00:01
Okay, let's talk about partitioning
and why we want to have
membrane structures within the cell.
00:08
So, cell membrane
and other membranes within the cell.
00:13
Let's first start by
talking about the cell membrane,
because this is probably the most
important.
00:17
Because it separates inside
the cell from outside the cell.
00:20
And why this is so important
if we talked about homeostasis
and maintaining the internal
environment within the cell,
we need to have some sort of
separation mechanism
to keep that inside and
separate that from outside.
00:37
However, each portion of the cell
or its organelles
will have various membranes
associated with them.
00:43
The endoplasmic reticulum is one.
00:45
And in this endoplasmic reticulum,
which could be rough or smooth,
is oftentimes where protein
synthesis is taking place.
00:52
This is also where you could
be packaging
some of the cell secretions
that may occur.
00:57
The Golgi complex
is kind of an extension
of the endoplasmic reticulum
where further
processing takes place.
01:05
And eventually you'll get some
budding of various vesicles.
01:08
And that will be what our
secretion mechanisms will be.
01:12
We also have various smaller
cellular structures
such as lysosomes, and peroxisomes.
01:18
These are located close to the
cell membrane just on the inside.
01:23
Lysosomes are complex organelles
and perform multiple functions,
including enzymatic digesting
organic material such as endocytosed
bacteria and worn -out cell components
by using more
than 60 hydrophilic enzymes.
01:37
They also perform cell membrane repairs
and are important in nutrient sensing,
metabolic adaptation,
organellar crosstalk, and aging.
01:45
The interior is kept acidic
at a pH of approximately 5,
which is a safety feature for the cell
because if the lysosomes were to break
open and release their contents,
the enzymes would not be efficient
at the near neutral
cytosolic of pH 7.2.
02:01
Peroxisomes are also complex organelles
that are involved in the biosynthesis
of membrane phospholipids,
fatty acid β-oxidation,
photorespiration, and the synthesis
of signaling molecules.
02:14
Peroxisomes also have roles
in stress responses,
reactive oxygen species metabolism,
üand appear to play a role in immunity.
02:22
The mitochondrial membrane
is the final kind of
organelle structure membrane
that we'll talk about.
02:29
It's a little bit more specialized.
02:31
In fact, it has a dual
membrane structure.
02:33
And so the first portion
of the membrane
allows for some things
to move in and out.
02:38
But then you have a second
membrane structure that is more
well separate the structures
to a little bit greater degree.
02:46
And this will be important
for such things as
oxidative phosphorylation and
production of energy
within the cell.
02:54
The nuclear envelope is another
kind of partition that we have.
02:58
It is not exactly like the other
cell membrane structures.
03:02
It has some larger pores in it that
allow for some molecules
to move in and out.
03:06
And that is helpful for
signaling and trafficking.
03:12
The final thing that we have
is a vesicle membrane.
03:15
And these vesicles usually
are butted off
from things like
the Golgi apparatus,
and will eventually dock
and fuse into the cell membrane
spilling its contents out into
the extracellular environment.
03:30
Okay, so now let's
talk a little bit about,
Why in the world do you
have partitions anyway?
And I think the best way
to think about
why partitioning things within
a cell is think about
your own apartment
or your own house.
03:42
Why do you have walls within your
particular apartment or house?
And why would that be important?
Or how is that sometimes helpful?
So why have these partitions?
Well, I think this
basically occurs often
when you want to do a specific
task within a certain room.
04:01
For example, cooking.
04:02
Sometimes it's advantageous
to cook within one room
and keep that separate
from the rest of the house.
04:08
Maybe you're making something that
has a certain aroma or smell to it
that you want to keep
within that room.
04:14
Or maybe you have certain tasks
that you want to do
at other parts
of the house or apartment
such as sleeping.
04:20
But yet you have an apartment mate,
or you have another person
that's living with you.
04:25
That person is not ready to go to
bed yet.
04:28
So by partitioning out that
it's easier to have
one function occurring
such as sleeping.
04:35
So how are these particular
partitions constructed?
Well, you're going to have
an inner wall and outer walls.
04:42
And as you know, usually
you have thicker outer walls,
then you will have inner walls.
04:48
But what are these
particular membranes made of?
So we'll spend a couple
of minutes talking about,
How they're specifically made up?
What their sizes are?
And how that structure
affects its function?