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Decomposition of soft tissues: Why are some proteins more durable than others?
The decomposition process of an animal begins immediately after death and involves primarily the destruction of soft tissues, ultimately leaving behind skeletal remains. This chemical process is extremely complex and involves the breakdown of multiple molecules in the body, including proteins, fats, carbohydrates, nucleic acids and bones, and takes place in a step-by-step breakdown process.
Protein degradationThe human body is approximately 64% water, 20% protein, 10% fat, 1% carbohydrates, and 5% minerals.
Proteins make up many different tissues in the human body, which can be divided into soft tissue and hard tissue proteins. Because of this variation, proteins in the body are not degraded at a uniform rate.
Protein hydrolysis
Proteolysis is a process that breaks down proteins and is affected by humidity, temperature and bacteria. During the hydrolysis process, different proteins are degraded at different stages. In the early stages, soft tissue proteins are the main degraded proteins, including epithelial cells of the intestines and pancreas, as well as proteins of the brain, liver and kidneys.
Later in the decomposition process, more resilient proteins are gradually degraded, including reticulin and collagen, the latter of which survives even longer than the former.
Hydrolysis products
Usually, protein hydrolysis produces the following products:
- Protein solution
- Small peptides
- Peptide
- Amino Acids
Continued protein hydrolysis produces phenolic substances, as well as gases such as carbon dioxide, hydrogen sulfide, ammonia and methane.
Nitrogen and phosphorus release
Nitrogen is a component of amino acids and is released during deamination, usually in the form of ammonia. Ammonia in the environment can be used by plants or microorganisms, or converted to nitrates, and if the body is on or in the soil, ammonia may accumulate. This allows the presence of nitrogen in the soil to promote the growth of nearby plants.
P release also depends on the pH of the soil environment and is usually present in the form of insoluble inorganic complexes combined with iron, calcium, magnesium and aluminum.
Carbohydrate degradation
In the early stages of decomposition, microorganisms break down carbohydrates. The process begins with the breakdown of glycogen into glucose monomers. Depending on the availability of oxygen in the environment, sugars can be broken down completely into carbon dioxide and water, or incompletely into various organic acids and alcohols. Both pathways may occur simultaneously, either aerobic or anaerobic.
Degradation of lipids
Lipids are mainly found in adipose tissue, about 60-85% of which are lipids, mainly triglycerides. Shortly after death, neutral lipids are hydrolyzed by lipase to form free fatty acids. The degradation pathways of these fatty acids will depend on the availability of oxygen and may occur via both anaerobic and aerobic pathways.
Degradation of Nucleic Acids
Nucleic acid breakdown produces nitrogen bases, phosphates, and sugars, which are further processed through other macromolecular degradation pathways.
Degradation of bones
Bone is a composite tissue composed of proteins, minerals, and other organic substances. The degradation of bone is called mineralization, which involves a combination of bacterial and chemical factors. As the environment around the bones changes, these tissues will be broken down and eventually absorbed into the environment.
The rate at which bone degrades is affected by the surrounding environment, including water, soil type, temperature, and pH. The activity of microorganisms can also influence this process.
Faced with the end of life and the decomposition of the body, can we think more deeply about the ecological balance and the significance of the continuation of life brought about by this natural process?
