BISMILLAHI RAHMANI RAHIM

Robert Lue: You often think of mitochondria as simply floating around
inside the cytosol.
But, in fact, most mitochondria move in defined paths
along the cell's microtubule network.
Microtubule structure is remarkably dynamic
and is constantly being remodeled.
This remodeling of the network is important for the cell's ability
to respond to metabolic changes or metabolic stress.
Depending on these metabolic needs, mitochondria
can be redistributed in the cell via this dynamic network.
Mitochondria are also quasi independent from the rest of the cell.
Rather than relying on the smooth ER for lipid synthesis, for example,
mitochondria can make their own lipids, which
is a necessary process for the division of mitochondria.
The spatial distribution of mitochondria within a cell
can be quite distinctive from one cell type to another.
In neurons, for example, there's a specialized area
called the axon hillock, which is enriched in channels and transporters,
all of which require ATP.
Thus there is also an increased concentration of mitochondria
in that region of the neuron.
Now that we have introduced the components of the mitochondrion,
we will be able to appreciate just how intimately its overall structure is
linked to its function as the powerhouse of the cell.
As we will see, the double membrane structure of the mitochondrion
is precisely what enables it to harness chemical energy in the form of ATP.
Let's begin by looking at a very important series of chemical reactions
that happen within the mitochondrial matrix, that innermost volume
of the mitochondrion.
As you will see in the next lesson, the food we eat
is digested into simple sugar molecules called glucose.
Following a meal or a snack, high concentrations of glucose
produced by digestion float through our bloodstream
until the glucose in the blood is absorbed by our cells.
Cells begin to break down glucose to harness energy
in the cytosol through a series of chemical reactions called glycolysis.
The product of glycolysis is pyruvate, and the breakdown
of a single glucose molecule into two pyruvate molecules
generates a small amount of ATP.
The pyruvate that was produced by glycolysis, on the other hand,
is transported into the matrix of the mitochondrion, where
it can be broken down more fully to generate many more ATP molecules
than is produced by glycolysis.