Metabolism and Energy: Understanding Cellular Processes

Metabolism

• Metabolism is the sum of all chemical reactions that occur in living organisms and is the basis of all life processes.
• Metabolic processes involve degradation, biosynthesis, energy generation, and other cellular activities.
• Metabolic anabolism involves fatty acid biosynthesis, amino acid biosynthesis, nucleotide biosynthesis, neurotransmitter biosynthesis, and gluconeogenesis.
• There are 4 stages of metabolic catabolism: digestion, breakdown of complex biomolecules to small molecules, formation of Acetyl CoA, and citric acid cycle.

Coenzymes

• Coenzymes are non-protein compounds necessary for enzyme-catalyzed reactions to occur.
• Important coenzymes in metabolic pathways are CoA, NAD+, NADP+, and FAD.
• Coenzymes are biologically redox agents that bind and carry high-energy electrons between compounds in cellular pathways.

Nicotinamide Adenine Dinucleotide (NAD+)

• NAD+ is a coenzyme that plays a crucial role in redox reactions.
• Its reactive part is the nicotinamide ring, which participates in metabolic pathways by accepting and donating electrons.
• NAD+ exists in oxidized and reduced states, and its redox equation is: NAD+ + 2e- + 2H+ → NADH + H+

ATP and Energy Generation

• Adenosine triphosphate (ATP) is the energy storage molecule that connects energy-producing reactions with energy-requiring reactions.
• ATP hydrolysis reaction is exothermic, yielding energy for cellular utilization.
• ATP plays a crucial role in catabolic and anabolic reactions, linking energy-producing reactions with energy-requiring reactions.

Gibbs' Free Energy

• Metabolic reactions depend on free energy (G), which is affected by factors such as enthalpy (H), entropy (S), and temperature (T).
• The equation for Gibbs' free energy is: ∆G = ∆H - T∆S.
• Spontaneous reactions occur when ∆G < 0, while spontaneous backward reactions occur when ∆G > 0. Equilibrium is reached when ∆G = 0.