What I want to do in this video is talk a little bit more
about the concept of an organelle.
And as you can see it contains the word organ,
and that's because the idea of an organelle
is related to the idea of an organ.
If you're talking about a human being,
if you're talking about me, I have a liver.
A liver is an organ.
I have lungs.
I have a heart.
These are substructures of Sal.
Similarly, an organelle is a substructure of the cell.
You could view it as almost an organ of the cell.
And actually let me be a little bit more particular there,
membrane-bound structure of cell.
So for example, let me draw a cell.
So that is my cell right over here.
We're already familiar with the idea of a nucleus.
A nucleus is a membrane-bound structure,
so it is an organelle, nucleus.
We've talked about the endoplasmic reticulum, which
is also a membrane-bound structure,
so it is also an organelle.
We have talked about the Golgi bodies.
Once again membrane-bound structures, so it
is also an organelle.
So that's a Golgi body right over there.
We have the endoplasmic reticulum right over there.
And by this definition even these small little vesicles,
these little membranes that are carrying things around,
even these vesicles could be considered to be organelles.
Vesicle.
And if you have really large vesicles,
or a bunch of these vesicles fused together,
you have these larger membrane-bound structures
called vacuoles, which could just be really viewed
as large vesicles or a bunch of vesicles fused together.
Vacuoles.
All of these things, these are all membrane-bound structures
inside the cell, and so these are all considered organelles.
Now some people are a little bit more particular.
When they really talk about organelles they say,
OK, we could say maybe membrane-bound structures,
but there are some organelles that are not
only membrane-bound, but they also have their own DNA.
For example, you have mitochondria,
which I will do in pink, which exist in most eukaryotes.
And this is really the energy-producing,
I guess you could say, the energy factory of the cell.
Let me draw it like this.
It has an inner and an outer membrane,
so that right over there is mitochondria.
It really takes sugars and is able to take that sugar
chemical energy and turn it into ATP, which I guess is still
a chemical energy but a more useful, or a more readily-used
form of energy.
Mitochondria.
In plants you have plastids.
And the most famous, or at least from our point of view
the most famous of these are chloroplasts
where photosynthesis takes place, where you're
taking light energy and turning that
into chemical energy in the form of sugars.
So this right over here, this is a chloroplast.
Let me go into much more detail with those
when we talk about photosynthesis.
So that right over there, a chloroplast,
which is a more particular form of a plastid.
So I just drew a chloroplast.
But that's a more particular form of a plastid.
It also has its own DNA.
And so mitochondria and plastids generally
are fascinating because it is believed,
because they have their own DNA and they can replicate
themselves, that it's believed that their ancestors were once
independent prokaryotes.
And at some point these independent prokaryotes
started to get together and into a membrane-bound structure
started to work together in symbiosis.
And that kind of collaborative of these prokaryotes working
together is believed to be the predecessor of, say,
many modern cells that contain these structures.
So it's a really fascinating window
into how these things actually might have formed.
But the big picture here that I just
want to make sure we understand, is that organelles, really,
it's generally viewed as any membrane-bound structure,
anything as simple as a vesicle, all the way to something that
has its own DNA, like mitochondria or plastids.