Why do some cell organells have membranes and others not?

Question

In other words, what purpose does it serve to an organelle. Also, can you please give me some info on mitochondria? Thanks!!

Answer 1

Bacterial organelles are membrane-less and they are fairly (not to oversimplify) less complex than Eukaryotes. All eukaryotes and multicellular organisms have membrane bound organelles. They separate cellular activity. For ex. the nucleus v. the nucleoid. Where there is no nuclear membrane transcription and translation of genomic data can occur together in the cytoplasm. This is ok if your genome is simple. If it is more complex with many orf's this can become a problem. Basically, it keeps the cell organized!

Mitochondria are (of course) ATP producing organelles. The folds in the cristae provide surface area for this formation to occur. It happens via electron transport chain and extrusion of H+ atoms. They're pretty cool little buggers.

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Answer 2

I'm not entirely sure, but I believe that the organelles that have membranes actually used to be primitive cells on their own way back in the beginnings of life on earth. Over time, theses primitive cells grouped together a bit and created larger cells. The primitive cells kept their own membranes within the bounds of the larger cell's membrane. For example, I believe that organelles like mitochondria and chloroplasts existed on their own and eventually got absorbed into larger cells.
Mitochondria are the energy powerhouses of the cell. An interesting fact may be that mitochondria have their own DNA and that DNA is transferred to future generations through the mother.

Answer 3

Scientists believe that some organelles have membranes because they were a seperate "creature" at one point. Meaning, many many years ago, they could live independently from the cell, but then joined with other similar things and never lost their membranes.
Here is exactly what wikipedia.org says on the matter
"Organelles which have double-membranes and their own DNA are believed by many biologists of having originally come from incompletely consumed or invading prokaryotic cells, which were adopted as a part of the invaded cell through endosymbiosis."

Info on mitochondrion?
Here you go:
Mitochondria are responsible for converting organic material into energy (in the form ATP) in the process of cellular respiration. "Usually a cell has hundreds or thousands of mitochondria, which can occupy up to 25% of the cell's cytoplasm." They HAVE their own strands of DNA in them (unlike other organelles).

Here are the more specific tasks they do (straight from wikipedia)
"Apoptosis-programmed cell death
Glutamate-mediated excitotoxic neuronal injury
Cellular proliferation
Regulation of the cellular redox state
Heme synthesis
Steroid synthesis"
"Some mitochondrial functions are performed only in specific types of cells. For example, mitochondria in liver cells contain enzymes that allow them to detoxify ammonia, a waste product of protein metabolism. A mutation in the genes regulating any of these functions can result in mitochondrial diseases."

For now, just remember that mitochondrion are the "power plants" of cells!

Answer 4

a cell membrane protects the cell.in animal cells,its the thing behind the cell wall,but in animal cells,it is the outer part of the cell,since animal cells dont have a cell wall.

the mithochondria are the rod-shaped things that produce most of the energy a cell needs to carry out it's function.

Answer 5

b is the respond. Prokaryotic species are the two archibacteries or eubacteries. those 2 types have cellular membrane although they membrane systems selection from one yet another.