Differences b/t Prokaryores, Eukaryotes, and Viruses

[TheGuy2000]

I always get tripped up on these questions about which organelles they have/ don't. Prokaryotes lack a nucleus, membrane bound organelles, and viruses have DNA or RNA but not both? Could someone help give a more definitive list? Quju or anyone who knows this stuff help!!!

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[totalcommand]

I always get tripped up on these questions about which organelles they have/ don't. Prokaryotes lack a nucleus, membrane bound organelles, and viruses have DNA or RNA but not both? Could someone help give a more definitive list? Quju or anyone who knows this stuff help!!!

Prokaryotes do not have membrane bound organelles. But they still have Ribosomes (really just rRNA-protein complexes with no membrane).

This means that they do not have a nucleus (chromosome is circular and lies in the cytosol - the area called "nucleoid"), mitochondria (respiration takes place in the cytoplasm), chloroplast, etc.

In other words, the only things they have similar to eukaryotes is a plasma membrane, cytosol, and (smaller) ribosomes. In addition, they have a cell wall and flagella, while eukaryotes do not.

Eukaryotes have the membrane bound organelles, which you should be able to find in a book.

Viruses only have DNA or RNA, not both, and have a protein coat/capsule. Sometimes they will carry enzymes with them inside the coat. Sometimes, (eukaryotic viruses) the protein capsule itself will be bound by a lipid bilayer stolen from host cells.

Recap:

Eukaryote = everything but cell wall
Prokaryote = Eukaryote minus membrane bound organelles, has cell wall and flagella

Virus = RNA/DNA inside a protein coat in its most basic form

 

[rs76]

Prokaryotes do not have membrane bound organelles. But they still have Ribosomes (really just rRNA-protein complexes with no membrane).

This means that they do not have a nucleus (chromosome is circular and lies in the cytosol - the area called "nucleoid"), mitochondria (respiration takes place in the cytoplasm), chloroplast, etc.

In other words, the only things they have similar to eukaryotes is a plasma membrane, cytosol, and (smaller) ribosomes. In addition, they have a cell wall and flagella, while eukaryotes do not.

Eukaryotes have the membrane bound organelles, which you should be able to find in a book.

Viruses only have DNA or RNA, not both, and have a protein coat/capsule. Sometimes they will carry enzymes with them inside the coat. Sometimes, (eukaryotic viruses) the protein capsule itself will be bound by a lipid bilayer stolen from host cells.

Recap:

Eukaryote = everything but cell wall
Prokaryote = Eukaryote minus membrane bound organelles, has cell wall and flagella

Virus = RNA/DNA inside a protein coat in its most basic form

Where is tRNA synethised. I read that it wasnt synthesized in the nucleolus?

 

[totalcommand]

Where is tRNA synethised. I read that it wasnt synthesized in the nucleolus?

It's not the nucleolus, but I can't remember the name of the place though...it's not on the mcat.

edit: people aren't sure - http://www.genesdev.org/cgi/content/full/12/16/2463, as of 1998.

 

[LT2]

be careful, some eukaryotic cells (ie plant, fungi) DO have cell walls. granted they are different than prokaryotic cell walls but they do have them. cell walls in prokaryotes contain peptidoglycan while in plant cells they contain cellulose and in fungi they contain chitin.

also, to build on bacteria lacking mitochondria, think of bacteria as little mitochondria. i hope that makes sense.

viruses are non-living. they do not have ribosomes, and their genomes can be (double or single stranded) RNA or DNA. they are obligate intracellular parasites meaning they can not survive without a host.