23. Protein translation begins:
(A) at the replication fork.
(B)on the
(C)at the start codon. 
(D) in nucleus.
(E) All of these

19. Which contain(s) a phosphoanhydride bond? (A) DNA(B)RNA (C) protein (D) ATP (E) Both DNA and RNA

20. Supercoiling of DNA: (A) is not observed in prokaryotes. (B) requires the action of topoisomerase enzymes. (C) does not require ATP. (D) is not observed in eukaryotes. (E) None of the above is true.

21. What is the main damaging effect of UV radiation on DNA? (A) Depurination (B) Deamination(C)Formation of thymine dimers (D) Single strand break (E) Dehydration

22. The binding of lac repressor to DNA could be considered to be analogous to: (A) competitive inhibition of an enzyme. (B) mixed-type inhibition of an enzyme. (C) uncompetitive inhibition of an enzyme. (D) allosteric effects in enzyme regulation. (E) None of the above

24. Eukaryotic mRNA binding to the ribosomes is facilitated by_______. (A) the Shine Dalgarno sequence (B) the 7-methyl guanosine cap (C)tRNA(D) snRNA (E) All of the above

25. Cellulose fibers resemble with the protein structure in the form of: (A) β-sheets. (B) α-helices. (C) β-turns. (D)AII of the above(E) both β-sheets and u-helices. 

26. Which description is correct? (A) Organisms which could use light as energy source are classified as autotrophs. (B) Microtubules and intermediate filaments help to produce motion of organelles or of the whole cell. (C) Isoleucine has four stereoisomers. (D) H.O in liquid water forms more hydrogen bonds than in ice. (E) I M NaCl and 1 M H.SO, has the same osmolarity.

27. A teacher synthesized a peptide and asked his students to describe the amino acid residues in the peptide. Student A said: "This peptide contains the amino acid residue which might be phosphorylated". Student B said: "This peptide contains the amino acid residue which has 2 chiral centers". Student C said: "This peptide does not contain the amino acid residue which could be cleaved by CNBr'. Student D said: "This peptide does not contain the amino acid residue which could be modified with N-linked glycan in glycoproteins. Student E said: "The pI of this peptide is around 7". The sequence of this peptide should be: (A) ASQHPIMLWG (B) CVKILVGAEQNR(C) AVEFFTRDQPHK(D) AYKLWPIEAGQA (E) RGDSSERTVVNCA

複選題28. Please choose the correct answer(s) from the following descriptions:  1. Fructose is not reducing sugar.  2. The α-D-glucose and β-D-glucose interconvert in aqueous solution. 3. GIc(β1→4)Glc could be draw as the following figure.  4. The sugar drawn above is a maltose. 5. Mannose is a C2 epimer of galactose. (A) Only land 2 are correct. (B) 1, 3, and 4 are correct. (C)1 and 5 are correct.(D) 2, 3, and 4 are correct. (E) Only 5 is incorrect.

29. A protein mixture contains proteins A, B, and C (Protein A: homodimer M. = 140,000, pI 8； Protein B: Mr = 113,000, pI 5； Protein C: Mr = 13,000, pI 9). 1. Sandy used SDS-PAGE to separate theses three proteins. The sequence of the protein bands shown in gel from top to bottom is A-B-C. 2. Simon dissolved the protein mixture in 20 mM phosphate buffer (pH 7) and loaded to a cation exchange column equilibrated with the same buffer. Protein B could not bind to the column.  3. Samuel dissolved the protein mixture in 20 mM phosphate bufter (pH 7) and loaded to an anion exchange column equilibrated with the same buffer. Only protein A and C could bind to the column. 4. Silvia used a gel filtration column to separate them, C will be eluted first.  5. Sophie used 2-Dimensional electrophoresis to separate them. The relative positions of these three proteins is like the image below.  (A) 1, 2, and 5 are correct. (B) 2 and 4 are incorrect. (C) 1, 3, and 4 are incorrect.(D) Only 2 is correct.  (E) Only land 3 are incorrect.