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Chapter 6 Chemistry in Biology 6.1 Atoms, Elements, and Compounds Atoms Chemistry is the study of matter. Atoms are the building blocks of matter. Neutrons and protons are located at the center of the atom. Protons are positively charged particles. Neutrons are particles that have no charge. Chapter 6 Chemistry in Biology 6.1 Atoms, Elements, and Compounds Electrons are negatively charged particles that are located outside the nucleus. Electron Arrangement • Electrons are organized in different energy levels or shells • The inner most level can hold 2 electrons • 2e, 8e, 8e, 18e, 18e, 32e, 32e • Valence Electrons: the electrons in the outermost level • These are responsible for atoms bonding together Chapter 6 Chemistry in Biology 6.1 Atoms, Elements, and Compounds Elements Element: is a pure substance that cannot be broken down into other substances by physical or chemical means. Each element has a unique name and symbol. Element Examples Chapter 6 Chemistry in Biology 6.1 Atoms, Elements, and Compounds The Periodic Table of Elements Horizontal rows are called periods. Tells the number of energy levels in each row Vertical columns are called groups or families. Tells the number of valence electrons in each family Chapter 6 Chemistry in Biology 6.1 Atoms, Elements, and Compounds Compounds: A pure substance formed when two or more elements combine Compounds are always formed from a specific combination of elements in a fixed ratio. Compounds cannot be broken down into simpler compounds or elements by physical means. Compound Examples • NaCl • 5 H2O • 7 CaCl2 Chapter 6 Chemistry in Biology 6.1 Atoms, Elements, and Compounds Isotopes Atoms of the same element that have the same number of protons and electrons but have a different number of neutrons • Elements are held together in compounds by bonds. • There are 2 main types of bonds: • Covalent • Ionic Chapter 6 Chemistry in Biology 6.1 Atoms, Elements, and Compounds Chemical Bonds Covalent bonds Chemical bond that forms when electrons are shared Occurs between nonmetals Chapter 6 Chemistry in Biology 6.1 Atoms, Elements, and Compounds Ionic Bonds Electrical attraction between two oppositely charged atoms (ions) or groups of atoms Chapter 6 Chemistry in Biology • Atoms are donated or gained • Occurs between metals and non-metals Chapter 6 Chemistry in Biology 6.1 Atoms, Elements, and Compounds The elements identified as metals tend to donate electrons. The elements identified as nonmetals tend to accept electrons. • Atomic number = number of protons • Atomic Mass = average mass of all the isotopes of an element – You can round this to find the mass number for the most common isotope of the element • Mass number = protons + neutrons 6.2 Chemical Reactions • 2 H + O → H2O • Which side contains the reactant(s)? • The product(s)? • What makes this reaction occur? Chapter 6 Chemistry in Biology 6.2 Chemical Reactions Energy of Reactions Activation energy is the minimum amount of energy needed for reactants to form products in a chemical reaction. Chapter 6 Chemistry in Biology 6.2 Chemical Reactions This reaction is exothermic and released heat energy. The energy of the product is lower than the energy of the reactants. Chapter 6 Chemistry in Biology 6.2 Chemical Reactions This reaction is endothermic and absorbed heat energy. The energy of the products is higher than the energy of the reactants. • We will learn about biological catalysts in the near future! 6.4 The Building Blocks of Life • All living things are compose of organic molecules • The six most common elements found in organic molecules include: C, H, N, O, P, S. Chapter 6 Chemistry in Biology 6.4 The Building Blocks of Life Organic Chemistry The element carbon is a component of almost all biological molecules. Chapter 6 Chemistry in Biology 6.4 The Building Blocks of Life Macromolecules Carbon atoms can be joined to form carbon molecules. Macromolecules are large molecules formed by joining smaller organic molecules together. Monomers: small, repeating organic molecules that usually form larger molecules They are also called biological polymers • There are four major macromolecules associated with biology: • Carbohydrates • Lipids • Proteins • Nucleic acids Chapter 6 Chemistry in Biology Chapter 6 Chemistry in Biology 6.4 The Building Blocks of Life Carbohydrates Compounds composed of carbon, hydrogen, and oxygen in a ratio of 1C: 2H: 1O General formula: (CH2O)n Chapter 6 Chemistry in Biology 6.4 The Building Blocks of Life If n is between three and seven the compound is called a simple sugar or monosaccharide. Ex. C6H12O6 Glucose is one very important monosaccharide used by cells for energy • It is found in the human bloodstream Two monosaccharides joined together form a disaccharide. Sucrose and lactose are two examples of disaccharides. Sucrose is table sugar Lactose is milk sugar How are disaccharides formed? • Dehydration synthesis: formation of disaccharide by removing water from the monosaccharides Longer carbohydrate molecules are called polysaccharides. Glycogen is an example of a polysaccharide. Animals store it in the liver It is a short term energy storage molecule How do organisms get energy from these????? • The bonds between them are broken, releasing energy • Hydrolysis: adding water to split a disaccharide or polysaccharide and release energy Functions of Carbohydrates: • Primary source of energy for organisms • Structural support in plants (cellulose) • Main component in shells (chitin) Carbohydrates Are: • Manufactured by green plants only: • Occurs during photosynthesis • 6 CO2 + 6 H2O → C6H12O6 + 6 O2 Chapter 6 Chemistry in Biology 6.4 The Building Blocks of Life Lipids Molecules made mostly of carbon and hydrogen Make Up: Fats Oils Waxes Functions of Lipids Primary function is to store energy Make up cell structures Form chemical messages between cells Protection (wax on plant leaves) Lipid Structure: • Fatty acid tail • Fatty acid tail is a chain of carbon atoms bonded to hydrogen atoms and other carbon atoms by single or double bonds • The bonds determine if the lipid is classified as saturated, unsaturated or polyunsaturated Basic Structure of Lipids Chapter 6 Chemistry in Biology 6.4 The Building Blocks of Life Saturated fats have tail chains with only single bonds between the carbon atoms. Unsaturated fats: lipids that have at least one double bond between carbon atoms in the tail chain Fats with more than one double bond in the tail are called polyunsaturated fats. Important Biological Lipids: • Phospholipids: create the structure and function of the cell membrane • Hydrophilic head: dissolves in water • Hydrophobic tail: does not dissolve in water • Why is this important? Lipids • Also, responsible for the formation of important steroids including hormones and cholesterol Chapter 6 Chemistry in Biology 6.4 The Building Blocks of Life Protein A compound made of small carbon compounds called amino acids Amino acids are small compounds that are made of carbon, nitrogen, oxygen, hydrogen, and sometimes sulfur. Chapter 6 Chemistry in Biology 6.4 The Building Blocks of Life Amino acids have a central carbon atom. One of the four carbon bonds is with hydrogen. The other three bonds are with an amino group (–NH2), a carboxyl group (–COOH), and a variable group (–R). Chapter 6 Chemistry in Biology • Amino acids are bonded together in a chain by peptide bonds • Proteins are also called polypeptides Protein Functions: • Make up mass • Involved in almost all functions – Structure – Chemical signals between cells – Control cell growth and repair – Enzymes (biological catalysts) Enzymes • Enzymes: biological catalysts • Made of proteins Chapter 6 Chemistry in Biology 6.2 Chemical Reactions Enzymes Catalyst is a substance that lowers the activation energy needed to start a chemical reaction. Activation energy: the minimum amount of energy needed for reactants to form products in a chemical reaction. • It does not increase how much product is made. • It does not get used up in the reaction. • How do enzymes work? Chapter 6 Chemistry in Biology 6.2 Chemical Reactions Substrates: Reactants that bind to the enzyme Active site: Specific location where a substrate binds on an enzyme Chapter 6 Chemistry in Biology 6.2 Chemical Reactions The active site changes shape and forms the enzyme-substrate complex, which helps chemical bonds in the reactants to be broken and new bonds to form. Factors such as pH, temperature, and other substances affect enzyme activity. Chapter 6 Chemistry in Biology • Nucleic Acids: • Made up of smaller subunits called nucleotides • Nucleotides consist of carbon, nitrogen, oxygen, phosphorus, and hydrogen atoms Nucleic Acid Functions: • Store and transmit genetic information • Two types of nucleic acids: – DNA – RNA