Properties of Water and Biochemical Reactions

Vocabulary flashcards covering chemical and physical properties of water, thermal behavior, transport mechanisms, and metabolic reactions involving condensation and hydrolysis.

Aqueous medium

The liquid environment in which life on Earth arose, with water being the most abundant substance in living systems ($70\%$ or more of the weight of most organisms).

Hydrogen bond (in water)

An electrical attraction between a positively charged region ($\delta^+$ on Hydrogen) and a negatively charged region ($\delta^-$ on Oxygen) of neighboring water molecules, which is continually broken and reformed by thermal motions.

Water polarity

The unequal distribution of electrons in a water molecule ($\text{H}_2\text{O}$) due to Oxygen's high electronegativity, creating partial positive charges ($\delta^+$) on Hydrogen atoms and a partial negative charge ($\delta^-$) on Oxygen.

Universal solvent

Water's ability to dissolve many polar and ionic substances, allowing it to transport essential nutrients as it moves through living organisms.

Cohesion

The attraction between particles of the same substance, which allows water molecules to bond with each other and creates surface tension.

Surface tension

A measure of the strength of water's surface produced by cohesive forces, forming a surface film that enables insects to walk on water.

Adhesion

The attraction between two different substances, enabling water to form hydrogen bonds with other materials such as glass, soil, plant tissues, and cotton.

Capillary action

A phenomenon driven by adhesive and cohesive forces where water molecules tow each other along when confined inside a narrow tube.

Transpiration of Water in Xylem

The process by which water molecules move upward through a xylem vessel with thick walls and stiffed lignin, supported by adhesion between water and xylem walls and cohesion between water molecules.

Specific heat

The amount of heat needed to raise or lower $1\,\text{g}$ of a substance by $1\,^\circ\text{C}$.

Heat of vaporization

The energy required to convert $1\,\text{g}$ of a substance from a liquid to a gas, absorbing significant heat energy as water evaporates.

Ice crystal lattice

A fixed crystal-like array formed when water freezes, keeping water molecules spaced farther apart so that ice is less dense than liquid water and floats to insulate aquatic life.

Condensation reaction

A chemical reaction in which monomers combine via covalent bonds accompanied by the removal or elimination of water elements ($\text{H}_2\text{O}$).

Hydrolysis reaction

A chemical reaction in which a covalent bond between monomers is broken through the addition and consumption of a water molecule ($\text{H}_2\text{O}$).

ATP-ADP cycle

The cellular energy cycle where ATP synthesis from ADP and inorganic phosphate requires energy input ($+\Delta G^0$) via condensation, and ATP cleavage releases energy ($-\Delta G^0$) via phosphate transfer/hydrolysis.

Enzymatic depolymerization

The breakdown of biological polymers such as proteins, carbohydrates, and nucleic acids into smaller units through hydrolysis reactions.

Daily water gain and loss balance

The physiological homeostasis in humans where total daily intake ($2.2\,\text{L/day}$) plus metabolic production ($0.3\,\text{L/day}$) balances total output via skin/lungs ($0.9\,\text{L/day}$), urine ($1.5\,\text{L/day}$), and feces ($0.1\,\text{L/day}$).

Maltose hydrolysis

A hydrolysis reaction in which one maltose molecule reacts with one water molecule ($\text{H}_2\text{O}$) to produce two glucose molecules.

Glucose condensation

A condensation reaction in which two glucose molecules combine to yield one maltose molecule and release one water molecule ($\text{H}_2\text{O}$).

Specific heat of water vs. solids

Water has a high specific heat capacity of $4{,}180\,\text{J/kg}\cdot\text{K}$, compared to sand ($670\,\text{J/kg}\cdot\text{K}$) and asphalt ($900\,\text{J/kg}\cdot\text{K}$).