2. The nitrogen-fixing activity of cyanobacteria takes place in
(A) thylakoid
(B) heterocyte
(C) chloroplast
(D) plasmid
(E) endospore

23. Which of the following is most soluble in water (A) (B) (C) (D) (E)

24. In the complex ion , the oxidation number of Co is (A) +1 (B) +2 (C)+3 (D) -2 (E) -1

25. Which complex has the less unpaired electrons (A) (B) (C)Na3[CoCl6] ； (D) [Cr(NH3)3(H2O)Cl2]Cl (E)

1. Aquaporins (A) allow water to cross the plasma membrane via facilitated diffusion. (B) allow water to cross the plasma membrane against its concentration gradient. (C) allow for the active transport of water. (D) are found in all cells. (E) all are correct.

複選題3. Which substance could be an enzyme cofactor? (A) protein (B) polypeptide (C) zinc atom (D) ribosome (E) vitamin

4. How does inhibition of an enzyme-catalyzed reaction by a competitive inhibitor differ from inhibition by a noncompetitive inhibitor? (A) Competitive inhibitors interfere with the enzyme； noncompetitive inhibitors interfere with the reactants. (B) Competitive inhibitors bind to the enzyme reversibly； noncompetitive inhibitors bind to it irreversibly. (C) Competitive inhibitors change the enzyme's tertiary structure； noncompetitive inhibitors cause polypeptide subunits to dissociate. (D) Competitive inhibitors bind to the active site of the enzyme； noncompetitive inhibitors bind to a different site. (E) Noncompetitive inhibitors bind to the active site of the enzyme； competitive inhibitors bind to a different site.

5. Which statement regarding the function of mitosis is false? (A) Mitosis allows organisms to grow. (B) Mitosis promotes genetic diversity. (C) Mitosis is necessary for asexual reproduction in eukaryotes. (D) Mitosis promotes repair tissues. (E) All are incorrect.

6. Mendel's law of independent assortment states that (A) chromosomes sort independently of each other during mitosis and meiosis. (B) independent sorting of genes produces polyploid plants under some circumstances. (C) the allele that a gamete receives for one gene does not influence the allele the gamete receives for another gene. (D) genes are sorted concurrently during gamete formation. (E) genes are transmitted to progeny.

7. Which of the following statement is True for a virulent phage? (A) phage replicates without destroying host cell (B) phage genome integrates in the chromosome of bacteria (C) a large number of phages are released (D) bacterial cell contains phage DNA (E) all statements are true

8. What results from conjugation between a bacterium that lacks an F factor (F−) and a bacterium that has an F factor on its chromosome (F+)? (A) The F− bacterium ends up carrying one or more plasmids from the F+ bacterium； the F+ bacterium is unchanged. (B) The F+ bacterium ends up with a recombinant chromosome that carries some genes from the F− bacterium, and the F− bacterium ends up with an unaltered chromosome. (C) The F+ bacterium ends up with a recombinant chromosome that carries some genes from the F− bacterium, and the F− bacterium ends up with a chromosome that lacks those genes. (D) The F− bacterium ends up with a recombinant chromosome that carries some genes from the F+ bacterium, and the F+ bacterium ends up with an unaltered chromosome. (E) The F+ bacterium ends up with a recombinant chromosome that carries some genes from the F− bacterium, and the F+ bacterium ends up with an unaltered chromosome.