Read the summary and the most important questions on AP biology 2

• chapter 5

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• Which of the following types of molecules are the major structural components of the cell membrane?

  phospholipids and proteins

• When biological membranes are frozen and then fractured, they tend to break along the middle of the bilayer.  The best explanation for this is that

  the hydrophobic interactions that hold the membrane together are weakest at this point.

• The presence of cholesterol in the plasma membranes of some animals

  enables the membrane to stay fluid more easily when cell temperature drops

• According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids?

  they can move laterally along the plane of the membrane.

• Which of the following is one of the ways that the membranes of winter wheat are able to remain fluid when it is extremely cold?

  by increasing the percentage of unsaturated phospholipids in the membrane

• In order for a protein to be an integral membrane protein it would have to be

  amphipatic, with at least one hydrophobic region

• When a membrane is freeze-fractured, the bilayer splits down the middle between the two layers of phospholipids.  In an electron micrograph of a freeze-fractured membrane, the bumps seen on the fractured surface of the membrane are

  integral proteins

• Which of the following is a reasonable explanation for why unsaturated fatty acids help keep any membrane more fluid at lower temperatures?

  The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.

• Which of the following is true of integral membrane proteins?

  they are usually transmembrane proteins

• The primary function of polysaccharides attached to the glycoproteins and glycolipids of animal cell membranes is

  to mediate cell-to-cell recognition