The Importance of the Properties of Water to Life

Adhesion - the sticking together of molecules of different substances, such as water adhering to paper

Amino acid - basic structural unit of proteins possessing carboxy and amino terminals (ends).

Amphipathic - a molecule that is "water-loving" (i.e., polar) at one end and "water-hating" (i.e., nonpolar) at the other end; helps hold polar and nonpolar molecules together; characteristic of detergents and of the phospholipid molecules in the membranes of living things

Boiling - the conversion of a liquid to a gas by heating up to the boiling point

Boiling point - the temperature at which a liquid turns into a gas; for water, the temperature is relatively high, 100 o C. or 212 o F at sea level

Capillary action - the tendency of a liquid substance to move along the surface of solid substance due to adhesion (as in water climbing a glass tube or inside a tree), even in spite of gravitational or other forces acting in the opposite direction

Cohesion - the tendency of like molecules to be attracted to one another, as occurs with polar water molecules; such molecules form a highly dynamic structure involving many rapidly breaking and forming hydrogen bonds; water has high cohesion, enough so that insects can walk on water

Condensation - the change of state from gas to liquid due to cooling, as when water vapor turns into water droplets

Density - the mass per unit volume of a substance.

Detergent - organic compound or combination of compounds composed of molecules containing both hydrophilic and hydrophobic portions (that is, polar and non-polar parts)

Evaporation - the change of state from liquid to gas, as when a water molecule evaporates to form (invisible) water vapor; promoted by the addition of heat which results in breaking of hydrogen bonds between water molecules

Fatty acid - a long carbon chain with a carboxy terminus

Freezing - the change of state from liquid to solid, as when water turns to ice, promoted by lowering the temperature; cooling slows down the movement of the molecules, producing a solid substance

Freezing point - the temperature at which a substance turns from a liquid into a solid; water is different from nearly all other substances because it is densest in liquid form at about 4 o C., less dense in solid form at 0 o

Gas - the state of matter in which a substance has no definite shape and a volume defined largely by the size of its container (as well as the temperature and pressure); molecules are widely separated and in constant random motion. Examples include water vapor and air (a mixture of gases).

Hydrogen bonds - weak bonds that form between small molecules (or within macromolecules), specifically involving an atom that has a partial negative charge, especially oxygen in water and in living things, and another atom (such as hydrogen) having a partial positive charge; results in 'sticking together' of molecules

Hydrophilic - polar compounds that dissolve in water, like salt, and are considered "water-loving"

Hydrophobic - nonpolar compounds that do not dissolve in water, such as oil, and are considered "water-hating"

Ice - frozen water or water in its solid state; molecules move apart (compared to their close association in cold water) to form a latticework of hydrogen-bonded molecules; molecules vibrate in their fixed positions

Insulin - the pancreatic hormone that regulates glucose uptake in the cells of the liver and other organs.

Liquid - a fluid in a state intermediate between a solid and a gas, it tends to take the shape of its container, remain at the bottom of the container; the volume of a liquid changes little with changes in pressure; molecules move freely past one another

Melting - the change of state from solid to liquid, as when ice turns to water, promoted by raising the temperature; heating increases the movement of the molecules, producing a liquid substance

Melting point - the temperature at which a solid turns into a liquid, as when ice turns to water

Micelle - small particle formed by aggregates of detergent like molecules; the polar ends of these molecules will arrange themselves externally and the non-polar ends will arrange themselves internally. In washing clothes, the soap forms micelles around the dirt/grease. The water then washes the micelles away from the clothes.

Nonpolar - molecules without an electrical charge, like lipids, that do not dissolve in water

Phospholipid bilayer - the main component of cellular membranes - phospholipids have a non-polar fatty acid chain at one end and a polar phosphate group at the other; this facilitates the formation of a double layer of phospholipids such that the non polar groups interact with each other and the polar groups interact with the cellular cytoplasm and interstitial fluid.

Polar - a characteristic of a molecule that has a greater electron density at one end than the other

Polarity - possessing two opposed poles; a characteristic of molecules which have unequal distributions of charge; water is polar because the oxygen has a partial negative charge and the hydrogen atoms each have a partial positive charge; polar molecules interact with other polar and charged molecules and ions

Polar molecule - a molecule that has a greater electron density at one end the other

Surface tension - not in a liquid or a gaseous state; the state of matter in which molecules vibrate but remain in fixed positions relative to one another, as in ice or wood; substance retains its shape

States of Matter - typically refers to the three primary states of matter: solid, liquid and gas

States of Water - the three primary states of water are ice, liquid water, and water vapor

Sublimation - the change of state from solid to gas, as when ice turns to water vapor or dry ice to carbon dioxide, promoted by raising the temperature; heating increases the movement of the molecules and can produce a gaseous substance

Surface tension - the tendency of molecules of a liquid to stick together at the surface, as occurs with water due to its polarity and hydrogen bonding; a special case of cohesion

Testosterone - the most abundant male steroid hormone which stimulates the development and maintenance of the male reproductive system and secondary sex characteristics.

Transport protein - a protein that carries a molecule through some part of the body such as the blood stream or across a membrane; for example, hemoglobin is a transport protein inside of red blood cells that carries oxygen from the lungs to the rest of the body.

Vitamin A - a fat-soluble vitamin found in green vegetables and retinol in milk, butter, cheese and margarine. Maintains epithelial tissues.

Vitamin E - a fat-soluble vitamin found in seeds, green leafy vegetables and margarine. Functions as an antioxidant prevent cell membrane damage.

Water - transparent, tasteless liquid composed of molecules each containing two hydrogen atoms and one oxygen atom

Water vapor - invisible gas composed of H20 molecules; gaseous state of water


















u& &