Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2-1 Chapter 2 Lecture Outline See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2-2 Matter, Energy, and Life Matter is anything that has mass and occupies space. Energy is the ability to do work. – There are two types of energy: Potential energy – Stored energy, available to do work Kinetic energy – Energy of motion – Potential energy can be converted to kinetic energy to do work.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2-3 Law of Conservation of Energy Energy is never created or destroyed. – The first law of thermodynamics Energy can be converted from one form to another, but the total energy remains constant. – An object at the top of a hill has potential energy based on its location. – When the object rolls down the hill, the potential energy is converted to kinetic energy.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2-4 Forms of Energy There are five forms of energy: 1. Mechanical energy Energy of movement 2. Nuclear energy Energy from reactions involving atomic nuclei 3. Electrical energy Flow of charged particles 4. Radiant energy Energy in heat, light, x-rays and microwaves 5. Chemical energy Energy in chemical bonds

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2-5 What is the nature of matter? Atoms – The smallest units of matter that can exist separately Elements – Chemical substances composed of the same kind of atoms – Listed on the periodic table – Each element is represented by a symbol of one or two letters. – The principal elements that comprise living things are: C, H, O, P, K, I, N, S, Ca, Fe, and Mg.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2-6 The Periodic Table of the Elements

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2-7 Atomic Structure Atoms are composed of: – The atomic nucleus Protons - positively charged – Atomic number  the number of protons – All atoms of the same element have the same number of protons. Neutrons – no charge – Electrons Orbit the nucleus in energy levels Are constantly in motion

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2-8 Atomic Structure

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2-9 Elements Atoms of the same element have equal numbers of electrons and protons. – Thus, they have a neutral charge. Isotopes – Atoms of the same element that have different numbers of neutrons. – Atomic weight  the average of all of the isotopes in a mixture. Mass number – The sum of protons and neutrons in the nucleus.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Isotopes of Hydrogen

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Electrons Electrons occupy specific energy levels around the nucleus. – Electrons closest to the nucleus have the lowest energy. Energy levels hold specific numbers of electrons. – The first energy level can have up to 2 electrons. – All other energy levels can have up to 8 electrons. Atoms seek to have a full outer energy level. – Atoms that have full outer energy levels are inert. – Other atoms seek to fill their outer energy levels through chemical bonds.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Electrons

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display The Formation of Molecules Molecules consist of two or more atoms joined by a chemical bond. A compound is a chemical substance made of two or more elements combined in chemical bonds. – The formula of a compound describes the nature and proportions of the elements that comprise the compound. H 2 O

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Molecules and Kinetic Energy Molecules are constantly in motion. Temperature is a measure of the average speed of the molecules in a substance. – The greater the speed, the higher the temperature. – Measured in Fahrenheit or Celsius Heat is a measure of the total kinetic energy of molecules. – Measured in calories (amount of heat that will raise 1g of water 1 degree Celsius). Heat and Temperature are related. – Add heat energy to a substance and the molecules will speed up, and the temperature will rise.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Kinetic Energy, Physical Changes and Phases of Matter Three phases of matter – Solid – Liquid – Gas The phase in which a substance exists depends on its kinetic energy and the strength of its attractive forces. – Solids  strong attractive forces, low kinetic energy, little to no molecular movement. – Liquid  enough kinetic energy to overcome the attractive forces; more molecular movement. – Gas  high kinetic energy, little to no attractive forces; maximum movement.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Chemical Changes—Forming New Kinds of Matter Chemical reactions – Creating different chemical substances by forming and breaking chemical bonds. – Remember: Atoms form chemical bonds to fill their outermost electron energy levels, achieving stability. There are several types of chemical bonds. – We will discuss: Ionic bonds Covalent bonds

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Ionic Bonds Atoms can gain or lose electrons to achieve a full outermost energy level. – Atoms with charge are called ions. – When an atom gives away an electron, it ends up with more protons than electrons and gains a positive charge; cation. – When an atom accepts an electron, it ends up with more electrons than protons and gains a negative charge; anion. – This process is called ionization. An ionic bond – The attraction between oppositely charged ions Example: NaCl – Sodium (Na) has one electron in its outer energy level. – Chloride has seven electrons in its outer energy level. – Sodium donates an electron to chloride, each achieving stability. – The positively charged sodium is attracted to the negatively charged chloride.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Ion Formation

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Covalent Bonds Atoms can achieve full outermost energy levels by sharing electrons instead of exchanging them. A covalent bond is formed by the sharing of electrons. – The atoms sharing electrons sit close enough together so that their outer energy levels overlap. – Single covalent bond  one pair of electrons is shared. H 2 – Double covalent bond  two pairs of electrons are shared. ethylene – Triple covalent bond  three pairs of electrons are shared. N 2

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Covalent Bonds

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Hydrogen Bonds The positive hydrogen end of one polar molecule is attracted to the negative end of another polar molecule. – This attraction is a hydrogen bond. Hydrogen bonds hold molecules together. – Since they do not hold atoms together, they are not considered true chemical bonds. Hydrogen bonds are very important in biology. – They stabilize the structure of DNA and proteins. – Water molecules can “stick” together with hydrogen bonds.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Water: The Essence of Life Water has special properties that make it an essential molecule for life. –H2O–H2O – Electrons are shared unequally by hydrogen and oxygen. This is a polar covalent bond. Oxygen has more protons than hydrogen. – The electrons spend more time around oxygen than around hydrogen. – The oxygen end of water is more negative. – The hydrogen end of water is more positive.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Hydrogen Bonds

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Mixtures and Solutions A mixture – Matter that contains two or more substances that are not in set proportions A solution is a homogeneous mixture of ions or molecules of two or more substances. – Components are distributed equally throughout. – The process of making a solution is called dissolving. – The solvent is the substance present in the largest amount. Frequently the solvent is a liquid. – The solutes are the substances present in smaller amounts. Aqueous solutions are solids, liquids or gases dissolved in water.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Mixtures vs. Pure Substances

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Water and Life The following properties of water make it essential for life: – High surface tension Water molecules stick to each other via hydrogen bonds. Capillary action moves water through streams, soil, animals and plants. – High heat of vaporization A lot of heat is required to break the hydrogen bonds holding water together. Large bodies of water absorb a lot of heat. – Temperate climates – Evaporative cooling

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Water and Life Unusual density properties – Ice is less dense than water, so ice floats. – Allows aquatic life to survive in cold climates. The universal solvent – Water can form hydrogen bonds with any polar or ionic compound. – Therefore, many things can be dissolved in water.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Chemical Reactions A chemical change: – When the bonds of compounds are made or broken, new materials with new properties are produced. – Happens via chemical reactions. In a chemical reaction the elements remain the same, but the compounds they form and their properties are different.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Chemical Reactions and Energy Chemical reactions produce new compounds with less or more potential energy. – Energy is released when compounds are made with less potential energy. – Energy is used to make compounds with more potential energy.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Chemical Equations A chemical equation is a method of describing what happens in a chemical reaction. – For example, photosynthesis is described by the following equation: Energy + 6CO 2 + 6H 2 O → C 6 H 12 O 6 + 6H 2 O Reactants  substances that are changed, usually on the left side of the equation. Products  new chemical substances formed, usually on the right side of the equation.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Five Important Chemical Reactions in Biology 1. Oxidation–reduction 2. Dehydration synthesis 3. Hydrolysis 4. Phosphorylation 5. Acid–base reactions

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Oxidation-Reduction Reactions Oxidation  reduction reactions – Reactions in which electrons (and their energy) are transferred from one atom to another. – Oxidation An atom loses an electron. – Reduction An atom gains an electron. For oxidation to occur, reduction must also occur. Example: – Respiration Sugar is oxidized to form carbon dioxide and oxygen is reduced to form water. Energy is released in the process. C 6 H 12 O 6 + 6O 2 → 6H 2 O + 6CO 2 + Energy Sugar + oxygen → water+ carbon dioxide + energy

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Dehydration Synthesis Reaction When two small molecules are joined to form a larger molecule, – A molecule of water is released. Example: – Joining amino acids to form proteins. NH 2 CH 2 CO-OH + H-NH CH 2 CO-OH  NH 2 CH 2 CO-NH CH 2 CO-OH + H-OH amino acid 1 + amino acid 2 = protein + water

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Hydrolysis Reactions When a larger molecule is broken down into smaller parts, – A water molecule is split – Opposite of a dehydration synthesis Example: – Digesting proteins into amino acids. NH 2 CH 2 CO-NH CH 2 CO-OH + H-OH  NH 2 CH 2 CO-OH + H-NH CH 2 CO-OH Protein + water = amino acid 1 + amino acid 2

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Phosphorylation Reactions When phosphate groups are added to other molecules, – Phosphate groups are clusters of oxygen and phosphate atoms. Bonds between phosphate groups and other molecules contain high potential energy. – When these bonds are broken, the energy that is released can be used by the cell to do work. – Phosphorylation reactions are commonly used to transfer potential energy. Q-P + Z  Q + Z-P

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Acid-Base Reactions Occurs when ions from an acid interact with ions from a base. This type of reaction allows harmful acids and bases to neutralize one another. H + Cl - + Na + OH - → Na + Cl - + H + OH - Hydrocloric + Sodium Sodium + Water acid hydroxide chloride

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Acids, Bases and Salts An acid – Ionic compounds that release hydrogen ions (H + ) into a solution – Phosphoric acid, hydrochloric acid A base – Compounds that release hydroxide ions (OH-) into a solution – Sodium hydroxide, ammonia Because bases are negatively charged, they will react with a positively charged hydrogen in solution. The strength of an acid or base is determined by how completely it will dissociate in water. – Strong acids release almost all of their hydrogen ions into water. – Strong bases release almost all of their hydroxide ions into water.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Some Common Acids, Bases and Salts

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Salts Neither acids nor bases Usually formed when acids and bases react – The dissociated hydrogen ions and hydroxide ions join to form water. – The remaining ions form ionic bonds, creating a salt. – This is an example of neutralization: H + Cl - + Na + OH - → Na + Cl - + H + OH - Hydrocloric + Sodium Sodium + Water acid hydroxide chloride

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display pH A measure of hydrogen ion concentration Solutions with high hydrogen ion concentrations – Have low pH – Are acidic Solutions with low hydrogen ion concentrations – Have a high pH – Are basic There is a 10-fold difference in hydrogen ion concentration between solutions that differ by one pH unit. – A solution with pH 4 has ten times as many hydrogen ions as a solution with pH 5.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display The pH Scale