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Offline SaraMarie

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Why do some cells have more mitochondria ?
« on: 19/01/2004 17:39:13 »
Please explain why some eukaryotic cells may contain more mitochondria than other kinds of eukaryotic cells.


 

Offline Ylide

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Re: Why do some cells have more mitochondria ?
« Reply #1 on: 20/01/2004 00:42:43 »
Do you mean within the same organism?  Or do you mean why some single celled Eukaryotes might have more mitochondria?

Either way, think about what purpose the mitochondria serves and there is your answer...

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Offline cuso4

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Re: Why do some cells have more mitochondria ?
« Reply #2 on: 20/01/2004 09:05:02 »
Eukaryotes carry out more complicated chemical reactions processes and therefore need more energy. But like cannabinoid said, you need to be more specific.

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Offline chris

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Re: Why do some cells have more mitochondria ?
« Reply #3 on: 20/01/2004 11:55:23 »
Careful Angel - only eukaryotes have mitochondria ! According to the endosymbiont theory, at some time in the distant past a eukaryotic cell and a prokaryotic cell formed a mutually beneficial relationship whereby the prokaryote took up residence within the eukaryote. In return for the metabolic support and protection offered by the eukaryotic environment, the prokaryote provided efficient oxidative metabolism.

But to address the original question, why do some cells have more mitochondria than others, the simple answer is that their mitochondrial count is in direct proportion to the metabolic / energy requirements of the cell, since mitochondria are essentially microscopic cellular power stations.

Metabolically inert cells, like the shwann cells that form a myeline sheath around a nerve, contain very few mitochondria. In contrast, highly metabolically active cells, live hepatocytes (liver cells) or myocytes (muscles cells) contain large numbers of mitochondria. As a rule of thumb, the greater the energy demands of a cell, the greater the number of mitochondria it will contain.

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Offline cuso4

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Re: Why do some cells have more mitochondria ?
« Reply #4 on: 21/01/2004 11:07:27 »
Thanks Chris for correcting me. Yeah, I remember my teacher told me that mitochondria could have been a separate organism themselves as they have their own DNA and ribosomes.

Angel

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« Last Edit: 22/01/2004 11:00:24 by cuso4 »
 

Offline chris

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Re: Why do some cells have more mitochondria ?
« Reply #5 on: 21/01/2004 16:56:21 »
Yes, correct, and mitochondria are also the same size as your average bacterium, and their chromosome is circularised, like a bacterial chromosome.

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Offline Ylide

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Re: Why do some cells have more mitochondria ?
« Reply #6 on: 22/01/2004 07:48:07 »
And in the same vein, chloroplasts in photosynthetic plants are remarkably similar to algae.  These two tidbits are one of the main theories in evolution, that modern eukaryotic cells evolved from a symbiotic relationship between primitive bacteria/algae and the first protists.  Bacteria-based cells went on to form animal-like creatures and algae-based cells went on to form plant-like creatures.

The advantage for doing so was that the larger cell gained a valuable source of energy production.  Only glucolysis takes place in the cytoplasm, the remaining stages of respiration take place in the mitochondria.  (I don't know that plants partake in glucolysis, but most of their energy is regardless produced in the chloroplasts)  The bacteria/algae gained protection and greater motility, I suppose....as well as a larger genome from which to spring forth.

I can't remember the exact name of this theory, unfortunately.



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Offline chris

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Re: Why do some cells have more mitochondria ?
« Reply #7 on: 22/01/2004 11:13:25 »
Plants have mitochondria too. The chloroplasts are the sites of photosynthesis where electromagnetic energy drives the production of sugar (glucose) from carbon dioxide and water.

This sugar is consumed by cytoplasmic glycolysis and subsequent Kreb's Cycle / Oxidative Phosphorylation which occurs in mitochondria.

Chris

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Re: Why do some cells have more mitochondria ?
« Reply #7 on: 22/01/2004 11:13:25 »

 

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