Chemistry 153A, Spring 2009, Lecture 1 Midterm 1, Exam A – Answer Key 2.True or False? a.False. Water is only polar. b.False. The stronger an acid, the lowerits pKa. c.True d.False. Bonds to α-carbons each sit in a peptide plane, and there is rotation about these bonds. e.True f.True g.False. Backbone carbonyl groups point toward an α-helix’s carboxyl-terminal end. h.True i.False. The 3.3 helix of collage is left-handed. j.False. Peptidoglycanprovides stability to the bacterial cell wall. 3.e; explanation:a.is false, because a reducing sugar becomes oxidizedin the presence of Cu2+. b.is false, because some reducing sugars (ex: glyceraldehyde) cannot form a ring. c.is false; a polysaccharide can have reducing and non-reducing ends, but the molecule as a whole will be either reducing (if it has a reducing end) or non-reducing (if all ends are non-reducing). d.is false; the monosaccharide on the right has its anomeric carbon in the hemi-acetal form, so it is reducing.
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polar. b. False, True d. False, True g. False, True i. False, Lys B. Cys C. Arg