose and cutin in a plant cell? (A) Cellulose is the main component
of the cell wall that provides support and structure, and cutin primarily acts as a
waterproof barrier. (B) Cellulose is the main component
of the cell membrane that allows it to be flexible and permeable, and cutin
primarily acts as a strengthening material. Or (C) cutin is the main component
of the cell wall that provides support and structure, and cellulose is the main
component of the cell membrane that allows it to be flexible and permeable.
The question is asking us to
compare the roles of two substances that can be deposited into plant cells,
cellulose and cutin. To answer the question, let’s start
off by looking at some of the structures that we might find in a typical plant cell
before we observe the different substances that can be incorporated into them in
more detail.
Plant cells are eukaryotic, so they
contain a membrane-bound nucleus and some other membrane-bound organelles, like
chloroplasts. They also usually contain a
permanent vacuole that stores water, dissolved solutes, and enzymes. Each cell is surrounded by a cell
membrane that controls what substances can enter and leave the plant cell. This membrane is surrounded by a
cell wall. The main role of the cell wall is
to provide support and structure to the plant cell. And depending on the location and
function of the cell, the cell wall may have different substances incorporated into
it.
All plant cell walls contain an
insoluble polymer called cellulose. Cellulose is a very strong molecule
made of thousands of glucose molecules joined together that provides plant cell
walls with support and structure. Some plant cells have different
compounds incorporated into their cell walls, either to provide extra support or
additional functions. An example of a substance that can
be incorporated into certain plant cell walls, like those that form the waxy cuticle
on the surface of plant leaves, is called cutin.
Cutin makes cell walls waterproof,
which can be really helpful in certain cells to prevent excess water loss. The waxiness of the water-resistant
waxy cuticle on leaves also means that water droplets and any waterborne pathogens
that they may contain will usually drop right off the leaf so they cannot enter the
leaf cells to cause disease. Let’s take a look back at our
answer options to work out the correct answer.
Both options (B) and (C) state that
cellulose is the main component of plant cell membranes. This is incorrect, as we know that
cellulose is found in plant cell walls to offer support and structure to the cell
rather than in the cell membrane, which plays no role in structural support. So, we can eliminate both of these
options. This means that the correct
comparison of cellulose and cutin in a plant cell is option (A): cellulose is the
main component of the cell wall that provides support and structure, and cutin
primarily acts as a waterproof barrier.
