Feedback for Multiple Choice Quiz 23

  1. Carbohydrates are found on the surfaces of membranes. Cholesterol and phospholipds span only half the thickness of the bilayer.
  2. Only the membrane-spanning, integral proteins function directly in active transport, e.g. by forming pores or channels.
  3. Nucleic acids are "associated with" or "attached to" membranes, but are not found "in membranes".
  4. By definition, active transport involves the movement of ions or molecules against a concentration gradient, i.e. in a specific direction relative to the membrane doing the transporting.
  5. This is really minutiae, but the list at the bottom of the the Lecture 23 notes looked like a natural multiple choice question! The important point is that a variety of lipids are used to anchor proteins in the membrane.
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