AP Bio Chapter 8 - Metabolism Flashcards

Metabolism Overview

• Metabolism encompasses all chemical reactions in an organism, showcasing life through molecular interactions in cellular environments.
• Metabolic pathways are sequences of reactions starting with a specific molecule, which is transformed through defined steps by specific enzymes, culminating in a particular product.

Catabolic and Anabolic Pathways

• Catabolic pathways break down complex molecules into simpler compounds, releasing energy; cellular respiration exemplifies this by converting glucose into carbon dioxide and water.
• Anabolic pathways utilize energy to construct complex molecules from simpler ones, such as synthesizing proteins from amino acids, leveraging energy sourced from catabolic processes.

Energy Concepts

• Bioenergetics studies energy flow in organisms, with energy defined as the capacity to initiate change.
• Kinetic energy relates to an object's motion; potential energy refers to energy due to an object's position or structure.
• Chemical energy, a type of potential energy, is available for release in chemical reactions, notably high in glucose.

Thermodynamics Principles

• Thermodynamics examines energy transformation; the first law asserts energy conservation—energy cannot be created or destroyed, only converted.
• The second law states that energy transformations increase entropy, indicating a natural trend towards disorder.

Free Energy and Stability

• Free energy indicates a system's capacity to do work; it is high in unstable systems (+G) and low in stable systems (-G).
• Exergonic reactions release free energy, signified by negative Gibbs free energy, while endergonic reactions absorb energy and are characterized by positive Gibbs free energy.

Cellular Work Types

• Chemical work facilitates non-spontaneous reactions, such as polymer synthesis.
• Transport work involves moving substances across membranes against spontaneous movement.
• Mechanical work relates to movements like muscle contraction and cilia beating.

ATP and Energy Coupling

• ATP, composed of ribose, adenine, and three phosphate groups, serves as the primary energy currency in cells.
• Energy coupling refers to the process where an exergonic reaction drives an endergonic one, with ATP commonly mediating this process.

Enzyme Function and Regulation

• Enzymes act as catalysts, expediting reactions without being consumed; they reduce activation energy required for reactions.
• The activation energy is the energy necessary to initiate biochemical reactions, and the enzyme-substrate complex is formed when an enzyme binds to its substrate at the active site.
• Enzymes can be influenced by inhibitors, which can be competitive (competing with substrates) or noncompetitive (binding elsewhere to alter enzyme shape).

Enzyme Models and Reactions

• The lock-and-key model describes enzyme specificity, while the induced fit model illustrates how enzymes and substrates shape each other for optimal interaction.
• Feedback inhibition regulates metabolic pathways, where end products inhibit early enzymes to conserve resources.

Environmental Effects on Enzymes

• Optimal conditions for enzyme activity include a temperature range of 35-40°C and a pH range of 6-8, crucial for maintaining enzymatic function in the human body.

Summary of Key Reactions and Energies

• Hydrolysis of ATP (ATP → ADP + P(i)) releases -7.3 kcal/mol of energy, while synthesis (ADP + P(i) → ATP + H2O) requires +7.3 kcal/mol.
• Aerobic cellular respiration (C6H12O6 + 6O2 → 6CO2 + 6H2O) releases -686 kcal/mol of Gibbs free energy.

Additional Terms

• Entropy reflects disorder in a system; enthalpy indicates order.
• Saturation in enzymes occurs when products are promptly replaced by new substrates.
• Cofactors assist enzymes in reactions; coenzymes, typically vitamins, are inorganic cofactors.