Chemistry of Life

Chemistry of Life Chapter 3 Biology Mr. Gilbertson

Atoms • Smallest particle of matter which still retains the property of that material. • Made up of smaller particles • Mostly made up of empty space • So small that they cannot be seen even with the most powerful microscopes • Atoms an element are unique to that element but similar to all other atoms of that element

Elements • Any material that is made up of only one kind of atom • Examples: iron, carbon, gold, oxygen, lead, silver, etc. • There are 90 naturally occurring elements • 13 are man made • Total 103 elements listed • Each is represented by an atomic symbol

CHEMICAL BONDING • All atoms need to have a full outer energy level, filled with electrons to be stable. (for most 8 electrons) • Atoms with less than a full outer energy level will react (lose, gain, or share electrons) with other atoms, to fill the outer energy level and become stable.

COVALENT BONDS • When two or more atoms share electrons to form a molecule • A molecule is a group of atoms held together by covalent bonds • All organic molecules are covalently bonded and made up of molecules (molecular) • Normally the number of electrons and protons is the same in a molecule so they are usually neutral in terms of charge. • Sometimes the electrons are more strongly attracted to one end of a molecule, it is said to be polar

HYDROGEN BONDING • Electrons are shared between atoms, but sometimes they are more attracted to one of the bonded atoms than the other. • This forms a slight difference in charge from one end of a molecule (H2O) to the other. • It is said to have poles, or to be polar • Allows molecules to attract one another, opposite charges attract, like charges repel • Called hydrogen bonding – weak form of chemical bonding

IONIC BONDING • Ions are atoms that are charged due to a loss or gain of electrons • Atoms with less than three electrons in the outer energy level tend to lose electrons (they form positive ions) • Atoms with five or more electrons tend to gain electrons (they form negative ions) • When two oppositely charged ions are attracted to one another (one positive and one negative) an ionic bond is formed. • The bond between sodium (Na) and chlorine (Cl) is an ionic bond.

WATERMOSTIMPORTANTMOLECULETOLIFE • INORGANIC MOLECULE • UNIQUE PROPERTIES POLAR MOLECULE EFFECTIVE SOLVENT STRONG ADHESION STRONG COHESION RESULTS IN CAPILLARY MOVEMENT HIGH SPECIFIC HEAT

+ + + + + H H H H H - - - - - O O O O O + H + + + + H H H H + H + + + H H H + H - - - - O - O O O O H + H H H + + + H + + + + + + H H H H H - - - - - O O O O O + H + + + + H H H H COHESION OF WATER WATER FORMS AN ORGANIZED PATTERN OF MOLECULES ALL OF WHICH ARE ATTRACTED TO EACH OTHER

COHESION OF WATER • Caused by hydrogen bonding • Cohesion refers to the attraction between molecules of the same substance • Enables water to form a thin film or a drop • Molecules at the surface are linked tightly so they form a “skin” known as surface tension • Surface tension prevents water surface from stretching or breaking easily. • Requires more energy to evaporate.

ADHESION OF WATER • The attraction of molecules of different substances • Water is attracted to solid surfaces. • Causes some surfaces to get “wet” • Adhesion powers the process of capillary action in which water moves upward in narrow tubes such as plant stems • The attraction due to adhesion is stronger than the force of gravity so the water “climbs” the tube. (Max height is 32ft or 9.8m)

High Specific Heat of Water • Water absorbs heat more slowly than other substances • Organisms are able to get rid of excess heat by evaporation of water (sweat) • Enables organisms to maintain a constant temperature even in a changing environment. • Helps maintain homeostasis

AQUEOUS SOLUTIONS • Water is called the universal solvent • Almost anything will dissolve in water to some extent • A solution is a mixture in which one or more substances are uniformly distributed in another (kool-aid) • Many important substances in the body are dissolved in blood or other body fluids • Any solution in which one of the components is water is said to be an aqueous solution. • Aids in transportation of materials within cells and within organisms

+ H - O + H POLARITY OF WATER THE POLARITY OF WATER IS CAUSED BY THE UNEQUAL DISTRIBUTION OF ELECTRONS, SINCE THE ELECTRONS STAY WITH THE OXYGEN IT TENDS TO HAVE A SLIGHTLY NEGATIVE CHARGE

POLARITY OF WATER • Enables water to dissolve a great number of organic compounds (polar molecules) • Enables water to dissolve ionic compounds (mineral ions) • Nonpolar molecules do not dissolve well in water they tend to clump. • The nonpolar cell membrane tends to form a boundary past which polar water molecules cannot easily pass.

ACIDS AND BASES • In water there are some molecules which will dissociate into ions H+ (Hydronium ion) and OH-(Hydroxide ion) • Any solution which produces a higher than normal concentration of H+ ions is called an Acid • Any solution which produces a higher concentration of (OH-) ions is a base or alkaline solution. • pH is a measure of the inverse H+ ion concentration • A pH of 7 is neutral, a pH of less than 7 is acid, and a pH greater than 7 is a Base • If you add an acid and a base they will neutralize

Chemistry of Life