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Mrs. Williams Biology Honors Semester One CHAPTER 2: THE CHEMISTRY OF LIFE Section 1: Atoms, Ions, and Molecules Atoms are the smallest unit of an element Three particles Protons (+ charge) Electrons (- charge) Neutrons (no charge) Nucleus contains protons and neutrons Elements Elements are pure substances consisting of only one type of atom Cannot be broken down further! Listed in the periodic table Atoms of each element differ by the # of protons Isotopes Isotopes are atoms of an element with different number of neutrons Atomic # is the same; mass # is different Most have same chemical properties Radioactive Isotopes Radioactive isotopes have unstable nuclei that break down at a constant rate over time Uses for radioactive isotopes Dating of rocks and fossils Treating cancer Killing bacteria on food Trace movements of substances within the body Ions and Bonding Ions are formed when an atom gains or loses an electron Ionic bonds vs. covalent bonds Read on pages 38 & 39 about ionic and covalent bonding to yourself Compare and contrast the two bonding types with your table partner Bonding Ionic Covalent Forms through the Forms when atoms share a electrical force between oppositely charged ions Ex: NaCl pair of electrons Generally very strong bonds Depending on the # of electrons, two atoms may form several covalent bonds Ex: CO2 - Fig. 2.4 Sodium (Na+), a positively- charged ion is attracted to chlorine (Cl-), a negativelycharged ion. Chemical Compounds A chemical compound is a substance of two or more elements in definite proportions Different chemical properties than the original elements Compound composition given in chemical formula For example: NaCl and H2O Chemical Reactions Chemical reactions are the breaking and forming of chemical bonds Reactants- original elements or compounds Products- ending elements or compounds Section 2: Properties of Water Water – H2O Polar molecule Has a region with a slight positive charge and a region with a slight negative charge (page 40 - fig. 2.5) Hydrogen bond An attraction between a slightly positive hydrogen atom and a slightly negative atom (often O or N) Properties Related to Hydrogen Bonds – page 41 1. High Specific Heat Water resists changes in temp; very important in cells! 2.Cohesion The attraction among molecules of a substance Caused by hydrogen bonds Produces surface tension 3. Adhesion Attraction among molecules of different substances Water is a Solvent! Page 42 Solution Mixture of substances that is the same throughout (a homogenous mixture) Has two parts Solvent – the substance that is present in the greater amount and that dissolves another substance Solute – a substance that dissolves in a solvent Acids and Bases Some compounds break up into ions (an atom that has gained or lost electrons) when they dissolve in water Acids release a proton (H+) when they dissolve in water Bases remove H+ ions from a solution A solution’s acidity is measured by the pH scale (page 43, figure 2.9) Dissociation of Water pH Scale Scale measuring amount of H+ (really H3O+) Ranges from 0-14 Below 7- acids Higher H+ Above 7- bases Higher OH- 7- Neutral Equal numbers of both Origin Statement – August 7th In your notebook, answer the following WITHOUT USING NOTES: 1. Describe an atom. List all parts and their charges. 2. How do we determine atomic number? 3. What is an isotope? 4. Describe the 3 properties of hydrogen bonding. 5. Acids have a pH between ? and ? Bases have a pH between ? and ? Section 3: Carbon-based molecules Carbon-based compounds A monomer is a basic repeating building block A polymer is many monomers connected together Draw a visual representation of a monomer and polymer! Dehydration Synthesis Building larger molecules from smaller ones (requires energy) Monomer → Polymer Hydrolysis Break down large molecules into smaller ones (releases energy) Polymer → Monomer Carbon Compounds Condensation/Synthesis Polymer Monomer Hydrolysis Carbohydrates Made of C, H, and O in a 1:2:1 ratio Monomers Monosaccharide Examples: glucose, fructose, galactose Dimers Disaccharides Examples: sucrose and lactose Polymers Polysaccharides Examples: starch, glycogen, chitin, and cellulose Carbohydrates Carbohydrates (Starch) Carbohydrates (Glycogen) Carbohydrates (Chitin and Cellulose) Chitin Cellulose Uses for Carbohydrates Provide energy for body functions Used to build nucleic acids Other structural functions Tests for Carbohydrates Benedict’s Test for Simple sugars Iodine Test for Complex Sugars Lipids (Fats & Oils) Made of C, H, and O (phospholipids have P) Triglyceride 1 Glycerol, 3 Fatty Acid Chains Examples: Fats found in adipose tissue Phospholipid 1 Glycerol, 2 Fatty Acid Chains Example: Molecules found in cell membrane Steroid 4 Carbon ring structure Example: cholesterol, testosterone, estrogen, and other hormones Lipids Lipids Lipids Lipids Testosterone Progesterone Cholesterol Uses for Lipids Energy source Padding and insulation Structural Hormones Water-proofing Tests for Lipids Sudan IV Test Sudan IV turns red in the presence of lipids Newspaper Test Lipids leave a translucent spot on newspaper/brown paper bags (think fast food bags) Protein Made of C, H, O, S, and N Monomer Amino acids (20 found in the body; 12 made by you…the others come from foods you eat) Polymer Polypeptide Amino acids are held together by a peptide bond Amino Acid Structure H H3N+ C R COOH Amino Acid Structure Polypeptide H H3N+ C R H COOH H3N+ C R H COOH H 3 N+ C R H COOH H3N+ C R COOH Uses for Proteins Structural – form bones and muscles Enzymes - speed up rates of reactions Transport – Help bring substances into or out of cells Antibodies – Helps fight diseases/immunity Test for Proteins Biuret Test – purple or pink indicates protein Energy of Reactions Reaction Types Energy Releasing Reaction is spontaneous (not fast, necessarily) Activation energy – energy need to get the reaction started At the end of the reaction, energy is released into the environment Energy Absorbing Rxn is not spontaneous Activation energy- energy needed to get the rxn started At end of the rxn, energy is absorbed from environment Energy Reaction Diagrams Enzymes - Intro Catalyst for the reaction (speeds it up) Substrate (reactant) enters the active site of the enzyme to form an enzyme-substrate complex After the rxn, the product leaves The enzyme remains unchanged Enzymes Action of Enzymes Speeds up the reaction by lowering activation energy Enzyme Reaction Rates Rates can be affected by: Temperature pH Amount of enzyme Nucleic Acids Made of C, H, O, N and P Monomer- Nucleotide DNA Phosphate Sugar Sugar - Deoxyribose Nitrogen Bases – A, T, G, C RNA Sugar- Ribose Nitrogen Bases- A, U, G, C Nitrogen Base DNA Nucleotide = Phosphate Purines = Deoxyribose Pyrimidines = Adenine = Thymine = Guanine = Cytosine A=T G=C A G T C Nucleic Acids RNA Nucleotide = Phosphate Purines = Ribose Pyrimidines = Adenine = Uracil = Guanine = Cytosine RNA Structure •Single-stranded Uses for Nucleic Acids They work together to make proteins by storing genetic information ATP Structure Adenine High Energy Bonds Adenosine Ribose Phosphates ADP Structure