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Epinephrine binds to a beta-adrenergic receptor in the cell membrane of the adipocyte, which causes cAMP to be generated inside the cell. The cAMP activates a protein kinase, which phosphorylates and thus, in turn, activates a hormone-sensitive lipase in the fat cell. This lipase cleaves free fatty acids from their attachment to glycerol in the ...
Lipid metabolism is often considered the digestion and absorption process of dietary fat; however, there are two sources of fats that organisms can use to obtain energy: from consumed dietary fats and from stored fat. [5] Vertebrates (including humans) use both sources of fat to produce energy for organs such as the heart to function. [6]
A young adult human's fat stores average between about 15–20 kg (33–44 lb), but varies greatly depending on age, sex, and individual disposition. [10] In contrast, the human body stores only about 400 g (0.9 lb) of glycogen , of which 300 g (0.7 lb) is locked inside the skeletal muscles and is unavailable to the body as a whole.
Fat cells may also be broken down for that reason if the brain's needs ever outweigh the body's. Triglycerides cannot pass through cell membranes freely. Special enzymes on the walls of blood vessels called lipoprotein lipases must break down triglycerides into free fatty acids and glycerol.
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 ...
Ketone bodies are produced mainly in the mitochondria of liver cells, and synthesis can occur in response to an unavailability of blood glucose, such as during fasting. [4] Other cells, e.g. human astrocytes, are capable of carrying out ketogenesis, but they are not as effective at doing so. [6] Ketogenesis occurs constantly in a healthy ...
The main physiological requirement for ω−6 fatty acids is attributed to arachidonic acid, which is the major precursor of prostaglandins, leukotrienes that play a vital role in cell signaling, and an endogenous cannabinoid anandamide. [17] Metabolites from the ω−3 pathway, mainly from eicosapentaenoic acid, are mostly inactive. [18]
An uncoupling protein known as thermogenin is expressed in some cell types and is a channel that can transport protons. When this protein is active in the inner membrane it short circuits the coupling between the electron transport chain and ATP synthesis. The potential energy from the proton gradient is not used to make ATP but generates heat.