Bio notes section 2

Bio notes section 2 - Biology Notes Section 2: Lecture 3/...

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Biology Notes Section 2: Lecture 3/ Chapter 2 Molecules of Life General: - Earth’s organisms are nearly 50% carbon when water is filtered out; 18% carbon including water. - Organic chemistry: branch devoted to study of molecules with carbon as their central element. - Molecules are built on carbon skeletons : - Carbon always has 4 covalent bonds because it has 4 valence electrons (needs 8); all carbon compounds are built on this principle. - Carbon can make chains, branching structures, rings, and double (covalent) bonds. - Examples of simple (exclusively) hydrocarbon skeletons: [hydrophobic] o Chain 2 carbon, each linked to 3 hydrogen = ethane. 3 carbon, the outer 2 linked to 3 H each and the middle carbon linked to 2 H (i.e. 8 H) = propane. o Branching isobutane (an isomer of butane- isomers are molecules with the same chemical formulas but different spatial arrangements of atoms). o Double bonds butene o Rings benzene Functional groups: groups of atoms that confer a special property on a carbon-based molecule; adding a functional group to a hydrocarbon molecule (only H and C) adds certain new qualities. 1. Hydroxyl groups (--OH) the addition of –OH group to a hydrocarbon creates some form of alcohol. For example, a hydroxyl group added to ethane hydrocarbon (a gas) makes liquid ethyl alcohol. a. Hydroxyls are POLAR, very water-soluble, and found in carbohydrates + alcohols. b. Molecules w. hydroxyl groups therefore allow hydrogen bonding. 2. Carboxyl groups (--COOH) carboxyl is an organic acid consisting of a carbon double- bonded to an oxygen and single-bonded to a hydroxyl group. a. Properties: highly POLAR, releases hydrogen in solution (hence is an acid). b. Example: acetic acid (vinegar). Carboxyls are found in fatty acids and amino acids. 3. Phosphates (--PO4) phosphate groups have highly energetic bonds; breaking off a phosphate thus releases a lot of energy. a. Properties: POLAR, contribute water solubility. b. Found in DNA and ATP (adenosine triphosphate = major energy currency of a cell). 4. Aminos (--NH2) properties: POLAR (due to high electronegativity of nitrogen); can dissolve in water. a. Amino groups are basic: they can bind H+ in water solutions. Example: ammonia.
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Monomers, dimers, and polymers - Subunits of larger molecules/ compounds. - 2 monomers = 1 dimer (monomers are the same = homodimer; different = heterodimer). - 3 monomers = 1 polymer (all monomers identical = homopolymer; 2 or more different = heteropolymer). 4 monomers (or combo of polymers/monomers etc.) = 1 tetramer. -
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This note was uploaded on 12/18/2011 for the course BIOL 115 taught by Professor Brown during the Fall '08 term at McGill.

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Bio notes section 2 - Biology Notes Section 2: Lecture 3/...

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