Electron micrographs show us that mitochondria do contain many
Can you figure out what all this membrane surface must mean?
contained between the membranous plates?
Electron micrograph pictures
show that surrounding the folds is a fuzzy background. How can
we know what is there?
Mitochondria can be separated from cells by gently crushing
the cells and then spinning the suspension in a
test tube at high speed.
Because of their size and weight, mitochondria settle out in a
"Pure" mitochondria can be obtained by using a
pipette to suck out this layer.
- Then, filtering out
the membranes that make up the folds reveals that the rest
of the material contains many chemicals, including DNA. This
is called "maternal" DNA because it is inherited
only from your mother. The purpose of this DNA is to direct
the formation of new mitochondria when cells divide.
Mitochondria make a lot of energy, and the
chemical reactions also make a by-product of free-radicals.
These radicals are highly reactive and toxic chemicals that can poison cells, which is especially serious for RNA and
DNA. The DNA inside the mitochondria is an easy target, because
it is already inside the mitochondria where the free radicals
are being generated. The DNA inside mitochondria are genes
and they are inherited only from the mother. Free radical poisoning is a special problem
in nerve cells. Because nerve cells survive so long, the damaging
effects in them can accumulate over time. This toxic effect may
cause such brain diseases as Parkinson's Disease and
Huntington's Disease. Prevention of free radical damage can
perhaps be reduced by taking "anti-oxidant" vitamins, such as
Vitamin C and Vitamin E.
A discovery made in the
year 2000 revealed that certain proteins that are trapped inside
these membranes can trigger cell death once they are untrapped.
During certain stages of development and during aging,
mitochondrial membranes break down to release these deadly
poisons. This process is called "programmed cell death."
Does this suggest that life span is dictated by genes from the
mother? We are not sure because scientists have not looked into
How do the genes in
mitochondria differ from the genes in the cell nucleus?
A. They come only from the
B. They have a different kind of nucleic acid
C. They are regulated the same way.
D. They control the same functions as genes in the nucleus