55. Why does it make some sense that tropical oils and mammal fats should contain a higher prevalence of saturated fatty acids compared to cold-climate plants or cold-blooded animals? What is a phospholipid, and how is its structure related to but distinct from that of a triacylglycerol? What is a sphingolipid, and how is its structure related to that of a phospholipid? Phospholipids are described as being amphipathic. At the biochemical level, what is meant by this term and how does this property relate to the role of phospholipids in cellular membranes? Why is the collection of lipids in the plasma membrane more accurately referred to as a macromolecular aggregate than a macromolecule (like carbs, proteins and nucleic acids)? 56. 57. 58. 59. 60. What is cholesterol, and how does it affect the physical properties of the cellular membranes that it is a part of? 61. Is cholesterol a component of all the plasma membrane in all organisms? Explain your answer. 62. How does cholesterol relate to the general class of nonpolar molecules known as steroids? 63. What chemical groups are attached to the alpha carbon in a typical amino acid? Which of these is/are consistent across all kinds of amino acids, and which is/are variable? 64. What determines if an amino acid is classified as “polar,” “nonpolar,” “charged-acidic,” or “charged-basic”? 65. What is “special about the three amino acids we highlighted (glycine, proline and cysteine)? 66. What is the “NCC backbone” of a polypeptide, and what is meant by an “amino” and a “carboxyl terminus of a protein? 67. What is the primary structure of a polypeptide and in what sense does it “dictate” higher levels of protein structure 68. Explain the observation that a mutation that changes one amino acid in a protein could have A) no effect on the 69. 70. 71. protein’s structure/function, B) a moderate effect or C) ablate function altogether. What factors might allow you to predict the potential consequence of any such change? What are the principal motifs in the secondary structure of proteins, and what type(s) of chemical interactions stabilize these structural motifs? What are some examples of functional properties of proteins that can be associated with alpha-helices and beta pleated sheets? What type(s) of chemical interactions stabilize a polypeptide’s tertiary structure? Which of these forces are “strong”