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Basic questions about cells..

Discussion of all aspects of cellular structure, physiology and communication.

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Basic questions about cells..

Postby MIA6 » Wed Nov 01, 2006 12:06 am

1. Do 'Cells' include living cells and dead cells??? but what does it mean by living and dead? I read my book, it says virus sometimes are thought to be living cells since virus particles can reproduce. So what's the meaning of living cells? Are they just simply cells or....?
1. I think 'protoplasm' is the living substance inside the cell. 'Cell organelles' are the parts of the cell. Their definitions seem very similar, thus can you tell me their differences?
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Postby druid » Wed Nov 01, 2006 12:57 am

Virus cannot autonomously replicate. It's an obligate parasite of a cell.

Think of it as a large multimolecular complex which can use replicative enzymes of the cell to replicate itself. Imagine a protein capsule which contains a short DNA molecule. Capsule can attach to the cell and deliver DNA of the virus into the cell. DNA of virus will make replicative enzymes of the cell to 1) replicate it 2) to create capsule which this viral DNA codes for. Replicated viral DNAs and capsules will unite to form mature virus particles which will rupture the cell and come out to infect other cells. As you see a virus has no future without cells on which it parasitizes.

Think of cell as a autonomous self-replicating system, which is bounded from its environment by the cell membrane. It needs two things: 1) source of energy ( sunlight or chemical compounds ) 2) building blocks ( carbon atoms from CO2 or organic substances)
Cell itself knows how to use energy and building blocks to build its copy. To build copies is the main purpose of a cell. The set of chemical reactions by which a cell accomplish the task of building its copies is called metabolism. In contrast, virus has no enzymatic systems for energy /building blocks manipulations.

2. Protoplasm points to cell without its cell wall, that is protoplasm=cell membrane + cytoplasm. Cytoplasm is solvent, in which all cell components are suspended.

Cell organells are just inner compartments of the cell. Cell organells are separated from cell cytoplasm by a membrane. You can model the cell as a soap bubble, in which smaller bubbles float. These smaller bubbles are organells
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Postby druid » Wed Nov 01, 2006 1:24 am

Dead cell is one entropy of which is equal to entropy of environment.
Live cell can counteract entropy generation in such a way that net entropy change inside the cell is zero ( state of bacterial spores ) or negative ( replicating cell ).
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