Re: What exactly would happen if the mitochondria wasn't in the cell?

Dear Allison,

Very good question. 

Mitochondria (that’s the plural - "mitochondrion" is the singular) are 
often called the power plants of the cell. Without mitochondria, the amount 
of energy a cell can get from its favorite fuel, sugar (specifically, the 
kind of sugar molecule called "glucose"), would be about nine times lower 
than it is with mitochondria. When one molecule of glucose is completely 
broken down ("oxidized") by a cell into carbon dioxide and water, 36 
molecules of the special energy-containing molecule called ATP ("adenosine 
triphosphate") are formed. Out of those 36 molecules of ATP, 32 come from 
the mitochondria. Only four come from the more ancient biochemical pathway 
called "glycolysis", which means splitting sugar. The complete breakdown of 
sugar to make ATP involves a very complicated set of reactions that 
together go by the name of "oxidative phosphorylation", which basically 
means adding oxygen to molecules and using the energy from that to transfer 
the phosphorus needed to make ATP. 

What does that mean in practical terms? If your body cells had no 
mitochondria, you would have to eat and drink 9 times as much food to get 
the same amount of energy. So every day you could either eat 27 meals the 
same size as the ones you eat now, or you could just fill your plate 9 
times at each meal! Or, you would only be able to do one-ninth the amount 
of work that you do now. Actually, that wouldn’t even work, since a lot of 
the energy you make is used to keep your body temperature just where it 
belongs so that the rest of your body’s chemistry and functions keep 
working right. In other words, without mitochondria, life would be 
completely different, and a lot less interesting and dynamic - no running 
horses, no whales, no little swimming things in the ocean, no insects, 
flowers, ferns or trees. 

There are many interesting things to learn about biochemistry, cell 
biology, and evolution from studying mitochondria. Did you know that 
scientists now think that modern cells with mitochondria evolved from a 
partnership, or "symbiosis", between cells with a nucleus that could only 
carry out glycolysis and bacteria with no nucleus that could carry out 
oxidation of glucose? Mitochondria multiply in your cells in a way that’s 
not synchronized with the division of the cell. Also, they have their own 
genes in them - in mammals, a circle of DNA about 16,000 bases long - and 
they use a slightly different (simpler) "language" when translating the 
instructions contained in their DNA into proteins. But most of the hundreds 
of genes for proteins that the mitochondria use to oxidize fuel and make 
ATP are carried in the cell’s nucleus. These genes get copied into RNA in 
the nucleus, the RNA then gets translated into protein in the cytoplasm, 
and special parts of the protein act as labels tell the cell’s transport 
machinery to ship them to the mitochondria. And recently, there have been 
many studies that seem to say that the gradual loss of mitochondrial genes 
and function in the body are a major factor in aging. Interesting little 
power plants!

I hope this answers your question, and keep on wondering and asking 
questions.

Paul Odgren, Ph.D.
Cell Biology
University of Massachusetts Medical School
Worcester