Section 28: Carbohydrates: Functions of Carbohydrates Part A Polymers that contain sugars . .. (a) may store hereditary information. (b) may store energy. (c) may protect cells. Both (b) and (c). (a), (b), and (c). Correct Good choice! Polymers that contain sugars do all the named functions and more. For example, they also lubricate the path of roots through soil and they glue plant cells together. Section 32: Lipids: Functions of Lipids Part A What do fats, steroids, and waxes have in common? (a) Moderate polarity. (b) Low solubility in water. (c) They occur in membranes. Both (a) and (c). Both (b) and (c). Correct Correct! Low water solubility is the trait that defines lipids. Part B Dr. Haxton told one of his students, "To move in the bloodstream, fats need the help of phospholipids." What would a good student say? Yes. Nonpolar molecules aren't compatible with water. Not so. Fats are small enough to travel easily without help. Right. Fats are too polar to travel alone in water. You have it backwards. Fats help phospholipids to travel. Sorry, Dr. Haxton! Help comes from cholesterol, not phospholipids. Correct Good choice! Water rejects nonpolar molecules such as fats, so fats travel inside particles that are coated with polar parts of phospholipids and proteins. Section 36: Proteins: Functions of Proteins
Part A Which biological activity does NOT directly involve proteins? Sensing light. Defending cells against viruses. Changing the shape of a cell. Breaking food polymers into smaller molecules. None of the above; proteins are involved in all of them. Correct Right! Proteins have all the listed functions and many more. Section 40: Proteins: Secondary Structure Part A The helical foldings of proteins are stabilized mainly by bonds between . .. water molecules. ionic groups. S and S. CO and NH. side chains. Correct Right! Hydrogen bonds between these groups keep the helix coiled. Part B Which of the following is true of pleated sheet foldings within a polypeptide? The side chains are parallel to the plane of the sheet.
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