BIOL lecture 3 second part

High Heat of Vaporization

• Water regulates Earth's climate by absorbing solar heat in oceans, which is released during evaporation.
• Warm tropical air carries water vapor; condensation releases heat, stabilizing temperatures in ecosystems.
• Water has the highest thermal conductivity among liquids, ensuring uniform temperature in lakes and oceans.

Temperature Regulation

• Water remains liquid within a temperature range of 0 - 100° C, facilitating life on Earth.
• Acts as an insulator, retaining body temperature in cold conditions, while also functioning as a coolant through processes like sweating.

Evaporative Cooling

• Increased temperature raises kinetic energy of water molecules, leading to evaporation.
• Evaporation lowers the average kinetic energy of the remaining liquid, resulting in a temperature drop.

Water as a Solvent

• Water, a universal solvent, effectively dissolves polar solutes due to its polarity.
• Hydrophilic (water-loving) substances such as acids, alcohols, and salts dissolve well in water.
• Hydrophobic (water-repelling) substances like lipids do not dissolve in water.

pH of Water

• Pure water has a neutral pH of 7 and does not act as an acid or base; it changes pH when substances dissolve in it.
• Natural rainwater has a slightly acidic pH of 5.6 due to dissolved carbon dioxide and sulfur dioxide.

Acids, Bases, and Buffers

• Organisms are sensitive to pH changes: acids lower pH (<7), while bases increase it (>7).
• pH measures hydrogen ion concentration, defined mathematically as pH = -log [H+].
• Water disassociates into hydroxyl (OH-) and hydrogen (H+) ions, maintaining [H+] = [OH-] in pure water.

Characteristics of Acids and Bases

• Acids donate protons (H+), taste sour, change litmus paper red, and are corrosive.
• Bases accept protons (H+), feel slippery, change litmus paper blue, and can neutralize acids.
• Strong acids and bases fully dissociate in water, while weak acids and bases partially dissociate.

Neutralization Reactions

• Occurs when an acid and base react to form water and a salt: H+(aq) + OH-(aq) → H2O.

Properties of Strong Acids and Bases

• Strong acids (e.g., HCl, H2SO4) and bases (e.g., NaOH, KOH) fully dissociate in solution, resulting in strong proton acceptors or donors.

Dilution of Acids

• When diluting concentrated acids, always add acid to water to avoid hazardous reactions; heat is generated by acid-water interactions.

Buffers

• Buffers resist pH changes with the addition of acids or bases and are crucial for maintaining stable pH in biological systems.
• Common buffers include MES, PIPES, HEPES, and Tris-HCl, with specific pH ranges for effective use.

Buffer Systems in Biology

• Biological systems typically operate within a narrow pH range (7.2 - 7.6) to prevent protein denaturation and cell dysfunction.
• The carbonate/bicarbonate buffering system in blood helps regulate pH, particularly during metabolic processes such as lactic acid production.

Lysosomal Environment

• Animal cells contain lysosomes, pouches with acidic interiors (pH 5) for recycling molecules with enzymes that require low pH for activity.

Explore the significance of water's high heat of vaporization and its role in regulating Earth's climate. This quiz examines how water absorbs and dissipates heat, influences temperature in aquatic ecosystems, and supports movement of warm air. Understand why water is essential for maintaining stable environments.