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The mysterious journey of an animal after death: How does the decomposition process begin?
Animal decomposition is an immediate and complex biochemical process that begins immediately after an animal dies, with the destruction of soft tissues, ultimately leaving behind skeletons. In this process, chemical decomposition plays an important role, involving the gradual decomposition of soft tissues, and includes two major processes: autolysis and putrefaction of cells and tissues. How do these processes unfold, and what mysteries are hidden?
The decomposition process includes the decomposition of proteins, carbohydrates, lipids, nucleic acids and bones, which is a multi-level biochemical activity.
Protein degradation
Proteins make up a variety of different tissues in the animal body, which can be divided into soft tissues and hard tissues. Therefore, protein degradation is not uniform during the breakdown process.
Proteolysis
Proteolysis is the process of breaking down proteins. This process is affected by humidity, temperature and bacteria. In early stages, soft tissue proteins begin to degrade, while in later stages, more putrefactive tissue proteins are degraded.
In the early stages of decomposition, proteins in the intestines and pancreas, and protein indicators in the brain, liver, and kidneys will be decomposed first.
The release of nitrogen
Nitrogen is an amino acid component that is released through the process of deamination, usually in the form of ammonia. If the body is on or in the soil, these nitrogen molecules may be used by plants or microorganisms, become nitrates, or accumulate in the soil.
The nitrogen content in the soil is thought to aid the growth of nearby plants.
Degradation of carbohydrates
Early in the decomposition process, carbohydrates are degraded by microorganisms, starting with glycogen and a series of carbohydrate reactions. These sugars can ultimately be converted into carbon dioxide and water, or intermediate products such as organic acids and alcohols, under different environmental conditions.
In an aerobic state, fungi and bacteria will convert sugar into a variety of organic acids; in an anoxic environment, lactic acid, butyric acid, and acetic acid may be produced.
Degradation of lipids
Lipids are mainly found in adipose tissue, which contains approximately 60-85% lipids, of which 90-99% are triglycerides. The hydrolysis process of lipids is carried out by lipase, and with the post-mortem changes, these lipids are converted into a mixture of saturated and unsaturated fatty acids.
Degradation of fatty acids
Due to the lack of oxygen, anaerobic bacteria will preferentially dominate the degradation of fatty acids, which will promote the hydrogenation of unsaturated bonds. On the other hand, in an aerobic environment, fatty acids undergo oxidation reactions to produce products such as peroxides, aldehydes, and ketones.
The degradation products of lipids end up being very complex and varied, and these compounds continue to interact with their surrounding environment over time.
Degradation of nucleic acids
The degradation of nucleic acids produces nitrogenous bases, phosphates and sugars, which are then further broken down by the degradation pathways of other macromolecules.
Degradation of bone tissue
Bone tissue is composed of multiple components, including rich collagen and the mineral hydroxyapatite. Even after soft tissue has completely degraded, bone may still survive because of its structure. However, the bone degradation process is affected by a variety of factors, including moisture, soil type, and microbial, plant and animal activity.
Moisture will accelerate the degradation of bone tissue and has a significant impact on the pH of the soil.
However, during these complex decomposition processes, what kind of microscopic life is silently performing these mysterious tasks, allowing our environment to contribute back to the cycle of nature?
