1.A double bond. - acid typically has an even number of carbons, 1...

Chapter 2 1.A double bond.

2.There are two fatty acids attached to the glycerol backbone via ester linkages. Each fatty acid typically has an even number of carbons, 14-24 of them. One of the fatty acids will be saturated, the one on carbon #2 is unsaturated.The remaining glycerol carbon is linked to a phosphate group, which may or may not have an R group attached. It is the identity of the R group that is used for most naming purposes (e.g.phosphatidylcholine, phosphatidylethanolamine).

3.Phospholipids. Within this class, phosphatidylcholine is most common.

4.The first choice is incorrect because there is no unsaturated fatty acid.The second choice is incorrect because there is an unsaturated fatty acid on the terminal carbon of glycerol.  In addition, there is a saturated fatty acid attached to the second glycerol carbon.The third choice is correct.

5.The described phospholipid is phosphatidylcholine. PC can be found on either side of the plasma membrane, but it is more commonly found on the outside layer.

6.The charge is important because it allows cells such as macrophages to recognize apoptotic cells. Phospholipid locations in the cell membrane are scrambled during apoptosis, which will translocate some phosphatidylserines to the extracellular face.

7.Yes, most phospholipids are able to move about the plasma membrane. Movement is like people moving about in a crowded mall.

8.Cholesterol adds both fluidity and stability to the plasmid membrane.

9.Flippases are specific in their action, translocating phosphatidylserines to the cytoplasmic face of the membrane. Scramblases randomly move phospholipids from one face to the other, which disturbs the ordered structure of the plasma membrane. Flippases are involved with organizing newly formed plasma membranes, scramblases are active during apoptosis.

10.a.V= RT zℑ ln( C o C i) Since the concentration outside the cell is given as concentration in the blood, T is assumed to be 37 °C = 310.0 K.Na +

: 0.067 V = +67 mV

(Biotechnology and its Applications, Using Cells to Change the World, 2e W.T. Godbey) (Solution Manual, There is no Solution Manual for Chapter 1) 1 / 4

K +

: -0.095 V = -95 mV

Cl -

: -0.090 V = -90 mV

b.Being more concentrated inside the cell, ln(Co/Ci) will be negative. The only way to resolve the positive membrane potential using the Nernst equation is if the ions carry a negative charge.c.Being more concentrated outside the cell, ln(Co/Ci) will be positive. The only way to resolve the negative membrane potential using the Nernst equation is if the ions carry a negative charge.

11.a.Histidine. Its pKa is the one closest to 7.4.b.His, Asp, Glu. Because lysosomal pH is so much lower than that of the early endosome, amino acids with lower pKas can be added to the list. This happens to be the amino acids that ionize negative.

12.A lipid. It is hydrophobic.

13.Yes. Transporters are proteins, and they adhere to the same folding rules as other proteins.

14.Not necessarily. It depends on the concentrations of the given ions outside versus inside the cell.

15.The overall membrane potential for a given ion, which relates the chemical gradient to the electrical gradient for that ion.

16.156.5 mM

17.No. They are physically too large.

18.Yes.

19.ABC transporters are active transporters that are used to transport hydrophobic molecules such as lipids, steroids, and toxins across the cell membrane. “ABC” stands for “ATP- binding cassette”. 2 / 4

20.One ATP is hydrolyzed to provide the energy to transport 3 NA + out of the cell and 2K + into the cell.

21.It is too small to allow larger ions to pass. The charges of amino acids within the channel are precisely spaced to interact with potassium ions as they pass through. For smaller ions, these amino acids are spaced too far from one another to facilitate their movement through the channel.

22.Channels are always open. Transporters have specific binding sites that must be filled to induce a conformation change that will open a pathway for the molecule to get into the cell.

23.No! LDL is not cholesterol, it is a lipoprotein.

24.Clathrin coated pits would not be able to pinch off from the plasma membrane after forming without leakage of cellular or vesicular contents.

25.The statement is incorrect. If a lysosome ruptures, the relatively higher pH of the cytoplasm will cause the released degradative enzymes to fold into inactive conformations.

26.Pumping HCO3 - into the lysosomal interior would cause the pH to rise as protons were absorbed, thereby causing the degradative enzymes (acid hydrolases) to fold incorrectly and lose activity. No, the lysosome would not function correctly.

27.Having different Fc and Fv regions a two-fold effect in IgG antibodies. Varying Fv regions allows for a multitude of antigens to be recognized by this class of immunoglobulin. Having consistent Fc regions allows for recognition of IgG-coated antigens by professional phagocytes.

28.a.Recognition of antibodies, recognition of apoptotic cells, recognition of complement, Recognition of oligosaccharides or glycoproteins.b.No. Pinocytosis occurs spontaneously.

29.With heroin and other opioid drugs, receptors are not recycled. With repeated exposure to the drug, fewer opioid receptors will be present on the cell surface, so fewer heroin Cytoplasm Cell exterior 2K + 3Na + ATP ADP

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molecules can be endocytosed. The user will take increasing amounts of the drug to achieve the same high, eventually resulting in an overdose and death.Chapter 3 1.2º β barrel 4º Interactions between polypeptides 1º Sequence of amino acids 3º 3-D structure of polypeptide 2º α helix 4º heterodimer Super-2º helix-loop-helix 1º asp-leu-tyr 2.a.cis proline. The bend of the proline backbone in the cis conformation is very amenable to the sharp turn if the -bend. In the trans conformation, the backbone is more linear. The rigidity of the proline residue holds the backbone more in place for this amino acid.b.cis double bonds are more common in the unsaturated fatty acids found in membrane phospholipids. This conformation provides the kink seen in the fatty acid tail, which prevents the phospholipids from packing tightly.

3.No. Histidine is too large to fit in a tight -bend, and its backbone structure does not make the same tight turn as that of cis proline.

4.Hydrogen bonds lend stability to the secondary structures. For all three 2º described in the text, hydrogen bonding occurs between the double bonded oxygen of one peptide bond with the NH portion of another peptide bond.

5.Polypeptides are the connection of many amino acids via peptide linkages. Proteins are polypeptides that have functions.

6.Glycine has the smallest side group so there is the least amount of steric hindrance. Proline, in the cis conformation, has a geometry that lends itself to the sharp turn if a -bend.

7.SDS will denature the protein and coat it with a relatively uniform concentration of negative charge.

8.Soaps will come into contact with divalent cations and precipitate out of solution.

9.Triton is a non-ionic detergent, so it would not migrate during gel electrophoresis.

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