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Area IA - Molecules and Cells: Chemistry of Life (7%)


Chapter 2: Basic Chemistry (Main ideas from Biology, 9th Edition, by Sylvia S. Mader)

2.1 Chemical Elements
  • All living and nonliving things are matter composed of elements. Six elements (CHNOPS) in particular are basic to life. (Page 20)
  • Atoms have an atomic symbol, an atomic number, and an atomic mass. The subatomic particles (protons, neutrons, and electrons) determine the characteristics of atoms. (Page 21)
  • Isotopes of an element have the same atomic number but differ in mass due to a different number of neutrons. Radioactive isotopes, which emit radiation, have the potential to do harm but also have many beneficial uses. (Page 23)
  • The number of electrons in the outer shell determines whether an atom reacts with other atoms. (Page 23)
2.2 Elements and Compounds
  • The transfer of electron(s) between atoms results in ions that are held together by an ionic bond, the attraction of negative and positive charges. (Page 24)
  • In a covalent molecule, atoms share electrons; the final shape of the molecule often determines the role it plays in cells and organisms. (Page 25)
  • The water molecule is a polar molecule and has an asymmetrical distribution of charge: one end of the molecule (the oxygen atom) carries a slightly negative charge, and the other ends of the molecule (the hydrogen atoms) carry slightly positive charges. (Page 26)
  • A hydrogen bond occurs between a slightly positive hydrogen atom of one molecule and a slightly negative atom of another molecule, or between atoms of the same molecule. (Page 26)
2.3 Chemistry of Water
  • Water has unique properties that allow cellular activities to occur and that make life on Earth possible. (Page 29)
  • A pH value is the hydrogen ion concentration [H+] of a solution. Buffers act to keep the pH within normal limits. (Page 31)
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Chapter 3: The Chemistry of Organic Molecules (Main ideas from Biology, 9th Edition, by Sylvia S. Mader)

3.1 Organic Molecules
  • Organic molecules are diverse and complex. Carbon skeletons vary in size and shape; functional groups have various chemical characteristics, and isomers occur. (Page 37)
  • Organic molecules are routinely built up in cells by the removal of water (H2O) during a dehydration reaction. They are degraded in cells by the addition of water during a hydrolysis reaction. (Page 38)
3.2 Carbohydrates
  • Polysaccharides such as starch and glycogen are polymers of glucose. Plant cells use starch, and animal cells use glycogen for short-term energy storage. (Page 40)
  • Plant cell walls contain cellulose. The shells of crabs and related animals, and cell walls of fungi, contain chitin. (Page 41)
3.3 Lipids
  • Fats and oils are triglycerides (one glycerol plus three fatty acids). They are used as long-term energy storage compounds in plants and animals. (Page 42)
  • Phospholipids have polar heads and nonpolar tails; therefore, they are suited to forming a membrane that surrounds the cell. (Page 44)
  • Steroids are a type of lipid because of their insolubility in water. Steroids are derived from cholesterol, a component of the plasma membrane. The sex hormones are steroids. (Page 44)
  • Waxes contain fatty acids attached to long-chain alcohols. Waxes have many different types of functions, primarily in plants but also in animals. (Page 45)
3.4 Proteins
  • The sequence of amino acids in a polypeptide determines its final shape because it determines with R groups interact. The function of a protein is dependent on its shape. (Page 49)
3.5 Nucleic Acids
  • The nucleic acids DNA and RNA are polymers of nucleotides. DNA is the genetic material, and RNA is an intermediary during the process of protein synthesis. (Page 51)
  • ATP is a common high-energy molecule in cells. ATP breaks down to ADP + P, releasing energy, which is used for all the metabolic work done in a cell or organism. (Page 52)

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Chapter 6: Metabolism: Energy and Enzymes (Main ideas from Biology, 9th Edition, by Sylvia S. Mader)

6.1 Cells and the Flow of Energy
  • The first law of thermodynamics—the law of conservation of energy—states energy cannot be created or destroyed, but it can be changed from one form to another. (Page 102)
  • The second law of thermodynamics states energy cannot be changed from one form to another without a loss of usable energy. (Page 103)
  • Energy exists in several forms. When energy transformations occur, energy is neither created nor destroyed. However, there is always a loss of usable energy. For this reason, living things are dependent on an outside source of energy that ultimately comes from the sun. (Page 103)
6.2 Metabolic Reactions and Energy Transformations
  • ATP is a carrier of energy in cells. It is the common energy currency because it supplies energy for many different types of reactions. (Page 105)
6.3 Metabolic Pathways and Enzymes
  • Enzymes are protein molecules that speed chemical reactions by lowering the energy of activation. They do this by forming an enzyme-substrate complex. (Page 107)
  • Enzymes speed reactions by forming a complex with their substrates. Various factors affect enzyme speed, including substrate and enzyme concentrations, the temperature and pH of the medium, and the presence or absence of cofactors and inhibitors. (Page 109)

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Chapter 6 Animations
Click the links to see the animations full size.
How Enzymes Work

Enzyme Action and the Hydrolysis of Sucrose

A Biochemical Pathway

Feedback Inhibition of Biochemical Pathways

Proton Pump