Compartmentation of metabolic pathways
Compartmentation of individual metabolic pathways is an important element of metabolism regulation. The division of the cell into separate compartments allows opposing metabolic pathways to take place in the cell at the same time. It also simplifies the regulation of some lanes. For example, the regulation of β-oxidation is based on this principle, where the rate of fatty acid oxidation is dependent on the entry of fatty acids into the mitochondrion.
| Organelle | Metabolic pathways |
|---|---|
| Cytosol | Glycolysis, part of gluconeogenesis, pentose cycle, glycogen metabolism
Synthesis of fatty acids Synthesis of non-essential AMK, transamination, part of the ureosynthetic cycle Metabolism of purines and pyrimidines Part of heme synthesis |
| Mitochondria | The citrate cycle and the respiratory chain
Beginning of gluconeogenesis β-oxidation of fatty acids Part of the urosynthetic cycle Start and end of heme synthesis |
| Rough endoplasmic reticulum | Proteosynthesis (on ribosomes)
α- and ω-oxidation of fatty acids, transformation of xenobiotics Synthesis of TAG and phospholipids Cholesterol synthesis, steroid reduction |
| Golgi apparatus | Glycosylation and hydroxylation of proteins |
| Lysosomes | Hydrolases, acid phosphatase, lysozyme |
| Peroxisomes | Degradation of long-chain fatty acids |
Transport of metabolites between compartments[edit | edit source]
Metabolites are substances that are often soluble in water and therefore cannot pass through the membrane on their own. This applies both to the cytoplasmic membrane and to the intracellular membranes delimiting individual compartments. Therefore, transport mechanisms are needed. Most metabolites have their carriers in the membranes – pyruvate, citrate, malate easily pass through the membrane. Considering that metabolites are often associated with large molecules, it would be useless to transport whole molecules and thus only their parts are transported.
Three transport systems are particularly important in metabolism:
Compartmentation also complicates the onset of gluconeogenesis. The enzyme pyruvate dehydrogenase is only present in mitochondria. The resulting oxalacelate cannot pass through the membrane, so it must be transaminated to aspartate or reduced to malate, which pass through the membrane and are converted back in the cytosol.
Links[edit | edit source]
Related articles[edit | edit source]
References[edit | edit source]
- DUŠKA, František – TRNKA, Jan. Biochemistry in context Part I - basics of energy metabolism. 1st edition edition. Karolinum, 2006. ISBN 80-246-1116-3.
- KVASNICOVÁ, Vladimíra. Regulation of metabolism at the cellular level [online]. ©2009. [cit. 2010-10-27]. <http://old.lf3.cuni.cz/chemie/cesky/kruhy/1_rocnik/kruh_8/24b_regulace_metabolismu_vk.ppt>.
