Bio 134 Ch. 6
6.1 Atoms, Elements, and Compounds P
Main Idea Matter is composed of tiny particles called atoms
Atom Building blocks of matter
Structure of an Atom Nucleus – the center of the atom where protons and neutrons are located Protons – positively charged particles Neutrons – particles that have no charge Electrons – negatively charged particles located around the nucleus
Inside an Atom
Element A pure substance that cannot be broken down into other substances by physical or chemical means Are made of 1 type of atom
Isotopes Atoms of the same element that have different numbers of neutrons Add the number of protons and neutrons
Compounds Are a pure substance formed when two or more different elements combine H 2 O –2 hydrogens, 1 oxygen
What are 2 characteristics of compounds? 1. Always formed in a fixed ratio –Example: Water – H 2 O – always has 2 H for every 1 O 2. Can only be broken down into specific parts by a chemical reaction
Chemical Bond The force that hold two substances together –Example: water (H 2 O), salt(NaCl), methane (CH 4 )
Chemical Bond They travel around the nucleus in areas called energy levels A partially filled energy level is not stable. Atoms become more stable by losing e- or attracting e- from other atoms
Covalent Bonds a chemical bond that forms when e- are shared
Molecule Substances with covalent bonds –Example: water (H 2 O) Covalent bonds can be single (sharing only 1 pair of e-) double (sharing 2 pairs of e-) or triple (sharing 3 pairs of e-)
Ionic Bond Ion – an atom that has lost or gained one or more electrons and has a positive or negative charge Ionic Bonds – when + charged ions bond with – charged ions
NaCl Ionic Bond
Van der Waals Forces When molecules come close together, the attractive forces between slightly positive and negative regions pull on the molecules and hold them together. The strength of the attraction depends on the size of the molecule, its shape, and its ability to attract electrons
End of 6.1
6.2 Chemical Reactions p
Main Idea Chemical reactions allow living things to grow, develop, reproduce, and adapt
Reactants and Products Chemical reaction – the process by which atoms or groups of atoms in substances are reorganized into different substances -Chemical bonds are broken down or formed
How do you know a chemical reaction has taken place? Color change Production of heat Production of light Formation of a gas, solid, or liquid
Example of a chemical reaction:
Chemical Equations Reactants – the starting products are always on the left side of the arrow Products – the substances formed during the reaction are always on the right side of the arrow Reactants Products
Balanced Equations Law of Conservation of Mass – states that matter can not be created nor destroyed The number of atoms of each element on the reactant side must be equal to the number of atoms of the same element on the products side
Why do we balance chemical equations? Because matter can not be created nor destroyed
Paper Burning Demo
Paper Burning Check… How do we know a reaction took place? What happened when we covered the paper with the glass cover? What was needed in order for the paper to burn?
Energy of Reactions Activation Energy – the minimum amount of energy needed for reactants to form products in a chemical reaction –Example – a candle will not burn until you light the wick, the flame provides the activation energy for the reaction of the substances in the candle
Types of Reactions Exothermic reactions – it releases energy in the form of heat
Types of Reactions Endothermic reactions – it absorbs heat energy
Back to Paper burning… What was the activation energy that started the reaction of the paper burning? Was it an endothermic or exothermic reaction?
Enzymes Catalyst – a substance that lowers the activation energy needed to start a chemical reaction Enzymes – are biological catalysts that speed up the rate of chemical reactions in biological processes
Enzyme Activity
Substrates – the reactants that bind to the enzyme Active site – the specific location where a substrate binds on an enzyme
Substrates and Active Sites
What are the factors that affect Enzyme Activity? pH Temperature Other substances
End of 6.2
6.3 Water and Solutions P
Why is water so important in Biology?
Main Idea The properties of water make it well suited to help maintain homeostasis in an organism
Polar molecule Molecles that have an unequal distribution of charges and have oppositely charged regions Example of polarity – the reason water and oil don’t mix – water is polar and oil is not
Example of polarity – Water and Oil
Hydrogen bond A weak interaction ivolving a hydrogen atom and a F, O, or N atom Is a strong type of van der Waals interaction
Hydrogen Bonding
Mixture Combination of two or more substances in which each substance retains its individual characteristics Examples of mixtures:
Homogeneous mixture A mixture that has a uniform composition throughout Examples:
Solution When all of the components are evenly distributed throughout –Example: saltwater
Solvent The substance in which another substance is dissolved Example: water
Solute The that is dissolved in the solvent Example: salt
Heterogenous mixture The components remain distinct, you can tell what they are individually Example: a salad – has lettuce, vegetables, dressing – each ingredient remains independent
Suspension When a particles in a liquid are not dissolved, and remain moving
Colloid a heterogeneous mixture in which the particles do not settle out –Example – milk – protein and fat don’t settle out
Blood Solution – blood is a solution because it has many dissolved particles in it Suspension – blood is a suspension because it has many particles suspended in it such as cells
Acids and Bases Acid – substances that release Hydrogen ions (H+) when dissolved in water Base – substances that release hydroxide ions (OH-) when dissolved in water
pH The measure of concentration of H+ in a solution pH of pure water is 7 (neutral) pH of lower than 7 are acidic –have more H+ pH of higher than 7 are basic –-have more OH-
pH Scale
Buffers Mixtures that can react with acids or bases to keep the pH within a particular range In cells, buffers keep the range between 6.5 and 7.5 In blood, buffers keep the range at about 7.4
End of 6.3
6.4 The Building Blocks of Life p
How does Chemistry relate to Biology?
Main Idea Organisms are made of carbon-based molecules
Organic Chemistry Carbon can form covalent bonds with 4 other atoms, including other carbons Can form straight chains, branched chains, and rings
Macromolecules large molecules that are formed by joining smaller organic molecules together
Polymers Molecules made from repeating unit of identical or nearly identical compounds linked together by a series of covalent bonds Poly means many
P. 167 Use table 6.1 and list examples and functions of the 4 biological macromolecues
Carbohydrates Compounds composed of carbon, hydrogen, and oxygen in a ratio of 1O, 2H, 1C (CH 2 O) n – n is the number of units in the chain
Carbohydrate functions Energy source – monosaccharide, disaccharide, sucrose (table sugar), lactose (in milk) Structural support –in plants, cellulose provides support in cell walls –In animals Chitin is a polysaccharide that is the main component in the hard outer shell of shrimp, lobsters, and some insects and fungi
Lipids Molecules made mostly of carbon and hydrogen that make up fats, oils, and waxes Primary function is to store energy –In animals, stored in fat cells –In plants, used as waxy coating on some leaves
p. 169 Use your textbook to describe the following: –Saturated fats –Unsaturated fats –Polyunsaturated fats
Types of fats –Saturated fats - Lipids that have tail chains with only single bonds between the carbon atoms –Unsaturated fats - Lipids that have at least one double bond between carbon atoms –Polyunsaturated fats - Fats with more than one double bond in the tail
Other Lipids Phospholipid - Responsible for the structure and function of the cell membrane, serves as a barier in biological membranes Steroid – examples: cholesterol and hormones such as estrogen and testosterone
Proteins A compound made of small carbon compounds called amino acids
Amino acids Small compounds that are made of carbon, nitrogen, oxygen, hydrogen, and sometimes sulfer
Amino Acid Structure Have a central carbon atom An amino group (H 2 N) A H atom A variable group – this makes each one different (20 different groups)
3-D structure Proteins have up to 4 levels of structure: –Primary structure - # of amino acids in a chain and the order they are in –Secondary structure – folds into a uinque 3-d shape (helix and pleat) –Tertiary structure – globular or long fibers –4 th level – combining with other proteins
Nucleic Acid Complex macromolecules that store and transmit genetic information Made of smaller nucleotides
Nucleotides Composed of carbon, nitrogen, oxygen, phosphorus, and hydrogen atoms 6 major nucleotides
DNA and RNA Nucleic acids found in living organisms
ATP The storehouse of chemical energy that can be used by the cells
End of 6.4
End of Ch. 6