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Cards In This Set
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What makes water a universal solvent?
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1. polarity
2. H bonding with other polar molecules 3. electronegativity WONT dissolve nonpolar molecules |
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How much water makes up a typical eukaryotic cell? how much water is in the human body?
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Eukaryotic cell: 65-70%
Human Body: 65% |
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What chemical properties contributes to water's ability to dissolve molecules?
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1. Polarity
2. Hydrogen bonding 3. reversible ionization |
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What are covalent bonds?
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1. stable
2. 50-200kcal/mol energy released when formed 3. shared arrangement of electrons -covalence is a NONPOLAR interaction |
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Importance of Polarity
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- leads to noncovalent interactions
- partial dipoles confer reactivity - explains why molecules are hydrophilic and hydrophobic; importance of water as an organizing principle -determines whether a molecule is or isn't soluble in water |
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The order from most electronegative atoms to least electronegative atoms are..
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O>N>S>C>P>H
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Hydrogen bonding
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* a non-covalent interaction
- contributes to structure and flexibility of macromolecules (i.e water) - average H-bong between water molecules lasts 10 picoseconds -weak association (1-5kcal/mole) between an electronegative atom (acceptor) and an H atom that is covalently bonded to another atom (donor) *stability is determined by arrangement in space -linear = strong -angled = weak |
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What is the Hydrophobic effect
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* Another noncovalent interaction
* when a molecule can't form hydrogen bonds with water, so it avoids water molecules all together -creates attraction between other non polar molecules * an entropy driven reaction * hydrophobic interactions form spontaneously -nonpolar substances in water are stabilized by them * CELL MEMBRANES FORM because of hydrophobic effect |
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Why are nonpolar molecules insoluble in water?
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* they lead to a more ordered array of water molecules
-leads to a decrease in entropy of water, which is unfavorable |
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What is Entropy
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* a measure of disorder - high entropy is a disordered state
* also refers to possible arrangements of molecules *degradation of molecules is favored , "more entropic" *synthesis isn't favored unless energy is placed into system |
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Electrostatic, ionic interactions
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*Another noncovalent interaction
*occur between atoms with a complete positive and negative charge *strength of interaction is determined by DISTANCE and the SOLVENT *i.e protein-protein interactions, DNA- protein interactions (sugar-phosphate backbone), catalytic mechanism - no partial ionization |
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Van der Waals forces
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*Another noncovalent interaction
*charge fluctuations: transiently produces + or - poles even in a nonpolar molecule *occurs over very short distances, present with "snug fit" between atoms *weakest noncovalent interaction (.1-1kcal/mol) |
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Why are noncovalent interactions important
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*weak and transient: gives macromolecules FLEXIBILITY
* provide STABILITY to macromolecular structure-- large numbers are present in a molecule, unlikely that all will be broken at same time *essential to SPECIFICITY and catalytic efficiency of enzymes |
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Chemical and physical properties of cellular molecules
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*essentially carbon based
*types of bonds between atoms *strength of chemical bonds *arrangement in space-- 3D structure *influence of water on structure and interactions between biological molecules |
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How and why do structures form?
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*covalent and noncovalent interactions
*interact with or avoid water * thermodynamic considerations: most structures don't form spontaneously but require an input of energy, catalysts, or other stuctures. |
