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The Importance of the Properties of Water to Life | ||
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
Boil - the conversion of a liquid to a gas by heating up to the boiling point
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
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)
Fatty acid - a long carbon chain with a carboxy terminus
Freeze - 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
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 bonding - 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"
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
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 - 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.
