CH 2 Chemical Components of Cells

CH 2 Chemical Components of Cells - 9/2/09 Chapter 2...

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9/2/09 1 Chapter 2 Chemical Components of Cells Why is biological chemistry important? Understanding the structure and properties of major classes of biological molecules is essential to understanding cellular function at any level.
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9/2/09 2 • Understand how covalent bonds form molecules from atoms • Understand the nature and importance of noncovalent bonds • Understand the chemical basis of the unique, life‐ dependent proper:es of water • Understand the key role of carbon in forming biological molecules • Know and understand importance of four classes of biological molecules – Carbohydrates – Lipids – Proteins – Nucleic Acids
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9/2/09 3 The number of protons in an atom determines its atomic number, and its number of electrons
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9/2/09 4 Types of Chemical Bonds • Strong – Covalent bonds – Ionic bonds • Weak – Hydrogen Bonds – Hydrophobic Interactions – Van der Waals Attractions Figure 2-6 Essential Cell Biology (© Garland Science 2010) Strong Bonds
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9/2/09 5 The strength of ionic but not covalent bonds is greatly affected by water Table 2-1 Why? Water has polar covalent bonds Nonpolar covalent bonds Asymmetric charge distribution
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9/2/09 6 The electrical charge effects of water can partially shield charges between ions Hydrogen bonds Electrostatic interaction between a H held in a polar covalent bond and another atom (usually O or N) also held in polar covalent bond. See Panel 2-2 and 2-7
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9/2/09 7 • Water bond angle and polar covalent bonds produces dipolar molecule • Many proper:es of water depend on ability of water molecules to form hydrogen bonds with other (polar or ionic) molecules • Unique proper:es of H 2 O – High boiling point – High speciFc heat – Liquid at RT – Lower density as solid (ice floats) – Surface tension, etc. Figure 2.4 Other types of hydrogen bonds
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9/2/09 8 Hydrogen Bond to Polar Substances Diferent covalent bond geometries
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9/2/09 9 Hydrophobic Interactions “Water fearing” attraction between nonpolar molecules caused by repulsion from water. Where in a cell might this type of interaction be needed? See Panels 2-2 and 2-7 Figure 2.5 Hydrophobic interac&ons
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9/2/09 10 van der Waals Attractions • Weak interaction caused by transient electrical charges, dependent on the distance between atoms • In large numbers can be significant in the attraction between macromolecular surfaces See Panel 2-7 Ionization of Water Acids, Bases and Buffers Panel 2-2
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9/2/09 11 Quantities of atoms and molecules • Atoms and molecules are very small so a scale factor is generally used to describe quantities - Mole • One Mole is 6 x 10 23 individuals (Avogadro’s number) • The mass of 1 mole of a substance is determined from its atomic or molecular weight
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This note was uploaded on 04/09/2010 for the course BIOL 213 taught by Professor Mcknight during the Spring '07 term at Texas A&M.

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CH 2 Chemical Components of Cells - 9/2/09 Chapter 2...

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