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Chemical Basis of Life Basic Chemistry All matter on Earth is made from approx. 100 elements!! Element-a substance that cannot be broken down by chemical processes into simpler substances – Atom-smallest form of an element Compounds A substance that is made of two or more elements chemically combined in definite proportions – Ex: H2O (water) Always two hydrogen molecules for every one Oxygen molecule Organic Compounds Generally associated with living things All contain Carbon!! Structure of an Atom Protons: positively charged particles Neutrons: neutral particles Electrons: negatively charged particles Periodic Table: Atomic Number = the number of protons H = 1, O=8 Atom: Just the facts Atoms of the same element have the same number of protons and electrons Atoms of the same element can have different numbers of neutrons = Isotopes Radioactive: nucleus splits apart spontaneously (gives off energy) – Releases charged particles and radiation Electrons Orbit around the nucleus in specific energy levels – First energy level requires 2 electrons – other energy levels require 8 electrons Electrons (cont’d) Atoms are most stable when their outer energy levels are “full” Atoms will gain or lose electrons in order to fill the outermost level The remaining atom is called an ion Ions Atoms with a positive or negative charge Losing electrons = positive Gaining electrons = negative Chemical bonds Attractions that hold two or more atoms together – Whenever a chemical bond is formed or broken energy is absorbed or released (heat) Three types: Ionic, Covalent, Hydrogen 1. Ionic Bonds Formed between ions with opposite charges resulting in a compound that has no electrical charge IMPORTANT—electrons are lost by one element and gained by another EX: NaCl (table salt) 2. Covalent Bonds Electrons are not gained or lost… they are shared (ex: water) Covalent bonds create molecules! See pages 40 & 41 Polar Molecules Molecules in which electrons are not shared equally between atoms This causes the molecules to have one slightly positive end and one slightly negative end O Figure 2.12 + H H + Hydrogen Bonds Bonds that occur between molecules containing hydrogen Important—properties of water and the chemistry of living things! Opposites attract + O H + H + + Chemical formulas Shows what type of atoms are in a compound or molecule – Empirical formula: shows simplest proportions of atoms in compounds – Structural: shows number and type of atoms as well as how they are bonded – Molecular: Shows number and types of atoms (most common) Simple Variety Not all living things are as complex as humans Most living things are made up of only four kinds of chemicals… 1. Carbohydrates “chemical energy” – Sugars, starches, and cellulose – Store energy and provide shape Carbohydrates (cont’d) Three types of sugars 1. Monosaccharides 2. Disaccharides 3. Polysaccharides Complex Carbohydrates What do we use them for??? Energy storage! In the form of glycogen (in muscles and liver) Plants store energy also! In the form of starch! (potatoes, wheat, grains) Cellulose Most abundant molecule on Earth Storage for simple sugars Found in desks, paper, pencils, etc. 2. Lipids “long term energy storage” Fats, oils, waxes, steroids Lipids are converted into fat when too many are consumed Lipids are important!! Cell membranes are made of phospholipids Waxes repel water – Fruits and leaves retain water – Ducks are waterproof 3. Proteins Main control system in your body Large complex molecules composed of amino acids – Only 20 amino acids combine to make up the countless numbers of proteins that make up all living things! The Importance of Protein! Important for movement, structure, regulation, transport, nutrition, defense Insects use proteins called pheromones to communicate 4. Nucleic Acid Makes you who you are! Large, complex molecules that contain genetic information DNA Deoxyribonucleic acid – Carries all of the instructions needed to make an organism Heredity: the passing of genetic information from parent to offspring RNA Ribonucleic Acid – Uses DNA’s instructions to make proteins Chemical Reactions The breaking of bonds to change one or more substances Ex: remember the cracker, as the saliva broke down the starch the cracker began to have a sweet taste! How did it do that???? Remember starch is a polysaccharide (carbohydrate) – The saliva breaks down the polysaccharide into simple sugars! You were a part of a chemical reaction!! Chemical Reaction One or more substances is changed into a new substance by the breaking or forming of chemical bonds Chemical Equation Describes what happens in a chemical reaction (reactants) (products) C6H12O6 + 6O2 6H2O + 6CO2 + energy (Glucose) Chemical Reactions & Energy 1. 2. All chemical reactions are either… Absorb energy = endothermic Release energy = exothermic -The energy that is given off when a substance is formed is equal to the energy needed to break it down!! How to speed up a chemical reaction… 1. 2. Temperature—an increase in temperature = an increase in chemical reaction rate (why??) Catalyst—a substance that speeds up or slows down a reaction (it is not used or changed in the reaction) Catalyst All living organisms contain catalysts = enzymes! – An enzyme is a protein catalyst that speeds up the chemical reactions within an organism by reducing the amount of activation energy needed Pg. 44 Figure 2.15 Enzyme Facts Names usually end in –ase Have a specific shape so they only fit one substrate (lock & key) They are never actually used up in the reaction Allow reactions to occur in an organisms without increasing the organism’s temperature. Enzyme Specifics A substrate bonds to an enzyme at the active site. Once the enzyme and substrate are bonded together the enzyme changes shape to ensure the substrate will stay attached = induced fit The enzyme + substrate = E-S complex 1. 2. 3. 4. What are enzymes made out of? What do enzymes do? Molecules that can bind with enzymes are called_________. Why does heating an enzyme change its function? 1. 2. 3. 4. What enzyme broke down H2O2? Where was the enzyme located? What were the products of the reaction? What are enzymes made out of? Chemistry in Life Processes How does the food you eat keep you warm? – Food releases energy when it breaks down chemically, some is in the form of heat – energy is stored in the chemical bonds of the food we eat—it is released by chemical reactions (digestion) Major life processes Metabolism Communication Reproduction Homeostasis Growth and Repair Metabolism The combination of all of the chemical changes that takes place in an organism – Organisms break chemical bonds (digestion) in compounds to release energy – Plants and some organisms can use sunlight to make energy-rich compounds – – – Products of chemical reactions = heat and wastes To grow and develop, cells of organisms must make new carbohydrates, proteins, and lipids—also to make repairs Regeneration-the process of growing back a lost body part Homeostasis Tendency of an organism to maintain stable internal conditions – Ex: sweat to cool body, panting Communication Internal – neurotransmitters Feedback loop- series of reactions that help maintain homeostasis by controlling chemical reactions Pheromones—insects use this protein to communicate(ants form a line to food) Water and Solutions Life processes depend on the properties of water and the characteristics of solutions – Solution: uniform mixture of 2 or more substances; cannot distinguish between the substances Water and Solutions (cont’d) Solute: the dissolved substance in a solution – Solvent: the dissolving substance Ex: Ice tea = solvent Sugar = solute -Suspension: mixture that separates upon standing – Water-the universal solvent Water will form a solution with most ionic compounds Why???? Because it is a polar molecule! (partial charges) Water Cohesion—sticking together Expansion—water expands when it freezes….allowing it to float Why is that important??? Allows pond-dwelling organisms to survive Acids, Bases, and Salts When ionic compounds form solutions the compound breaks apart and releases ions – Acid: releases H+ (hydrogen)ions Ex: orange juice, HCl, vinegar HCl H + Cl – Base: releases OH(hydroxide)ions Ex: NaOH (sodium hydroxide), soaps, ammonia, baking soda NaOH Na + OH – Salt: releases ions other than H+ and OHEx: NaCl (table salt) NaCl Na + Cl When water breaks apart (disassociates) in a solution it releases both H+ and OH- ions = Neutralization reaction NaOH + HCl H2O + NaCl (base) (acid) (water) (Salt) pH scale Measure of the concentration of H+ ions in a solution 1 2 3 4 ACID 5 6 7 8 9 10 11 12 13 14 Neutral BASE So, what mechanism keeps our pH at 7.4? Why is this important??? Burning fuels such as coal, oil, and gasoline releases sulfur and nitrogen compounds into the air What’s also in the air?? Water!! Acid Rain When these things mix H+ ions are released…causing the rain to become acidic Acid rain has a pH of less than 5.6 Destroys minerals in the soil vital to plants…no plants no people Decreases the Ph in lakes…killing aquatic life Page 54 – Questions 1-5 – Write the answers Tell me all you know about enzymes and the liver lab. – What is an enzyme? Why does it have an active site? What enzyme did we use in the lab? What substrate did it break down? Etc… Read “The Molecules of Life” – Answer post test questions 1-11