MIDTERM 2

MIDTERM 2 - Answers to Study Guide for Midterm 2/ BIBC 100...

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Answers to Study Guide for Midterm 2/ BIBC 100 / Structural Biochemistry 9. Transfer RNA contains a fair amount of unusual bases (~25%). During the synthesis of a tRNA molecule, however, only ATP, GTP, UTP and CTP are used, but are posttranscriptionally modified by enzymes. Imagine a cell that is defective in an enzyme that methylates guanine bases in tRNA's. What would the effect be on tRNA-mRNA interaction? this affects codon-anticodon recognition and wobble mechanism; example: phenylalanyl-tRNA has a methylated G at the first anticodon position allowing for a wobble (loose) interaction with the third codon base on the mRNA 10. Define the chemical bonds between units in the three major biochemical macromolecules: proteins peptide bonds , nucleic acids phosphodiester bonds polysaccharides glycosidic bonds . Write down the generic reaction equation for each type (substrate product) and name enzymes involved in the catalysis for both the forth and back reactions. all are condensation reactions releasing a molecule of water in the process; reversal will break the bond; this reaction is known as hydrolysis using up one molecule of water (cosubstrate); peptide bond and phosphodiester bond formation require large, multicomponent complexes; hydrolysis is usually done by small, single proteins calles proteases (peptide bonds), nucleases (phosphodiester bond), and glycosidase 11. What effect drives the formation of phospholipid bilayers? hydrophobic effect Define the interior of the membrane by its dielectric property. dielectric constant 2 in membrane What does 'amphipathic' mean, and how does this property relate to the stability of membranes? amphipathic molecules contain both polar and non-polar parts, phospholipids are amphipathic and form bilayers by associating their headgroups together forming polar surfaces and putting their fatty acid tails together forming a hydrophobic core What can happen to amphipathic peptides in aqueous solution? amphipathic peptides can form helical bundles in solution with a hydrophobic core and polar surface making the bundle wate soluble 12. Cellulose Fibers are composed of many polysaccharide strands of several thousand glucose molecules. Monomeric glucose is water soluble, yet cellulose fibers do not dissociate from the supramolecular bundle into single strands. . Why?
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This note was uploaded on 04/23/2008 for the course BIBC 100 taught by Professor Nehring during the Spring '07 term at UCSD.

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MIDTERM 2 - Answers to Study Guide for Midterm 2/ BIBC 100...

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