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Transcript
Chapter 2 The Chemistry of Life Section 2-1 The Nature of Matter Objectives What three subatomic particles make up atoms? How are all of the isotopes of an element similar? What are the two main types of chemical bonds? Atoms Submicroscopic units of matter Smallest unit of all physical material Structure of Atoms Atoms Key Concept: Atoms Are Made of Subatomic Particles Protons Positive Charge Neutrons Neutral Charge Electrons Negative Charge Protons Positively Charged Found In The Nucleus Strongly Bound to Neutrons Have the Same Mass as a Neutron Neutrons Carry NO Charge – NEUTRAL Charge Found In The Nucleus Strongly Bound to Protons Have the Same Mass as a Proton Electrons Negative Charge 1/1840 the Mass of a Proton Constantly Circling The Nucleus Each Atom has the Same Number of Protons and Electrons Electrons Shells correspond to energy levels 1st shell holds max of 2 electrons Every other shell holds up to 8 electrons Elements that make up 95% of living organisms (by weight) C H N O P S Carbon Hydrogen Nitrogen Oxygen Phosphorus Sulfur Elements Pure Substance Containing Only ONE Type of Atom Atomic Number = Number of Protons Atomic Mass = Number of Protons & Neutrons Helium Isotopes Elements that contain more Neutrons than Protons are Isotopes. Identified by their Mass Numbers Chemical Properties Remain Unchanged Number of Electrons Don’t Change Radioactive Isotopes Nuclei are Unstable They Break Down at a Constant Rate Over Time Can be used to calculate age Isotopes of Carbon Molecules and Compounds Molecules form when two or more atoms bond together (example: O2) Compounds form when two or more different elements bond together (H2O) Chemical Compounds A Substance Formed By The CHEMICAL Combination of Two or More Elements Radically Changes The Chemical Properties Of The Elements Involved: Na Cl NaCl = Explosive, Water (Stored Under Oil) = Poison Gas = Salt – Required for life (you eat it daily) Chemical Bonding Ionic Bonding One or More Electrons Transferred Changes The Atoms Charge NaCl Ionic Bonds One atom donates electron to other atom NaCl as a Crystal NaCl NaCl in Solution Na+ Cl - Chemical Bonding Covalent Shared Bonding Electrons Single, Double, Triple Bonds Possible May Cause A Shift of Electron Cloud Resulting In Molecules That Are Polar Water Covalent Bonds H2 Atoms share outer electrons Covalent Bonding Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Electron Model H H Structural Formula H H Molecular Formula H2 a. Hydrogengas A single covalent bond results from sharing one pair of electrons. Covalent Bonding Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. O O O O O2 b. Oxygen gas A double covalent bond results from sharing two pairs of electrons. Water The POLAR Molecule Positive Pole Negative Pole Polar Covalent Bonds If the sharing between two atoms is unequal, the covalent bond is described as polar. Water is an example of a polar molecule Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Electron Model Ball-and-stick Model Space-filling Model Oxygen attracts the shared electrons and is partially negative. – O O O H H H H 104.5° H + H + Hydrogens are partially positive. a. W ater (H2O) Van der Waals Forces Polar Molecules Stick Together Like Little Magnets NOT Strong Like Ionic & Covalent Bonds But Strong Enough For A Gecko ???? The Gecko’s Foot The Water Molecule Neutral All Charge Molecules Are Neutral The Water Molecule Polarity A water molecule is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms. (—) (+) Hydrogen Bonds Polar water molecules act like magnets and attract each other Hydrogen Bonds The attraction of the Hydrogen end (+) of one molecule for the Oxygen end (-) of another water molecule. They are the strongest bonds that can form between molecules Hydrogen Bonds Cohesion The attraction between molecules of the same substance (e.g. water). Allows some insects and spiders to walk on water. Adhesion Attraction between molecules of different substances Responsible for Capillary forces in plants Solutions & Suspensions Water is usually part of a mixture. There are two types of mixtures: Solutions Suspensions Solution Ionic compounds disperse as ions in water Evenly distributed SOLUTE Substance that is being dissolved SOLVENT Substance into which the solute dissolves Solution Properties of Water Water is a solvent. A solution contains dissolved substances, which are then called solutes. Hydrophillic molecules attract water Hydrophobic molecules do not attract water. Suspensions Substances that don’t dissolve but separate into tiny pieces. Water keeps the pieces suspended so they don’t settle out. Properties of Water Water has high heat capacity(heat needed to raise or lower temperature) • A calorie is the amount of heat energy needed to raise the temperature of 1g of water 1°C. Modulates temperature in living bodies Keeps the temperatures on earth stable Acids, Bases & pH 1 water molecule in 550 million naturally dissociates into a Hydrogen Ion and a Hydroxide Ion H2O H+ Hydrogen Ion Acid + OH - Hydroxide Ion Base The pH Scale Indicates the concentration of H+ ions Ranges from 0 – 14 pH of 7 is neutral pH 0 – 6.99 is acid H+ pH 7.01 – 14 is basic OH Each pH unit represents a factor of 10 change in concentration Acids Strong Acid = pH 1-3 H+ Bases Strong Base = pH 11 – 14 OH- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. pure water, tears Buffers Weak acids or bases that react with strong acids or bases to prevent sharp, sudden changes in pH. Buffers and pH A buffer is a chemical or combination of chemicals that keep pH within normal limits. Bicarbonate ions (HCO3-) and carbonic acid (H2CO3) found in human blood buffers the pH to 7.4 Buffers and pH H2O + CO2 H2CO3 H2CO3 H+ + HCO3H+ + HCO3- H2CO3 Excess OH- combines with H+ to form H2O Together these reactions keep the blood at a pH between 7.3 and 7.5 Buffers and pH Decline in pH can cause coma Rise in pH called alkalosis can also cause coma 7.8 can result in tetany – prolonged muscle spasm The Chemistry of Carbon Carbon 4 Valence Electrons Bonds with Hydrogen, Oxygen, Phosphorus, Sulfur, Nitrogen Other Carbon Atoms General Characteristics of Biological Molecules Carbon based Interact by means of functional groups Assembled or disassembled by adding or removing water The Chemistry of Carbon Methane: Single Bonds Acetylene: Triple Bonds The Chemistry of Carbon Butadiene: Double Bonds Benzene: Ring Bonding The Chemistry of Carbon Covalent Bonds Single, Double, Triple But Always Four (4) Bonds No Other Element is so versatile. Millions of Different Structures Changing Molecules Assembling molecules Growth and repair Producing molecules essential for chemical reactions to take place Disassembling molecules Digestion Providing molecules that can enter cells Assembly: Dehydration Synthesis Monomers = one building block Polymers = two or more monomers linked by covalent bonds Disassembly: Hydrolysis Hydrolysis is opposite of dehydration Covalent bonds broken with addition of H2O Energy in bond is released Macromolecules Means “Giant Molecules” Each Macromolecule Is Constructed of Thousands to Hundreds of Thousands of Smaller Molecules Called Monomers. Macromolecules Monomers Are The Basic Building Block (Smallest Unit) of Any Macromolecule Glucose Nucleotides Amino Acids Monomers Builds Cellulose Builds DNA & RNA Builds Proteins Combine And Become Polymers Through Polymerzation Groups of Macromolecules Carbohydrates Lipids Nucleic Acids Proteins Carbohydrates C:H:O in ratio of 1:2:1 Main source of energy Sometimes structural molecules Cellulose Sugars, starches Mono & Polysaccharides Carbohydrates Key Concept: 1. 2. Living Things Use Carbohydrates As Their Main Source of Energy! Plants and some Animals Use Carbohydrates For Structural Purposes: e.g. Cellulose Carbohydrates - Monosaccharides Single Sugars Glucose (Universal) Galactose (Milk) Fructose (Fruits) Carbohydrates - Polysaccharides Macromolecules from Monosaccharides Glycogen (Animals) Carbohydrates - Polysaccharides Macromolecules from Monosaccharides Starch (Plants) Cellulose (Plants) Carbohydrates - Disaccharides Sucrose: Maltose: Lactose: Some Carbohydrates are Used for Structure Cellulose – plant cell wall material Chitin – in insects, fungi Lipids (fats) Key Concept: Lipids Can Be Used To Store Energy. Some Lipids Are Important Parts Of Biological Membranes And Waterproof Coverings Lipids (fats) Made Mostly of Carbon & Hydrogen Not Water Soluble Catagories of Lipids Include: Fats Oils Waxes Steroids Fats Non-polar & insoluble • Two types of subunits Long term energy storage – Glycerol More energy than equivalent – Fatty acids carbohydrates Lipids (fats) Formed from Glycerol & Fatty Acids Lipids (fats) Saturated Each Carbon Atom In The Fatty Acid Chain Is Joined To Another Carbon By A Single Bond That Means The Macromolecule Contains The Maximum Number of Hydrogens Solid At Room Temperature Butter, Margarine, Lard, Shortening, etc. Triglycerides Saturated – carries as many H as possible Lipids (fats) Unsaturated One Or More Carbon to Carbon Bond(‘s) Is/Are Multiply Bonded These Lipids Are Liquid At Room Temperature Olive Oil, Peanut Oil, Other Cooking Oils Triglycerides Unsaturated – double bond replaces H Polyunsaturated – more than 1 double bond Differences in Fats & Oils Polyunsaturated - liquid at room temp Plant oils Fish oils Saturated-solid at room temp Animal fats Tend to raise blood cholesterol Phospholipids Phosphate group replaces a fatty acid Key component of cell membrane Steroids Examples include cholesterol and sex hormones Important for membranes Nucleic Acids Key Concept: Nucleic Acids Store & Transmit Hereditary or Genetic Information Every Life Form Uses The Same Nucleic Acids Nucleic Acids Macromolecules with C, H, O, N; P Polymers of Nucleotides: 5 Carbon Sugar +Phosphate Group + Nitrogen Base 5 Carbon Sugars RNA Ribonucleic Acid DNA Deoxyribonucleic Acid Summary of DNA and RNA structural differences DNA RNA Sugar is deoxyribose Bases include A, T, C and G Double stranded Sugar is ribose Bases include A, U, C and G Single stranded Hydrogen bond bases Adenine (A) Thymine (T) (DNA only) backbone Guanine (G) a. DNA structure with base pairs: A with T and G with C Cytosine (C) b. RNA structure with bases G, U, A, C Uracil (U) (RN only) 5 Carbon Sugars DNA Deoxyribose Sugar RNA Ribose Sugar The Only Difference Proteins Key Concept: Some Proteins Control the rate of reactions and Regulate Cellular Processes. Some Form Bones & Muscles. Others Transport Substances In/Out of Cells or Help Fight disease Proteins Macromolecules with C, H, O, N Polymers of Amino Acids Compounds with an Amino Group (NH2) and a Carboxyl Group (-COOH) on the other end Allows 20 bonding between any amino acid AA’s in nature Amino Acid “R” Groups Each Amino Acid Is Different in the R-Group Amino Acid “R” Groups Some Polar, some Non-Polar Some Acidic, some Basic Some contain Carbon Rings Protein Levels of Structure Primary structure = amino acid sequence Secondary structure = shape Coils Folds Tertiary structure = complex shape caused by hydrogen bonds Quaternary structure= final structure formed when two or more different proteins bond together Levels of Organization 1. 2. 3. 4. Sequence of Amino Acids Amino Acid Twists & Folds Within Chain Twists & Folds of Chain Itself Multiple Protein Chains May Be Necessary To Make An Active Protein Protein Shape Is Critical To Function Summary of the macromolecules Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Organic molecules Examples Monomers Functions CH2OH Monosaccharides, disaccharides, Carbohydrates Polysaccharides (starch, glycogen, cellulose, chitin) O H OH Immediate energy and stored energy; structural molecules H H HO OH H OH Glucose H Lipids Fats, oils, wax, phospholipids, steroids H H H H H C C C C C C H H H H H O H C OH H C OH HO H C OH R Fatty acid H Glycerol Proteins Structural, enzymatic, carrier, hormonal, contractile amino group H2N H C acid group COOH R group Long-term energy storage; membrane components Support, metabolic, transport, regulation, motion Amino acid phosphate P Nucleic acids DNA, RNA base C O S Nucleotide Storage of genetic information Chemical Reaction Key Concept: Chemical Reactions Always involve breaking bonds of Reactants and the formation of new bonds to form in products Chemical Reaction Process that changes one set of chemicals into another set of chemicals. Reactants Products Transport of CO2 CO2 Is NOT Very Soluble In Water When CO2 Enters Your Bloodstream It Reacts With Water To Form Carbonic Acid H2CO3 Which Increases Your Bloods Carrying Capacity – Then, The Reverse Happens In Your Lungs Transport of CO2 Tissue to Blood CO2 + H20 H2CO3 Blood to Lung H2CO3 CO2 + H20 Energy In Reactions Energy is released or absorbed every time chemical bonds form or break. Energy changes determine whether a reaction will take place. Energy In Reactions Key Concept: Reactions That Release Energy Often occur spontaneously Chemical Reactions That Absorb Energy Will Not Occur Without A Source Of Energy Energy Releasing Reaction 2H2 + O2 2H2O Activation Energy Energy needed to start a reaction Activation Energy Reactions That Absorb Energy Will not occur without a source of energy e.g. Decomposition of water 2H2O 2H2 + O2 Enzymes Key Concept: Cells Use Enzymes To Speed Up Chemical Reactions That Take Place In Cells Often act as Catalyst Speed up the rate of reaction Lower activation energy Enzyme Effects Enzyme-Substrate Complex Enzymes Provide A Site Where Reactants Can Be Brought Together To React. Reduces The Energy Needed For The Reaction Reactants AKA Substrates Substrates bind to active site Lock & Key, VERY specific Regulation of Enzymes pH Temperature Cells contain “switch” proteins