BIO-GEO CHEMICAL CYCLE OR NUTRIENT CYCLE Bio - Living organism Geo - Rock, Soil, Air, Water Chemical - Material or Nutrients Cycle - Path All the types of material required by ecosystem in addition of energy, are available continuously to system through recycling. Thus there is a constant exchange of materials between the living organism and their abiotic environment through the recyling of materials. This phenomenon is called Bio-geo chemical cycle. Note: Environment factors,e.g soil , moisture, ph, temperature etc, regulate the release of nutrients into the atmosphere. Biochemical cycle The following types of cycle are found in an ecosystem. (i) Gaseous Cycle - C, H, N. O cycles. Reservoir is in the atmosphere (air) or in Hydrosphere(water). Sedimentary cycle - P. S, Ca cycles reservoirs are in earth's crust (lithosphere). Note : In these cycles, the bulk material remains in the inactive reservoir on earth crust like sediment of sea, or water
FUNCTIONS OF LIVER
Liver is known as biological and chemical factory of the body.
Liver converts ammonia (more toxic) into urea (less toxic). Most of the biochemical functions of the body are done by the liver.
1) Secretion and synthesis of bile - This is the main function of liver. Bile is yellowish-green, alkaline fluid.In bile juice, bile salts, sodium bicarbonate, glycocholate, taurocholate, bile pigments, cholesterol,Lecithin etc. are present.
2) Carbohydrate Metabolism. The main centre of carbohydrate metabolism is liver.Following steps are related with carbohydrate metabolism-
Glycogenesis. The conversion and storage of extra amount of glucose into glycogen from the digedf food is called glycogenesis. The main stored food in the liver is glycogen,
Glycogenolysis- The conversion of glycogen into glucose again when glucose level in blood falls down is calledglycogenolysis.
Gluconeogenesis- At the time of need, liver converts non-carbohydrate compounds le.g Amino acid(.fatty acids) into glucose. This conversion is called gluconeogenesis. This is the neo-formative process of glucose
Gluconeogenesis : Synthesis of glycogen from lactic acid (which comes from muscles) is called glyconeogenesis.
3). Storage of fats-Liver stores fats in a small amount. Hepatic cells play an important role in fat metabolism.
The storage of fat increases in the liver of alcohol addict persons (Fatty liver). This stored fat decreases the activity of liver. The damage of liver due to alcohol intake is called alcoholic liver cirrhosis
4) Deamination and Urea formation-Deamination of amino acids is mainly done by liver (Amino acid → NH³)
Liver converts ammonia (more toxic) into urea (less toxic) through ornithine cycle.
5). Purification of blood- Kupffer cells of liver and splenocytes of spleen are the phagocytic cells, helps in phagocytosis of dead blood cells and bacteria from the blood.
6). Synthesis of plasma proteins- Many types of proteins are present in blood plasma. All the blood proteinse except Gamma-globulins are synthesized in the liver. Chemically antibodies are gamma globulins formed by lymphocytes prothrombin and fibrinogen proteins are also formed in hepatic cells. These help in blood clotting Factors I, II, V, VII, IX and X are formed in liver, which are responsible for blood clotting
7) Synthesis of heparin-Heparin is a natural anticoagulant (mucopolysaccharide).
Some heparin is also formed by basophils (granulated WBC) and mast cells.
8).Synthesis of Vitamin-A- The liver changes ß-carotene into vitamin-A B-carotene is a photosynthetic pigment which is obtain from yellow part of fruits. It is abundantly found in carrot.
9) Liver stores vitamins A,D,E,K,B¹²
10) Storage of minerals- Liver stores iron, copper, zinc, cobalt,molybdenum etc. Liver is a good source of iron.
11). Detoxification. The conversion of toxic substances into non-toxic substance is done by liver. The toxic substances are formed by metabolic activities of the body, e.g. Prussic acid is converted into Potassium sulfocynide(it is a non-toxic salt) by the liver.
12). Yolk synthesis (=Vitellogenesis) Most of the yolk is synthesised in liver
13) Haemopoiesis- The formation of blood cells is called haemopoesis. In embryonic stage R.BC and WBC are formed by liver.
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