Thermodynamics: Calculating ΔG and Temperature

Thermodynamics

• The Gibbs free energy equation is ΔG = ΔH – T ΔS, which is used to determine the spontaneity of a reaction.
• In the sample calculation, the ΔG value is 7,350 J.mol-1, indicating a non-spontaneous reaction.
• To find the temperature at which ΔG = 0, the equation 0 = -15,000 J.mol-1 – (X)( -75 J.K-1mol-1) is used, and the solution is X = 200 K or -73℃.

The Origin and Evolution of Life

• The Chemosynthetic Theory was proposed by A.I. Oparin, stating that the Earth initially consisted of hot gases and vapors that eventually cooled and formed a solid crust.
• Heavy rains led to the formation of water bodies, which contained hot water and dissolved methane and ammonia.
• Chemical reactions in the water led to the formation of biomolecules, including amino acids, nitrogenous bases, sugars, and fatty acids.
• These biomolecules eventually combined to form proteins and nucleic acids.

Probable Stages of the Origin of Life

• Stage 1: Sources of energy, such as ultraviolet rays, lightning, or heat, caused reactions that produced complex organic compounds from ammonia, methane, water, and hydrogen.
• Stage 2: Simple organic molecules combined to form large molecules, including peptides, sugars, and fat molecules.
• Stage 3: Large molecules combined to form multimolecular heaps or complexes, which eventually separated from the surrounding solution and formed "coacervate drops".
• Stage 4: Within the coacervate drops, a form of metabolism occurred, with synthesis and breakdown of substances, and RNA molecules may have shown enzymatic activity.

Steroids

• Cholesterol is an animal sterol with a hydroxyl group at C3 and a double bond between C5 and C6, with an 8-carbon aliphatic side chain attached to C17.
• Functions of cholesterol include roles in membrane structure and function, synthesis of bile acids, hormones, and vitamin D.
• Ergosterol occurs in plants, yeast, and fungi, and is a precursor to vitamin D2 when exposed to ultraviolet radiation.

Amphipathic Lipids

• These molecules contain both hydrophobic and hydrophilic groups, making them insoluble in water and forming micelles or bilayers when mixed with water.

Proteins

• Proteins are the most abundant organic molecules in living systems, composed of five major elements in a specific proportion.
• Functions of proteins include structural, dynamic, and enzymatic roles.
• Properties of proteins include precipitation by salts of heavy metals, and color reactions with biuret, ninhydrin, xanthoproteic, and Millon's reagents.
• Denaturation of proteins occurs through physical and chemical agents, leading to a change in physical, chemical, and biological properties.
• Classification of proteins can be based on chemical nature and solubility, function, or nutrition.

Classification of Proteins

• Based on chemical nature and solubility: simple, conjugated, and derived proteins.
• Simple proteins yield only amino acids upon hydrolysis, and include fibrous and scleroproteins like keratin, collagen, and elastin.
• Derived proteins are denatured or degraded products of simple and conjugate proteins, including primary and secondary derived proteins.