Senescence
The biogerontology (Greek bios " life " Geron " old man " logos " doctrine ") is the branch of developmental biology that deals with the study of the causes of biological aging ( engl. aging, aging AE ) and their consequences, senescence ( lat = senescere, old be ') in individual cells ( Biochemistry) and organisms ( physiology ) busy.
Senescence includes the generally non-reversible processes that inevitably lead to the death of an organism, its organs or individual cells. Aging is a major cause for the death of an organism, next play senescence phenomena in the normal catabolism (cell breakdown) a role. Discussed are more than 300 different theories of aging.
The biogerontology is an important basis for the discipline - especially in human medicine oriented - Gerontology. In contrast, the geriatrics deals with the biological effects of aging, so the various associated with the diseases of old age ( the expressions infirmity and old age are in technical language rarely used). The corresponding field of veterinary medicine veterinary gerontology, the botany of the general plant physiology.
- 2.1 senescence in plants
Causes of aging
Primary causes
Primary aging, also called physiological aging is caused from the perspective of biology by cellular aging processes that occur in healthy organisms. The primary aging defined for an organism 's maximum achievable life span in humans at about 115 to 120 years. On the question of why organisms age, there are different answers. Of these aging theories to date, no scientifically comprehensive response was accepted. The theories can be divided into three biological approaches:
- Called wear theories, wear theories, even passive aging Energy consumption related theories of aging such as the CR hypothesis ( calorie reduction). Simply put: The more a living being - in relation to its body weight - eat, the shorter it lives.
Secondary causes
A condition for reading ( transcription) or the duplication of the stored information ( replication ), as well as for the repair of DNA damage are helicases, opening the DNA double helix. For example, subject to people who are ill with Werner's syndrome as a result of a defect in the WRN protein, a helicase, a rapid aging process.
Effects of aging
There are many causes of aging, a principal is probably attributed to the free radicals: The present in most cells, mitochondria use the inhaled oxygen to energy in the form of ATP to produce. 1 to 2 % of the oxygen, this process passes (see terminal oxidation ) but corrupted. The oxygen atoms leave the process with an unpaired electron in the last shell and are therefore extremely reactive. These oxygen atoms form the main group of free radicals, reactive oxygen species (ROS). If now take these particles to a different membrane proteins or other chromosomes, they can be damaged or even destroyed. Anti-oxidant (Vitamin A, C, E, uric acid, various enzymes ) are responsible for the capture of free radicals. Nevertheless, it is at present about 10,000 DNA lesions per cell per day in humans, but which may be repaired for the most part. This clearly shows that the effectiveness of the body's own repair mechanisms essentially decide on the life span of the individual, whose quality is in turn determined genetically. Free radicals are associated with various chronic diseases ( adult-onset diabetes, Parkinson's disease, Alzheimer's dementia).
Senescence in plants
In botany senescence phenomena include ( leaf fall in woody plants, death of aboveground plant parts with perennials and the like) to the normal growth process. Senescence can be controlled by phytohormones in plants. Cytokinins prevent aging processes, ethylene promotes this (eg, leaf senescence, abscission of leaves). This particular chronobiological relationships come into consideration.