UNIT 2: Metabolic Processes Intro to Metabolism, Energy, ATP and Redox

Metabolism Living organisms must constantly capture, store and use energy to carry out the functions of life. At any given instant an organism is breaking down macromolecules(catabolic reactions) to release energy, and synthesizing macromolecules (anabolic reactions) which requires energy. The sum of all anabolic and catabolic processes in a cell or organism is called METABOLISM.

Energy Transfer Energy is not easy to obtain; often it is captured in one form and converted to another before it is used. Ex. Plants use photosynthesis to convert light energy to glucose. Ex. Plants and animals use cellular respiration to change macromolecules, like carbohydrates, into a source of useable energy, ATP.

The First Law of Thermodynamics The total amount of the energy in the universe is constant. Energy cannot be created or destroyed, but only converted from one form to another. Energy Chemical Potential energy is energy stored in bonds. Free energy is energy that can do work.

Making and Breaking Bonds Chemical reactions always involve energy changes. Most reactions also include the breaking and making of bonds. Energy is absorbed when a bond is broken and released when a new bond is made.

Bond Energy Bond energy is a measure of the strength of a chemical bond in kJ. The more energy a bond contains, the stronger it is (more stable). Since a high energy bond is hard to break apart it therefore doesn’t release energy freely, and has low potential energy.

Reactions in terms of Free energy Exergonic reactions are reactions that give off free energy. The reactants have high potential energy and low bond energy. They are less stable. It does not take much energy to break the bonds and start the reaction. The products have low potential energy and high bond energy. They are more stable. A lot of energy is released when the product bonds are made. The net result is more energy released than energy used. i.e. Catabolic reactions

Reactions in terms of Free energy Endergonic reactions are reactions that require free energy. The reactants have low potential energy and high bond energy. They are more stable. It takes more energy to break the bonds and start the reaction. The products have high potential energy and low bond energy. They are less stable. Less energy is released when the product bonds are made. The net result is more energy used than energy released. i.e. Anabolic reactions

Endergonic and Exergonic Energy Level Diagrams