Do different environments exist in a cell?

[hivesaeed4]

I read in a book concerning cell biology:

"Many enzymes are also greatly affected by the precise chemical environment around them."

I understand that enzymes are affected by their respective environments.

The book's sentence seems to indicate that different environments exist in the same cell (which then go on to affect enzymes in different ways).

Now since the interior of the cell is a fluid environment and that due to random thermal motion of the molecules everything in the cell is uniformly distributed throughout the cell so only one environment will exist in the cell. The environment present anywhere in a cell will exist everywhere else in the cell (except in the membrane bounded organelles).

So could someone tell me whether only one or different environments exist in a cell.

 

[aroc91]

Organelles are the only way to maintain different environments. It seems you've answered your own question.

 

[Pythagorean]

Now since the interior of the cell is a fluid environment and that due to random thermal motion of the molecules everything in the cell is uniformly distributed throughout the cell so only one environment will exist in the cell. The environment present anywhere in a cell will exist everywhere else in the cell (except in the membrane bounded organelles).

That would only be true in the long term if no change occurred and chemical equilibrium were allowed to be reached, but the reality is that in local regions of the cell, events can happen that raise a concentration of particular chemical species locally (for instance, IP3 releasing Ca from ER stores or ion channels opening near the membrane or ligand receptors starting g protein cascades near the membrane or a burst of recently expressed proteins being translated in the ER).

 

[Ygggdrasil]

Emerging research suggests that certain constricted regions of cells, for examples the spines containing post-synaptic terminals in neurons, can have distinct chemical microenvironments. These microenvironments mainly exist for calcium signaling because calcium is rapidly sequestered by various calcium-binding proteins and other processes so that calcium concentrations are only elevated near the channels that bring calcium into the cell.

For more information see the following perspective in Science:

Exquisitely local signaling provides robust, precise, and rapid communication in single cells. Nanometer-wide regions constitute the signaling conduit that separates interacting ion channels, organelles, and sensor and effector proteins. Such signaling domains are primary features of many systems, including those responsible for excitation-contraction coupling in the heart (1, 2), smooth muscle tone in the vasculature (3, 4), and Ca2+ signaling in neurons (5). These intimate pathways, also known as “fuzzy spaces” (1), “subspaces” (6), or “nanoscopic spaces,” permit efficient signaling with rapid and reliable information transfer, yet are too small to be seen with a standard optical microscope. Such superresolution domains may become experimentally visible with the implementation of optical superresolution microscopy (7–9). On page 597 in this issue, Sonkusare et al. (10) identify a specific and broadly important local signaling organization in small mesenteric arteries (~100 µm in diameter) that uses nano meter-wide communication regions to regulate local vascular blood flow.

http://www.sciencemag.org/content/336/6081/546.summary

 

[hivesaeed4]

Thanks guys. I get it now.

 

[Andy Resnick]

It's also worth mentioning that pH varies within a cell: the mitochondria have an interior pH significantly more acidic; the golgi apparatus has a pH gradient, and lysosomes are acidic as well.

 

[Darwin123]

I read in a book concerning cell biology:

Now since the interior of the cell is a fluid environment and that due to random thermal motion of the molecules everything in the cell is uniformly distributed throughout the cell so only one environment will exist in the cell. The environment present anywhere in a cell will exist everywhere else in the cell (except in the membrane bounded organelles).

So could someone tell me whether only one or different environments exist in a cell.

You gave the basic answer in your question. Membranes produce different environments in the cell. Even if there were no organelles, the cell membrane would cause the cell to be divided into different chemical environments. A molecule embedded in a cell membrane would be in a different environment then a similar molecule suspended in a liquid outside the cell membrane. A molecule in the lipid layer of a cell membrane would be in a different environment then the same molecule in a protein layer of the same membrane. A molecule in the outer protein layer of a cell membrane would be in a different environment then the same molecule in the inner protein layer of the cell membrane.
A eukaryote cell is divided into different organelles by cell membranes. Some molecules are suspended in the liquid. The liquid in one organelle is in a different environment then the liquid in another organelle. Bacterial cells are slightly different because they don't have organelles. However, there are features on the cell membranes of bacteria that provide different environments for molecules. However, there are fewer environments in a typical bacterial cell then there are in a typical eukaryote cell.
The chromosomes are made of histone protein molecules wrapped up in DNA molecules. DNA in one part of the chromosome is in a different environment then the DNA wrapped up in another part of the histone. Some of the so called epigenetic effects are dominated by the position of a DNA molecule relative to different parts of the histone.