Biochemistry: Chemical Foundation - Water and Buffers

Flashcards covering the properties of water, cohesion, adhesion, surface tension, hydrophilic/hydrophobic classification, pH, acids, bases, and buffer systems.

Water Molecule Structure

The structural representation of a water molecule, featuring a covalent bond length of $0.095\,\text{nm}$ and a bond angle of $104.3^\circ$.

Cohesion

The attraction between water molecules driven by hydrogen bonding, which keeps the molecules together at the liquid-air interface.

Surface Tension

The capacity of a substance to withstand rupture when placed under tension or stress, arising directly from cohesion.

Adhesion

The attraction between water molecules and other types of molecules.

Hydrophobic Compounds

Nonpolar compounds, such as hydrocarbons (hexane) and lipids (fats and cholesterol), that do not interact favorably with water.

Hydrophilic Compounds

Compounds that readily interact with water, including ionic compounds ($\text{NaCl}$), polar organic compounds (alcohols, ketones, or carbonyls), weak acids (phosphates, amino acids), and sugars/carbohydrates.

Free Energy Change ($\Delta G$)

A measure of solubility calculated using the equation $\Delta G = \Delta H - T\Delta S$, where $H$ is enthalpy (heat at constant pressure), $S$ is entropy, and $T$ is temperature in Kelvin.

Lipid Assemblies in Aqueous Solution

Structures formed by amphipathic lipid molecules in water, including lipid bilayers (sheets), liposomes, and micelles.

pH

A measure of a solution's acidity or alkalinity on a scale from $0$ to $14$, where a one-unit change corresponds to a tenfold change in hydrogen ion concentration.

Acids

Substances that provide hydrogen ions ($\text{H}^+$) and lower pH; stronger acids donate $\text{H}^+$ more readily.

Bases

Substances that provide hydroxide ions ($\text{OH}^-$) and raise pH by combining with $\text{H}^+$ to produce water.

Physiological pH Range

The narrow window of pH $7.2$ to $7.6$ within which most human body cells operate to prevent organ malfunction, coma, or death.

Buffers

Chemical systems that prevent radical changes in fluid pH by absorbing excess $\text{H}^+$ and $\text{OH}^-$ ions.

Carbonic Acid-Bicarbonate Buffer System

A vital physiological buffer system consisting of carbonic acid ($\text{H}_2\text{CO}_3$) and bicarbonate ($\text{HCO}_3^-$) that stabilizes human body pH.