27. Which of the following techniques was NOT used to determine the three-dimensional structure of
(A) NMR spectroscopy
(B) X-ray diffraction
(C) Cryogenic electron microscopy
(D) UV/Vis spectroscopy
(E) All of the above

23. Enzymes are biological catalysts that enhance the rate of a reaction by: (A) decreasing the activation energy. (B) decreasing the amount of free energy released. (C) increasing the activation energy. (D) increasing the amount of free energy released. (E) increasing the energy of the transition state.

24. To determine the isoelectric point of a protein, first establish that a gel: (A) contains a denaturing detergent that can distribute uniform negative charges over the protein's surface. (B) exhibits a stable pH gradient when ampholytes become distributed in an electric field. (C) is washed with an antibody specific to the protein of interest. (D) neutralizes all ionic groups on a protein by titrating them with strong bases. (E) relates the unknown protein to a series of protein markers with known molecular weights, Mr.

25 Which of the following lipids can be formed by the methylation of phosphatidylethanolamine? (A) Phosphatidylinositol (B) Phosphatidylcholine (C) Phosphatidylserine (D) Sphingomyelin (E) Lysophosphatidylcholine

26. Which volatile short-chain fatty acid is believed to lower serum cholesterol by acting as an inhibitor of cholesterol biosynthesis? (A) acetic (B) butyric (C) propionic (D) palmitic (E) lauric

28. Which of these statements is generally true of integral membrane proteins? (A) A hydropathy plot reveals one or more regions with a high hydropathy index. (B) The domains that protrude on the cytoplasmic face of the plasma membrane nearly always have covalently attached oligosaccharides. (C) They are unusually susceptible to degradation by trypsin. (D) They can be removed from the membrane with high salt or mild denaturing agents. (E) They undergo constant rotational motion that moves a given domain from the outer face of a membrane to the inner face and then back to the outer.

29.In a newly discovered electron transport complex a researcher has identified the redox center Fe-S, cytochrome c, and coenzyme Q. The researcher also knows that this complex ultimately passes its electrons to oxygen. What is most likely the redox center which completes this task? (A) Fe-S (B) 2Fe-2S (C) coenzyme Q (D) cytochrome c (E) None of the above protein?

30. Which of the following pairs of sugars are epimers of each other? (A) D-sorbose and D-fructose (B) D-sorbose and D-xylulose (C) D-arabinose and D-ribose (D) D-fructose and L-fructose (E) D-ribose and D-ribulose

31. Which description of fungi is correct? (A) Ascomycota: Multinucleate hyphae lack septa (B) Glomeromycota: Form arbuscular mycorrhizae (C) Ascomycota: In sexual reproduction, four ascospores are formed inside a sac called an ascus (D) Basidiomycota: In sexual reproduction, eight basidiospores are borne on a club-shaped basidia (E) Zygomycota: the heterokaryotic (dikaryotic) stage can be found in the life cycle

32. Developmentally, which type of human tooth is most similar to ivory(象牙)? (A) incisor (B) canine (C) premolar (D) molar (E) third molar (wisdom tooth)

33. How many photons are required to generate one O2 molecule during photosynthesis light reaction? (A) 2 (B)4(C)8(D) 12 (E) 16