Metabolism is composed of reaction sequences termed as metabolic pathways. The changes at each step in a metabolic pathway are regulated in order to maintain the stability and survival of the organism. Mainly there are four ways of controlling metabolism. Such one important way of controlling metabolism at cellular level is compartmentation.
When considering a eukaryotic
cell; it’s composed of many different compartments known as sub cellular
organelles in contrast to a prokaryotic cell. Each organelle contributes a
specific metabolic function with different enzymatic activities under different
conditions. These metabolic pathways needed to be interconnected to maintain
the metabolism. Therefore compartmentation allows the distribution of
metabolites and enzymes between the membranes bounded organelles. It’s the
method that enables the cell to obtain different metabolic activities at the
same time for more energy efficiency. For an example, glycolysis occurs in the
cytoplasm and provides the mitochondria substrates such as pyruvates from
carbohydrate oxidation. TCA cycle occurs within the mitochondrion matrix while
oxidative phosphorylation occurs in mitochondria inner membrane. However,
altogether all these three processes are included in one metabolism called ‘cell
respiration’. Enzymes of each process are found where the processes take place.
Fat metabolism is
another one good example for compartmentation. Fatty acids synthesis takes
place in cytoplasm. Cytoplasm contains the required enzymes for the anabolism
of fatty acid synthesis. But these fatty acids are degregaded in mitochondria
supplying Acetyl Co A for TCA cycle. Mitochondria also contain the enzymes
require for the catabolism of fat.
RNA polymerase allows
RNA synthesis by using a template of DNA strand. It catalyzes the synthesis of RNA.
RNA synthesis takes place in nucleus. DNA transcription also occurs in nucleus.
Therefore both the RNA polymerase and DNA templates are available, so that the
RNA synthesis is favorable. When considering protein synthesis, all the organelles
used for it are close to one another. The nucleolus makes ribosome which synthesizes
proteins. Endoplasmic reticulum is near the nucleus to receive Ribosomes and
synthesized proteins. The Golgi apparatus is also near the endoplasmic
reticulum for storing, packaging and distribution. Therefore all the activities
within a cell are cooperated with one another.
Hence,
compartmentation helps metabolic controlling by maintaining substrates,
regulators and enzymes in separate locations with only favoured access between
them.
