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Ketogenesis is the biochemical process through which organisms produce ketone bodies by breaking down fatty acids and ketogenic amino acids. [ 1 ] [ 2 ] The process supplies energy to certain organs, particularly the brain , heart and skeletal muscle , under specific scenarios including fasting , caloric restriction , sleep, [ 3 ] or others.
Ketone bodies are water-soluble molecules or compounds that contain the ketone groups produced from fatty acids by the liver (ketogenesis). [1] [2] Ketone bodies are readily transported into tissues outside the liver, where they are converted into acetyl-CoA (acetyl-Coenzyme A) – which then enters the citric acid cycle (Krebs cycle) and is oxidized for energy.
In the liver, muscles, and the kidney, this process occurs to provide glucose when necessary. [12] A single glucose molecule is cleaved from a branch of glycogen, and is transformed into glucose-1-phosphate during this process. [1] This molecule can then be converted to glucose-6-phosphate, an intermediate in the glycolysis pathway. [1]
Put another way, if the human body relied on carbohydrates to store energy, then a person would need to carry 31 kg (67.5 lb) of hydrated glycogen to have the energy equivalent to 4.6 kg (10 lb) of fat. [10] Hibernating animals provide a good example for utilization of fat reserves as fuel. For example, bears hibernate for about 7 months, and ...
Metabolism (/ m ə ˈ t æ b ə l ɪ z ə m /, from Greek: μεταβολή metabolē, "change") is the set of life-sustaining chemical reactions in organisms.The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the conversion of food to building blocks of proteins, lipids, nucleic acids, and some carbohydrates; and the ...
In general outline, photosynthesis is the opposite of cellular respiration: while photosynthesis is a process of reduction of carbon dioxide to carbohydrates, cellular respiration is the oxidation of carbohydrates or other nutrients to carbon dioxide. Nutrients used in cellular respiration include carbohydrates, amino acids and fatty acids.
In animals, the processes of alternating cycles of biochemical reactions of ATP synthesis and cleavage occur automatically. Moreover, the processes of alternating cycles of biochemical reactions at the levels of organs, systems and the whole organism, for example, respiration, heart contractions and others occur with different periods and ...
Starvation response in animals (including humans) is a set of adaptive biochemical and physiological changes, triggered by lack of food or extreme weight loss, in which the body seeks to conserve energy by reducing metabolic rate and/or non-resting energy expenditure to prolong survival and preserve body fat and lean mass.