Enzymes and Energetics Quiz

Enzymes and Energetics

• Enzymes are biological catalysts that accelerate chemical reactions by lowering the activation energy (Ea).
• Enzymes achieve this by aligning substrate functional groups, stretching substrate bonds, and creating microenvironments.
• The rate of enzymatic reactions depends on the substrate concentration and the availability of enzyme active sites.
• Enzymes require cofactors (e.g., ions) and coenzymes (e.g., NAD+) for optimal activity.
• Enzyme activity is influenced by environmental factors such as temperature, pH, and salinity.
• Enzymes can be inhibited by competitive inhibitors (block active site) and non-competitive inhibitors (deform active site).
• Inhibition can be irreversible or reversible.

Enzyme Affinities and Cycles

• Enzymes exhibit specificity for substrates due to the complementary shape between the substrate and the enzyme's active site.
• Enzyme-substrate complexes undergo conformational changes during catalysis, resulting in product formation.
• A single enzyme molecule can catalyze multiple cycles of the same reaction without being destroyed.

Activators and Inhibitors

• Allosteric activators stabilize the active form of allosteric enzymes, while allosteric inhibitors stabilize the inactive form.
• Feedback inhibitors regulate biochemical pathways by inhibiting enzymes involved in earlier steps, often through reversible non-competitive inhibition.

Biochemical Pathways

• Biochemical pathways consist of a series of linked chemical reactions where the product of one reaction serves as the reactant for the next.
• The rate-limiting reaction in a pathway is the slowest step, often targeted by pharmaceuticals to modify pathway activity.

Basics about Energy

• Energy is the capacity to perform work. It can be stored (potential energy) or actively doing work (kinetic energy).
• Energy exists in different forms: solar, electrical, mechanical, chemical, and heat.
• Chemical energy is stored within chemical bonds and can be transferred when bonds break.
• Solar energy has a higher potential to perform work than heat.

Thermodynamic Laws

• Thermodynamics studies energy transfer and transformation.
• The First Law states that energy cannot be created or destroyed, only transferred and transformed.
• Photosynthesis transforms solar energy into chemical energy, while cellular respiration converts chemical energy into ATP.
• ATP powers various biological processes.
• Energy transformations are not 100% efficient, resulting in heat production.
• The Second Law states that energy transfer during transformation increases the entropy (disorder) of the universe.
• Biological systems require energy to maintain order and fight against entropy.

Who Says Energy is Free? (Gibbs Energy)

• Free energy (G) is the energy available to perform work.
• Change in free energy (ΔG) indicates energy released (exergonic, negative ΔG) or required (endergonic, positive ΔG).
• Exergonic reactions are spontaneous as reactants have more free energy than products.
• Endergonic reactions are non-spontaneous as products have more free energy than reactants.

Cells Transform Energy

• Photosynthesis is an endergonic process requiring solar energy to synthesize glucose.
• Cellular respiration is an exergonic process that releases energy from glucose into ATP and heat.

Don’t Equilibrate to Live

• Many chemical reactions are reversible and reach equilibrium where ΔG is zero, resulting in no free energy for work.
• Biota must maintain a negative ΔG to perform work and survive.
• The metabolic steady state describes the ongoing process of maintaining a negative ΔG.