BIOENERGETICS

BIOENERGETICSCHAPTER 33ENERGY CHANGES IN LIVING ORGANISMSBioenergetics

is a field in biochemistry that concerns energy flow through living systems. This is an active area of biological research that includes the study of thousands of different cellular processes such as cellular respiration and the many other metabolic processes that can lead to production and utilization of energy in forms such as ATP(Adenosine triphosphate) molecules.METABOLISM AND CELL STRUCTUREMETABOLISM is the sum of all chemical reactions that occur within a living organism.

ANABOLISMis the process by which simple substances are synthesized (build up) into complex substances. CATABOLISMis the process by which complex substances are broken down into simple substances.

PROCARYOTEScell without internal membrane-bound bodies.EUCARYOTESis any organism whose cells contain a nucleus and other organelles enclosedwithin membranes.

ORGANELLE is a specialized subunit within a cell that has a specific function. Individual organelles are usually separately enclosed within their own lipid bilayer.

BIOLOGICAL OXIDATION-REDUCTION: ENERGY DELIVERYThe large quantity of NADH resulting from glycolysis, fatty acid oxidation, and the TCA cycle used to supply the energy for ATP synthesis via oxidative phosphorylation. Oxidation of NADH with phosphorylation of ADP to form ATP are processes supported by the mitochondrial electron transport assembly and ATP synthase, which are integral protein complexes of the inner mitochondrial membrane. The electron transport assembly is comprised of a series of protein complexes that catalyze sequential oxidation reduction reactions; some of these reactions are thermodynamically competent to support ATP production via ATP synthase provided a coupling mechanism, such as a common intermediate, is available. Proton translocation and the development of a trans membrane proton gradient provides the required coupling mechanism.

MOLECULAR OXYGEN AND METABOLISMAlthough a discussion of metabolism justify focuses on carbon, molecular oxygen also plays a critical role in energy production. This diatomic molecule acts as the final receptacle for electrons in the mitochondrial electron-transport system. Aerobic metabolism (i.e., metabolism in the presence of molecular oxygen) is the best way to produce energy for most cells. However, like a very potent drug, oxygen can also be dangerous to life.Mitochondria have become experts at handling this dangerous chemical. The chemical reactions inside these organelles are specifically designed to carry out a four-electron redox with diatomic oxygen:O2 + 4e- + 4H+ H2O2HIGH-ENERGY PHOSPHATE BONDSA phosphate linkage present in certain intermediates of carbohydrate metabolism and containing the energy used in metabolic processes or transferred or stored. Also called high-energy phosphate.BONDthe linkage between atoms or radicals of a chemical compound, or the symbol representing this linkage and indicating the number and attachment of the valencies of an atom in constitutional formulas, represented by a pair of dots or a line between atoms, e.g., HOH, HCCH or H:O:H, H:C:::C:H.

HIGH-ENERGY PHOSPHATE Those phosphate esters and phosphoanhydrides that, on hydrolysis, yield an unusually large amount of energy; e.g., nucleotide polyphosphates such as ATP, and enol phosphates such as phosphoenolpyruvate.

PHOSPHORYLATION: ENERGY CONVERSIONThus far, we have considered two forms for chemical storage of biological energy: reduced carbon atoms and high-energy phosphate bonds. It is vital that the cell be able to convert one form of stored energy to the other.Phosphorylation is the addition of a phosphate (PO43) group to a protein or other organic molecule (see also: organophosphate). Phosphorylation turns many protein enzymes on and off, thereby altering their function and activity. Protein phosphorylation is one type of post-translational modification.

Substrate-level phosphorylation is a type of metabolic reaction that results in the formation of adenosine triphosphate (ATP) or guanosine triphosphate (GTP) by the direct transfer and donation of a phosphoryl (PO3) group to adenosine diphosphate (ADP) or guanosine diphosphate (GDP) from a phosphorylated reactive intermediate. Note that the phosphate group does not have to come directly from the substrate. By convention, the phosphoryl group that is transferred is referred to as a phosphate group.

Oxidative phosphorylation (or OXPHOS in short) is the metabolic pathway in which the mitochondria in cells use their structure, enzymes, and energy released by the oxidation of nutrients to reform ATP. Although the many forms of life on earth use a range of different nutrients, ATP is the molecule that supplies energy to metabolism. Almost all aerobic organisms carry out oxidative phosphorylation. This pathway is probably so pervasive because it is a highly efficient way of releasing energy, compared to alternative fermentation processes such as anaerobic glycolysis.

PHOTOSYNTHESISPhotosynthesis is a process used by plants and other organisms to convert light energy, normally from the Sun, into chemical energy that can be later released to fuel the organisms' activities. This chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water.

THANK YOU FOR LISTENING!!!!