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Name:______________________ Biology CPA – Chapter 2 The Chemistry of Life Study Guide The Nature of Matter An atom is: the simplest particles of an element that retains all the properties of that element. Subatomic particles Electrical charge Found in Protons + Nucleus Neutrons Neutral Nucleus Electrons orbital Diagram and label an Oxygen Atom: Oxygen has how many: Protons 8 Neutrons 8 Electrons 8 Elements and Isotopes An element is a substance that cannot be broken down chemically into simpler kinds of matter. Atomic Number & Atomic Mass The Atomic number of an atom is equal to: # protons The Atomic mass of an atom is equal to: # protons and # of neutrons An isotope are atoms of the same element that have a different # of neutrons Chemical Compounds A compound is made up of atoms of two or more elements in fixed proportions Examples of compounds: Compound: H20 Made of elements: Hydrogen, oxygen Chemical Bonds Ionic Bonds Formed by Explain how ions are formed Draw an example of a substance that is formed by ionic bonding NaCl Sodium, chloride the attractive force between oppositely charged ions When an atom gains or loses an electron Covalent Bonds Formed by Sharing of electrons Draw an example of a substance that is formed by covalent bonding Properties of Water A water molecule is polar because of uneven distribution of electrical charges on a molecule Draw one water molecule here showing polarity: Explain why we were able to float a paper clip on the surface of water. What type of bonds were present that allowed this to happen? Hydrogen bonds formed between water molecules are strong which produces a tension on the surface of the water. What does cohesion mean? What does adhesion mean? How are they important for life? Cohesion is the attractive force that holds molecules of a single substance together Adhesion is the attractive force between two particles of different substances They are important for life because they allow capillary action to occur which is the attraction between molecules that results in the rise of the surface of a liquid when in contact with a solid Water is the universal solvent. What does this mean and why is it important? Water is able to dissolve or break down compounds into their components. Important because we need ions to carry out important life processes. (Na+ and electrical impulses) Explain how the density of ice is important for life? Water expands when frozen which causes ice to be less dense than liquid water. This is important for life because ice floats and organisms wouldn’t survive if bodies of water froze from the bottom up. Acids, Bases and pH The pH scale The pH scale measures the concentration of H+ and OH- ions in solution. The pH scale ranges from 1 to 14. A pH of 7 is considered to be neutral. An acid is any substance that forms Hydrogen ions (H+) in solution. A base is any substance that forms Hydroxide ions (OH-) in solution. Chemical Reactions A chemical reaction occurs when one or more substance change to produce one or more different substances The elements or compounds that enter into a chemical reaction are called the reactants. The elements or compounds that are produced by a chemical reaction are called the products. Chemical reactions always involve breaking bonds in the reactants and creating new bonds in the products. Energy in Reactions Define energy: The ability to do work Solid Liquid Gas compact More freely Free moving Fixed Volume Fixed volume Fills container Phase of Matter Movement of atoms Volume ENERGY must be added or removed for a substance to change states of matter. Label the following equation: Reactant + Reactant Product An example of a Reduction/Oxidation or REDOX reaction is: What is “activation energy?” Activation Energy is the amount of energy needed to start a chemical reaction Catalysts Some chemical reactions that are necessary for life occur too slowly or have a high activation energy. A catalyst speeds up the rate of the reaction by lowering the amount of activation energy needed to start the reaction Catalysts work by lowering the activation energy needed to get a reaction going. Enzyme Action Substrates are substances with which an enzyme binds to chemically change it. Use the following terms to identify the components of the following enzyme reaction. Explain why we can describe the enzyme-substrate complex as a “lock & key.” Enzymes are very specific and will only work on one specific type of substrate, much like only one key will fit into a lock. The site where the substrate binds to the enzyme is called the active site. Name two ways that enzyme activity is important in humans. Digestion, immune system