Chemistry of Water and Carbon

Structure of Water

• Water is composed of two hydrogen atoms and one oxygen atom linked by a single covalent bond, forming a molecule with a bond angle of 104.5°.
• The molecule acts as an electric dipole, with δ+ and δ- charges on the hydrogen and oxygen atoms, respectively.
• Water molecules form hydrogen bonds (H-bonds) with themselves and other molecules, which are weaker and longer than covalent bonds but are one of the strongest intermolecular forces.

Properties of Water

• Water is a liquid at ambient temperature, binding 3.4 other water molecules.
• At freezing temperature, water is ice, binding 4 other water molecules, and forms an insulating blanket.
• Water has a high melting point, high boiling point, high specific heat capacity, and high heat of vaporization.
• Water's high specific heat capacity allows it to absorb and release heat energy without a large change in temperature.

Biological Applications of Water's Properties

• Water's liquid state over a wide temperature range allows for chemical reactions, circulation, and exploitation by microorganisms.
• Water's excellent solvent properties enable chemical reactions, waste removal, and delivery of food materials.
• Water's ionizing solvent properties are important for nerves and other excitable tissues.
• Water's low viscosity is important for circulatory systems.
• Water's high surface tension tends to make lung alveoli collapse.
• Water's high heat of vaporization is used by mammals for sweating.

Carbon and Its Importance in Biological Molecules

• Carbon is the central atom of life, containing 4 electrons in its outer shell.
• Carbon forms part of essential macromolecules, including pyrimidine, purine, glucose, amino acids, and fat.
• The molecular shape of carbon-containing molecules is important for their function, as structure dictates function.

Physiological Buffers

• Important physiological buffers include the hypothalamus, renal function, and ionization of pure water into positively and negatively charged ions.
• Pure water is pH neutral, with an ionization reaction of H2O ⇌ H+ + OH-.

Ionization of Pure Water

• The ionization of pure water results in the formation of positively and negatively charged ions, with a concentration of hydrogen ions determined by the equation n = mm/MM = 1000 g = 55.5 moles.