Bio 1010 Dr. Bonnie A. Bain Office: Science 108 E-mail: bain@dixie.edu

CHAPTER 2: CHEMISTRY Why talk about Chemistry in a Biology Class?? Many concepts in this class involve a basic understanding of Chemistry Elements: 92 naturally occurring elements 25 of which are essential to all life

Figure 1.3_3 Life has different levels of complexity

Primary (96% of body weight) H, C, N2, O2 Elements found in the Human Body Primary (96% of body weight) H, C, N2, O2 Secondary (3.9% of body weight) Ca, P, K, S, Na, Cl, Mg Trace elements (less than 0.01% of body weight) Fe, Cr, I, Si, etc.

Trace elements: less than 0.01% Fig. 2-02 Carbon (C): 18.5% Oxygen (O): 65.0% Calcium (Ca): 1.5% Phosphorus (P): 1.0% Potassium (K): 0.4% Sulfur (S): 0.3% Sodium (Na): 0.2% Chlorine (Cl): 0.2% Magnesium (Mg): 0.1% Hydrogen (H): 9.5% Trace elements: less than 0.01% Boron (B) Manganese (Mn) Chromium (Cr) Molybdenum (Mo) Nitrogen (N): 3.3% Cobalt (Co) Selenium (Se) Copper (Cu) Silicon (Si) Fluorine (F) Tin (Sn) Iodine (I) Vanadium (V) Iron (Fe) Zinc (Zn)

Figure 2.3

Fig. 2-03 GOITER

CHAPTER 2: CHEMISTRY Matter: Occupies space, has mass, has weight 4 states: solid, liquid, gas, plasma composed of elements Energy: “The capacity to do work” Potential Energy: Stored energy (eg. battery) Kinetic Energy: Energy of motion (falling objects, explosions, etc.)

Different Forms of Energy Chemical Energy: Energy stored in chemical bonds Most important kind for biology Radiant Energy: Heat and light Electrical Energy: the flow of electrons

PERIODIC TABLE OF THE ELEMENTS Figure 2.2 PERIODIC TABLE OF THE ELEMENTS

Bohr Atom (named after Neils Bohr) Figure 2.5 Bohr Atom (named after Neils Bohr)

ATOMIC NUMBER: Number of protons Hydrogen has 1 proton, Atomic number = 1 Helium has 2 protons, Atomic number = 2 Oxygen has 8 protons, Atomic number = 8 ATOMIC WEIGHT: Protons + neutrons Measured in atomic mass units Carbon has 6 protons + 6 neutrons Atomic weight = 12 (Electrons don't weigh much, not usually counted)

PERIODIC TABLE OF THE ELEMENTS Figure 2.2 PERIODIC TABLE OF THE ELEMENTS

126C Top number = Atomic Weight Bottom number = Atomic Number

Electrons are arranged in shells or orbits around the nucleus

Electron Shells or Orbitals Innermost shell can hold a max. of 2 electrons Next shell holds a max. of 8 electrons, etc. Carbon has 6 protons and 6 electrons Innermost shell has 2 electrons Outer shell has 4 electrons The outer shell can potentially hold 4 more electrons This allows Carbon to combine with other elements

When the outermost shell is full, the element is stable To achieve stability, atoms can either empty their outermost electron shell or fill it to the max. To do this, they can: Give up an electron or Accept an electron Share an electron

Valence Number The number of extra electrons in the outer shell or The number of deficient electrons in the outer shell This determines the combining capacity If an element has 1 electron in the outer shell, it can combine with another element that has 7 in its outer shell.

If an element has 1 electron in the outer shell, it can combine with another element that has 7 in its outer shell. Sodium (Na) valence # = +1 Electron donor Chlorine (Cl) valence # = -1 Electron acceptor

Two atoms “share” electrons Example: Hydrogen is always found as H2 CHEMICAL BONDS IONIC BOND electron donor + electron acceptor Na+1 + Cl-1 = NaCl Held together by the attraction of the + and - charges COVALENT BOND Two atoms “share” electrons Example: Hydrogen is always found as H2 (see polar vs non-polar)

CHEMICAL BONDS (cont.) HYDROGEN BOND Occurs when a covalently bonded hydrogen is positive and is attracted to a negatively charged atom nearby These bonds are relatively weak, can be broken easily, usually indicated by dotted lines Hydrogen bonds form in water, also in large protein molecules

H2O (Water)

POLAR VS NON-POLAR MOLECULES In a covalent bond, the atoms share the electron NON-POLAR COVALENT BOND Neither atom attracts the shared electron more strongly Bonds between 2 identical atoms are always non-polar The single covalent bond between C and H is always non-polar

POLAR COVALENT BOND The sharing of the electron is unequal This affects the chemical properties of the molecule The “stronger” atom has a partial negative charge The “weaker” atom has a partial positive charge Example: water (H2O) This structure gives water its unique properties (universal solvent-can dissolve nearly anything)

Figure 2.11 WATER

Extra Photo 02.11x1

1. Excellent solvent for polar (charged) molecules and ionic salts PROPERTIES OF WATER 1. Excellent solvent for polar (charged) molecules and ionic salts (ie. Many things dissolve readily in water) Example: NaCl (salt) Negative ends of water molecules are attracted to the Na+ Positive ends of water molecules are attracted to the Cl- This pulls the NaCl molecule apart

PROPERTIES OF WATER (cont.) Hydrophilic (water loving) Ions and molecules which interact with water Hydrophobic (water hating) Non-ionized and non-polar molecules These do not interact with water

PROPERTIES OF WATER (cont.) 2. Water molecules are cohesive (stick together) This allows water to do things like fill a glass Also gives water a high surface tension The water molecules cling together because of the hydrogen bonds

Figure 2.13 Surface tension

PROPERTIES OF WATER (cont.) 3. Water has a high heat of vaporization: Water absorbs lots of heat as it warms and gives off lots of heat as it cools Reason: hydrogen bonds This lets us keep body temp within certain limits Also lets lakes, rivers, oceans store vast amounts of heat, thus moderating the environment

PROPERTIES OF WATER (cont.) 4. Why ice floats: When most liquids get cold, their molecules move closer together and eventually freeze solid Water behaves differently: As it cools down, the molecules move farther apart, eventually forming ice A chunk of ice has fewer molecules than an equivalent amount of liquid water It floats because it is less dense than liquid water

Figure 2.15

ACIDS, BASES, SALTS Acid A substance which dissociates into one or more H+ ions and one or more negative ions or an acid can be defined as a proton donor HCl H+ + Cl- Examples: hydrochloric acid, lemon juice, vinegar, tomato juice, coffee

ACIDS, BASES, SALTS Base A substance which dissociates into one or more hydroxide ions (OH-) or a base can be defined as a proton acceptor NaOH Na+ + OH- Example: Sodium hydroxide

ACIDS, BASES, SALTS Salts These dissociate when dissolved in water Acid + base = a salt + water Example: HCl + KOH = KCl + H2O

pH Scale 01 2 3 4 5 6 7 8 9 10 11 12 13 14 Acidic Neutral Basic 01 2 3 4 5 6 7 8 9 10 11 12 13 14 Acidic Neutral Basic Water is neutral (H+, OH-) pH = 1/log [H+] negative log of hydronium (H+) ion concentration (molarity)

Figure 2.17

CHEMICAL REACTIONS Two parts: reactant and product Synthesis Reaction (Anabolism) Atoms or molecules combine, form new bonds A + B = AB Decomposition Reaction (Catabolism) Chemical bonds break here AB = A + B Exchange Reaction Part synthesis; part decomposition AB + CD = AD + BC