Essentials of Anatomy and Physiology Fifth edition Seeley, Stephens and Tate Slide 2.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 2: The Chemical Basis of Life

Matter and Energy Slide 2.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Matter – anything that occupies space and has mass (weight) Energy – the ability to do work Chemical Electrical Mechanical Radiant

Composition of Matter Slide 2.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Elements: all atoms of a specific size and weight Fundamental units of matter 96% of the body is made from four elements Carbon (C) Oxygen (O) Hydrogen (H) Nitrogen (N)

Atoms Slide 2.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Basic subunits of elements Consist of subatomic particles Protons: “+” charge, mass of 1 amu Neutrons: “0” charge, mass of 1 amu Electrons: “-” charge, “no” mass Periodic Table lists “neutral atoms”: uncharged particles

Atomic Structure Slide 2.3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Nucleus Protons (p + ) Neutrons (n 0 ) Outside of nucleus Electrons (e - ) Figure 2.1

Identifying Elements Slide 2.4 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Atomic number Equal to the number of protons that the atoms contain Atomic mass number (weight) Sum of the protons and neutrons

Molecules and Compounds Slide 2.7 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Molecule – two or more like atoms combined chemically Compound – two or more different atoms combined chemically In Life Sciences, “molecule” is more common terminology

Chemical Reactions Slide 2.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Atoms are united by chemical bonds. This stores energy Atoms dissociate from other atoms when chemical bonds are broken. This releases energy.

Electrons and Bonding Slide 2.9 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Electrons occupy energy levels called electron shells or orbitals Electrons closest to the nucleus are most strongly attracted (“+” to “-”) Each shell has distinct properties

Electrons and Bonding Slide 2.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Properties of Shells/Orbitals: Number of electrons has an upper limit Shells closest to nucleus fill first Bonding involves interactions between electrons in the outer shell “Full” outer shells do not form bonds

Reactive Elements Slide 2.12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Outer shells are not full and are unstable Tend to gain, lose, or share electrons Allows for bond formation, which produces stability Figure 2.4b

Chemical Bonds Slide 2.13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Ionic Bonds Form when electrons are completely transferred from one atom to another Ions Charged particles produced by the movement of e - between atoms Atom is no longer “neutral”: WHY??

Ionic Bond Formation Sodium (Na + ) and Chloride (Cl-) ions form when an e - is transferred

Chemical Bonds Slide 2.13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Molecules formed by ionic bonding dissociate in water (water is polar) Electrolyte solutions Water with dissociated “free” ions Conduct electricity Found in all body fluids

Chemical Bonds Slide 2.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Covalent Bonds Formed by sharing of electrons between two atoms Single covalent bonds share one electron Double covalent bonds share two electrons Figure 2.6c

Examples of Covalent Bonds Slide 2.15 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 2.6a, b

Polarity Slide 2.16 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Covalently bonded molecules Some are non-polar Electrically neutral Some are polar Have a positive and negative side Figure 2.7

Chemical Bonds Slide 2.17 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Hydrogen bonds Weak chemical bonds Hydrogen is attracted to negative portion of polar molecule Provides attraction between molecules Found in water, proteins, nucleic acids

Hydrogen Bond Formation Hydrogen bonds form between atoms such as oxygen (red) and hydrogen (blue) in water (H 2 O) molecules

Patterns of Chemical Reactions Slide 2.18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Synthesis reaction (A+B  AB) Atoms or molecules combine Energy is absorbed for bond formation Decomposition reaction (AB  A+B) Molecule is broken down Chemical energy is released

Synthesis and Decomposition Reactions Slide 2.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 2.9a, b

Patterns of Chemical Reactions Slide 2.20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Exchange reaction (AB + C  AC + B) Involves both synthesis and decomposition reactions Switch is made between parts of molecules, and different molecules are made Enzymes are usually involved… (later)

pH and Buffers Slide 2.20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Buffers: chemicals that maintain a constant pH in a solution pH: a measure of acidity; the “negative log” of the [H + ] Based on the concentration of (H + ) in solution H + come from water that has dissociated (ionized)

pH and Buffers Slide 2.20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings pH measurements use scientific notation At room temp., 1/10,000,000 water molecules ionizes Count the “zeros”: there are 7, so… H 2 O  H + + OH -, and the pH at room temp is “7”, a neutral pH (equal numbers of “water ions”)

pH and Buffers Slide 2.20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Acid: chemicals that release H + into a solution when they dissociate Base: chemicals that absorb H + or that release OH - when they dissociate

pH and Buffers Slide 2.20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings pH scale is from 0 – 14 “7” is “neutral” 0 – is acidic – 14 is basic (alkaline)

pH Slide 2.25 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Measures relative concentration of hydrogen ions pH 7 = neutral pH below 7 = acidic pH above 7 = basic Buffers Chemicals that maintain a constant pH Figure 2.11

Inorganic Compounds Slide 2.24 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Inorganic compounds Lack carbon (a few exceptions) Tend to be simpler molecules Examples: H 2 O (water) CO 2 (carbon dioxide)

Other Inorganic Compounds Slide 2.24 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Acids Proton [H + ] donors Bases Proton acceptors Neutralization reaction Acids and bases react to form water and a salt

Important Inorganic Compounds Slide 2.22 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Water Most abundant inorganic compounds Vital properties High heat capacity Polarity/solvent properties Chemical reactivity Cushioning

Important Inorganic Compounds Slide 2.23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Salts Easily dissociate into ions in the presence of water Vital to many body functions Include electrolytes which conduct electrical currents