Welcome to Biology 160! Welcome to Biology 160! Welcome to Biology 160! The Molecules of Life. Draw Biology. We re Made of Atoms?!

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1 Welcome to Biology 160! Today s Agenda: 1. Introductions 2. Syllabus and Course Website 3. Getting to Know You! 4. Group Discussions 5. Chemistry for Biologists? Welcome to Biology 160! Syllabus and Course Website: Please bookmark the site and let me know if you have problems with any of the content! Reminders: Print and read Lab 1 before class Friday! Welcome to Biology 160! Something more fun: Draw Biology. Be messy! Be creative. What does biology look like to you? Ask someone in your group to be ready to share the ideas with the class! The Molecules of Life You Try: Part 1- Brainstorming We re Made of Atoms?! Ex: Hydrogen and Helium Atoms What are the essential components of atoms? What makes the atoms of one element different from the atoms of another element? electron proton neutron HYDROGEN HELIUM The Number of Protons determines the ELEMENT a given atom is part of. 1

2 The Molecules of Life Elements may be described by their atomic number. The atomic number is the number of protons in an atom. The Molecules of Life Elements may also be described by their atomic mass. The atomic mass is the number of protons plus the number of neutrons in an atom. Isotopes Quick Concept Check: Part 2 Isotopes are atoms of an element with different numbers of neutrons (different mass numbers) The Molecules of Life Atoms may be linked together to form compoundstwo or more elements in a fixed ratio Next: How and why do bonds form? Electron Vacancies Unfilled shells make atoms likely to react Hydrogen, carbon, oxygen, and nitrogen all have vacancies in their outer shells! CARBON 6p+, 6e - NITROGEN 7p+, 7e - HYDROGEN 1p+, 1e - 2

3 Electron Vacancies: Another View Important Bonds in Biological Molecules: 1. Ionic Bonds 2. Covalent Bonds 3. Hydrogen Bonds 1. Ionic Bonds: Ion Formation Atom has equal number of electrons and protons - no net charge Atom loses electron(s), becomes positively charged ion Atom gains electron(s), becomes negatively charged ion 1. Ionic Bonds: Forming a Bond One atom loses electrons, becomes positively charged ion Another atom gains these electrons, becomes negatively charged ion Charge difference attracts the two ions to each other 1. Ionic Bonds: The Formation of NaCl Sodium atom (Na) Outer shell has one electron Chlorine atom (Cl) Outer shell has seven electrons Na transfers electron to Cl forming Na + and Cl - Ions remain together as NaCl SODIUM ATOM 11 p + 11 e - SODIUM ION 11 p + 10 e - Formation of NaCl electron transfer 7mm CHLORINE ATOM 17 p + 17 e - CHLORINE ION 17 p + 18 e - Fig. 2.10a, p. 26 3

4 2. Covalent Bonding Atoms share a pair or pairs of electrons to fill outermost shell Nonpolar Covalent Bonds Atoms share electrons equally Nuclei of atoms have same number of protons Example: Hydrogen gas (H-H) Polar Covalent Bonds Number of protons in nuclei of participating atoms is NOT equal Electrons spend more time near nucleus with most protons Water - Electrons more attracted to O nucleus than to H nuclei 3. Hydrogen Bonding Molecule held together by polar covalent bonds has no NET charge However, atoms of the molecule carry different partial charges Atom in one polar covalent molecule can be attracted to oppositely charged atom in another such molecule Weak, but biologically important! Examples of Hydrogen Bonds one large molecule Special Properties of Water another large molecule You Try! Part 3 a large molecule twisted back on itself 4

5 The Result: Temperature- Stabilizing Effects Liquid water can absorb lots of heat before its temperature rises WHY? Much of the added energy disrupts hydrogen bonding rather than increasing the movement of Evaporation of Water Large energy input can cause individual of water to break free into air As break free, they carry away some energy (lower temperature) Evaporative water loss is used by mammals to lower body temperature (Homeostasis!) Water Cohesion Hydrogen bonding holds in liquid water together Creates surface tension Allows water to move as continuous column upward through stems of plants Water Is a Good Solvent Ions and polar dissolve easily in water When solute dissolves, water cluster around its ions or and keep them separated Hydrogen Ions: H + Unbound protons Have important biological effects Form when water ionizes 5

6 The ph Scale The ph Scale Measures H+ concentration of a fluid Change of 1 on scale means 10X change in H + concentration Highest H + Lowest H Acidic Neutral Basic Organic Compounds Hydrogen and other elements covalently bonded to carbon Carbohydrates Lipids Proteins Nucleic Acids Carbon s Bonding Behavior How many electrons are in carbon s outer shell? How many electrons does this shell hold? How many covalent bonds will carbon form? Molecule Class 1: Carbohydrates Familiar Polysaccharides Monosaccharides (simple sugars) glucose fructose Disaccharides (two monosaccharides bonded together) + H 2 O Polysaccharides (complex carbohydrates) sucrose 6

7 Class 2: Lipids Most include fatty acids Fats Steroids (like cholesterol) Tend to be insoluble in water (hydrophobic!) An Aside: You Know These Fats! BOARD OF HEALTH VOTES TO PHASE OUT ARTIFICIAL TRANS FAT FROM NEW YORK CITY S RESTAURANTS Health Department Facilitates Restaurant Implementation, Ensures Phased Removal of Artificial Trans Fat from Restaurants by July 1, 2008 NEW YORK CITY December 5, 2006 Restaurants are a major source of artificial trans fat, but customers currently have no practical way to know whether food they eat contains it. Today, the New York City Board of Health voted unanimously to make New York City even healthier by requiring that all City restaurants remove artificial trans fat over the next 18 months. Proteins are polymers (long chains) of amino acids. We use 20 different amino acids to build our proteins. Class 3: Proteins Primary Functions: Energy carriers Class #4: Nucleotides Building blocks for nucleic acids (DNA & RNA) 7