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Chapter 2 The Chemical Composition of Cells Learning Objectives- 1 Understand the Structure of the Molecular Components of Living Organisms Carbohydrates, which supply and store energy and serve as structural building blocks, include sugars and polymers of sugars. Proteins, which catalyze reactions and are structural building blocks, are polymers of amino acids. The nucleic acids DNA and RNA, which code and express genetic information, are polymers of nucleotides. Lipids are membrane components consisting mainly of carbon and hydrogen atoms derived from acetates and other molecules. Secondary metabolites such as phenolics, alkaloids, and terpenoids often protect or strengthen plants. Learning Objectives -2 To Understand Energy and Chemical Reactions Energy can be stored and can move or change matter . Chemical reactions involve either a net input or a net output of free energy. The movement of electrons is the basis of energy transfer through oxidation and reduction reactions. The terminal phosphate bond in ATP releases energy when broken. NADH, NADPH, and FADH2 are universal carriers of energy-rich electrons in living organisms. Learning Objectives -3 To Understand the Nature of Chemical Reactions and Enzymes Enzymes position reactants, allowing reactions to occur with minimal activation energy or increase in temperature. Cofactors such as coenzymes interact with enzymes to assist reactions and indirectly provide energy in the form of electrons for biochemical reactions. Competitive and noncompetitive inhibition can slow or stop enzymatic reactions and pathways. Enzymatic reactions are linked together into metabolic pathways. Learning Objective Know the basic structure of atom, and know the role of ionic, covalent and hydrogen bonds. Key Terms: Atoms Proton Neutron positive electric charge, small mass uncharged, about same mass as proton Electron negative charge, extremely small mass A Carbon Atom Electrons Move around the nucleus at different energy levels Allow elements to combine chemically to form chemical compounds Ions are atoms which tend to gain or lose electrons Electron Configurations Acids and Bases Acids dissociate in water to form hydrogen ions (protons, H+) Bases dissociate in water to yield negatively charged hydroxide ions (OH-) pH Scale A measure of the relative concentrations of H+ and OH- in a solution A solution’s acidity or alkalinity is expressed in terms of the pH scale KEY TERMS IONIC BOND An electrostatic attraction between oppositely charged ions Ionic Bonding KEY TERMS COVALENT BOND A chemical bond involving one or more shared pairs of electrons Covalent Bonding in Hydrogen Covalent Bonding in Methane KEY TERMS HYDROGEN BOND An attraction between a slightly positive hydrogen atom in one molecule and a slightly negative atom (usually oxygen) in another molecule Animation: How Atoms Bond CLICK TO PLAY LEARNING OBJECTIVE Discuss the properties of water, and explain the importance of water to life Water Has a strong dissolving ability Molecules form hydrogen bonds with one another (cohesion) Molecules form hydrogen bonds to substances with ionic or polar regions (adhesion) Adhesion & Cohesion are particularly important for transport All living things require water to survive Almost all chemical reactions that sustain life occur in aqueous solution High Melting & Freezing Points Insulation Property after freezing (e.g., lakes) Water Structure Animation: Structure of Water CLICK TO PLAY LEARNING OBJECTIVE Describe the chemical compositions and functions of carbohydrates, lipids, proteins, and nucleic acids KEY TERMS CARBOHYDRATE An organic compound containing carbon, hydrogen, and oxygen in the approximate ratio of 1C:2H:1O Carbohydrates 1 Include sugars, starches, cellulose Important fuel molecules, components of molecules (nucleic acids) and cell walls Carbohydrates 2 Monosaccharides Disaccharides simple sugars two monosaccharide units Polysaccharides many monosaccharide units Common Monosaccharides Sucrose Synthesis Starch: A Storage Polysaccharide Cellulose: A Structural Polysaccharide KEY TERMS LIPID Any of a group of organic compounds that are insoluble in water but soluble in fat solvents Lipids 1 Have a greasy consistency, do not readily dissolve in water Important fuel molecules, components of cell membranes, waterproof coverings over plant surfaces, light-gathering molecules for photosynthesis Lipids 2 A neutral fat or oil molecule is composed of a molecule of glycerol plus one, two or three fatty acids Formation of a Neutral Fat or Oil KEY TERMS PROTEIN A large, complex organic compound composed of amino acid subunits Protein A macromolecule composed of amino acids joined by peptide bonds Order of amino acids determines structure and function of a protein molecule Enzymes: Proteins that increase the rate of chemical reactions Amino Acids Peptide Bonds Protein Synthesis Animation http://www.wisconline.com/objects/index_tj.asp?ob jid=AP1302 Organization of Protein Molecules KEY TERMS NUCLEIC ACID Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) Large, complex organic molecules composed of nucleotides Nucleic Acids Control the cell’s life processes Deoxyribonucleic acid (DNA) Transmits information from one generation to the next Ribonucleic acid (RNA) Involved in protein synthesis Nucleotides Repeating units that form nucleic acids Order of nucleotides in a nucleic acid chain determines the specific information encoded Adenosine triphosphate (ATP) A modified nucleotide compound important in energy transfers in biological systems Nucleic Acids Nucleic Acids Nucleic Acids DNA Replication Animation http://www.visionlearning.com/libra ry/module_viewer.php?mid=63&l= &c3= KEY TERMS ADENOSINE TRIPHOSPHATE (ATP) An organic compound of prime importance for energy transfers in biological systems ATP ATP is a nucleotide that performs many essential roles in the cell. It is the major energy currency of the cell, providing the energy for most of the energy-consuming activities of the cell. It is one of the monomers used in the synthesis of RNA and, after conversion to deoxyATP (dATP), DNA. It regulates many biochemical pathways. LEARNING OBJECTIVE Discuss the role of enzymes in cells KEY TERMS ENZYME An organic catalyst, produced within an organism, that accelerates specific chemical reactions ACTIVATION ENERGY The energy required to initiate a chemical reaction Enzymes Speed up a chemical reaction by lowering its activation energy (energy needed to initiate the reaction) Most enzymes are highly specific and catalyze only a single chemical reaction Without enzymes, chemical reactions in cells would occur too slowly to support life Enzymes and Activation Energy Enzyme-Substrate Complex Energy & Chemical Reactions Energy can be stored and can move or change matter: Potential energy is stored energy, while kinetic energy is energy having to do with motion. The first law of thermodynamics states energy can be harnessed and transformed but not created or destroyed. The second law of thermodynamics states that every transfer of energy increases the entropy (disorder) of matter in the universe. LEARNING OBJECTIVE State the first and second laws of thermodynamics, and describe how each applies to plants and other organisms KEY TERMS FIRST LAW OF THERMODYNAMICS Energy cannot be created or destroyed, although it can be transformed from one form to another SECOND LAW OF THERMODYNAMICS When energy is converted from one form to another, some of it is degraded into a lowerquality, less useful form Energy The ability to do work Plants and other organisms cannot create the energy they require to live, but must capture energy from the environment and use it to do biological work Potential and Kinetic Energy Entropy Continuously increases in the universe as usable energy is converted to lower-quality, less usable form (heat) As each energy transformation occurs in organisms, some energy changes to heat Given off into the surroundings Can never be used again for biological work Animation: Activation Energy Click To Start Secondary Metabolites Secondary metabolites such as phenolics, alkaloids, and terpenoids often protect or strengthen plants