Energy and Enzymes Overview

Energy and Enzymes

• Primary Energy Source: The sun is the primary energy source for life on Earth.
• Endergonic vs. Exergonic Reactions: An endergonic reaction is an "uphill" run, akin to moving energy from the bottom of an energy hill, storing potential energy in the products. The opposite, exergonic reactions, release energy.
• Transition State and Activation Energy: The high potential energy of the transition state in a reaction is due to the altered three-dimensional structure of reactants during activation.
• Enzyme Characteristics: Enzymes are proteins that function as catalysts, speeding up reactions; they are affected by temperature and pH. Enzymes have active sites.
• Enzymes and Reactions: Enzymes increase the speed of reactions by lowering the activation energy.
• Endergonic and Exothermic: An endothermic reaction absorbs net energy, while an exergonic reaction releases net energy. Reactions that store energy are endergonic.
• Metabolic Pathways: The Krebs cycle exemplifies a cyclic pathway, a series of steps where the initial molecule is regenerated at the end of each cycle.
• ATP Hydrolysis: The phosphate-group transfers in ATP are a rapid, near-universal, and renewable method for energy delivery.
• First Law of Thermodynamics: Energy cannot be created or destroyed; it can only be transferred or transformed.

Thermodynamics

• Second Law of Thermodynamics: Matter tends to become more disorganized (entropy increases) over time. Energy gained by one part of the universe will be lost (converted to heat) by another part.
• Thermodynamic Principles: The first law of thermodynamics states that energy cannot be created or destroyed.

Enzymes and Catalysts

• Catalyst Nature of Enzymes: Enzymes are organic catalysts, increasing reaction rates without being used up in the process. They work best at specific pH values and are proteins, not inorganic molecules.
• Enzyme Active Sites: All enzymes have an active site where substrates temporarily bind.
• Enzyme Behavior: Enzyme shape may change slightly during catalysis, so that the fit is induced. The active site orients substrate molecules to promote interaction of reactive parts. Not all enzymes function in the cytoplasm of the cell.
• Enzyme Inhibition/Activation: Enzymes can be regulated by allosteric activators and inhibitors.
• Coenzymes: NAD+, FAD, and NADP+ are cofactors (organic coenzymes), not metal ions or allosteric regulators.

Electron Transport Systems

• Electron Transport Mechanisms: Electron transport systems involve enzymes, cofactors, and electron transfers across cell membranes.

Energy and ATP

• ATP and Energy: The main significance of the outer phosphate bond in ATP is that it releases a large amount of usable energy when the phosphate group is split off during hydrolysis.
• Allosteric Enzymes: Allosteric enzymes have a separate active site that binds intermediate/end-product molecules, whereas the substrate binds at the active site.

This quiz covers key concepts related to energy and enzymes, including the roles of endergonic and exergonic reactions. Understand the characteristics of enzymes, how they function as catalysts, and their impact on reaction rates. Test your knowledge of activation energy and metabolic pathways.