Energy and Metabolism- Week 3.pdf - Energy and Metabolism Energy​—this is what the human body requires to maintain homeostasis and to perform its

Energy and Metabolism- Week 3.pdf - Energy and Metabolism...

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Energy and Metabolism Energy —this is what the human body requires to maintain homeostasis and to perform its various functions. The body derives energy from the food we eat and from our food storage reserves. It relies on the precise functioning and interaction of the various components of the digestive system to achieve its goals. Metabolism —changes in the chemicals in the body that occur through various biochemical processes—manifests itself in the transformation of compounds into energy and waste products, and the buildup of tissues and organs from assimilated matter. The two types of metabolism are 1. catabolism , the breakdown of molecules 2. anabolism , the synthesis of larger molecules Throughout our lifetimes, we will digest much food and will build up and shed much of our body mass in pursuing our daily activities. The interplay of these processes illustrates the body's remarkable regulatory response to dietary intake. As part of the body's homeostatic process, it uses energy from food in varying amounts during different physical and mental activities. In order to adapt quickly to circumstances, the body stores energy-rich molecules such as glucose in the liver and muscles in the form of glycogen , and fat in adipose tissues situated throughout the body (mostly near muscles) in the form of triglycerides . ATP, the Source of Metabolic Energy in the Cell Glucose is the main molecule the body uses as fuel to produce the ultimate energy molecule, known as ATP . A denosine t ri p hosphate (ATP) is the energy currency of the cell, and is synthesized in the mitochondrion, the cell's "battery." The vast majority of the metabolic processes rely on the breakdown of ATP into ADP and P i , as shown. ATP = ADP + P i + energy Figure 2.1 shows the structure of ATP and the mechanism of energy production via the breakdown of the third phosphate bond. Figure 2.1 ATP Components
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Source: Frio 2007 Specific enzymes break the third phosphate bond via hydrolysis , releasing energy for enzymes and structural proteins (e.g., muscle) to use in producing movement, synthesizing or breaking down other chemicals in the body, and generating heat, important in regulating body temperature and maintaining homeostasis in cold environments. So, ATP forms when the body uses glucose for fuel, and then it breaks down in the mitochondria, where it is recreated to aid in metabolic processes. Synthesis of ATP: the Chemiosmotic Hypothesis How, then, is ATP synthesized? Dr. Peter Mitchell won a Nobel prize when he elucidated this elaborate mechanism in what he termed the chemiosmotic hypothesis . According to Mitchell, the electron transport system (ETS) creates a proton gradient (a gradual and continuous distribution of protons from low to high concentrations) on one side of a mitochondrion's membrane. This gradient contains a large amount of chemical potential energy, which can be harnessed to synthesize ATP. In ATP synthesis, our earlier equation reverses: ADP + P i + energy = ATP A large enzyme (supramolecular complex) called ATP synthase
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