Lec_2_3 - Chapter 2. Cell Chemistry and Biosynthesis. What...

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Chapter 2. Cell Chemistry and Biosynthesis. What are cells made of, and how are these things made?
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Cells are made of relatively few types of atoms: C, O, N, and H are most common. P and S will also be frequently encountered. Rarer but essential elements include Cl, Ca, K, Na, Fe. (Includes water which constitutes 70% of the cells mass) Figure 2-3 Molecular Biology of the Cell (© Garland Science 2008)
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The outermost electrons determine how atoms interact. Conceptualize atom as a cluster of protons and neutrons in the center with electrons moving in shells (orbitals). Atoms react to fill their outer electron shell: 2, 8, 8, etc. A covalent bond forms when electrons are shared by two atoms. An ionic bond forms when an electron is transferred from one atom to another resulting in positively (cation) and negatively (anion) charged ions that can attract to each other. Atoms are bonded together into molecules by covalent bonds. Figure 2-5 Molecular Biology of the Cell (© Garland Science 2008)
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Covalent bonds are strong and serve to connect the atoms constituting individual molecules. Table 2-1 Molecular Biology of the Cell (© Garland Science 2008)
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The spatial orientation and type of bonds formed between atoms contribute to the shape of macromolecules. Figure 2-8 Molecular Biology of the Cell (© Garland Science 2008)
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Polar bonds form between atoms of dissimilar electronegativity. Nonpolar bonds form between atoms of similar electronegativity. Electronegativity measures the attraction an atom has for electrons. Atoms bonded by polar bonds acquire partial “+” or “-” charge. Polar: O-H; N-H Nonpolar: C-C; C-H Figure 2-10 Molecular Biology of the Cell (© Garland Science 2008)
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Some polar molecules form acids and bases in water. Acids lower the pH by releasing H + ; Bases raise the pH by associating with H + . CH 3 - N H H + O H H CH 3 - N H H + O H H + - Hydroxide ion δ - δ + δ + recall pH = -log[H+]; [H + ] = 10 -7 M for pure water and for the cytoplasm. Figure 2-13a Molecular Biology of the Cell (© Garland Science 2008)
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Covalent ensembles of atoms commonly occurring in molecules of cells. (ie. chemical or functional groups) CH 3 methyl OH hydroxyl COO - carboxylate CO carbonyl NH 3 + amine SH sulfhydryl PO 3 = phosphate
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4 types of non-covalent interactions help bring molecules together in cells. Electrostatic attraction - (
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This note was uploaded on 09/16/2008 for the course MICRB 251 taught by Professor Gilmour,davidscoreese,josephc.tien,ming during the Fall '08 term at Pennsylvania State University, University Park.

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Lec_2_3 - Chapter 2. Cell Chemistry and Biosynthesis. What...

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