17. The function of gap junctions is to ______.
(A) hold epithelia together
(B) seal the space between cells
(C) provide direct communication between cells
(D) All of the above
(E) None of the above

13. Electron transport and oxidative phosphorylation are performed by protein complexes in the mitochondrial ______. (A) inner membrane (B) outer membrane (C) intermembrane space (D) matrix (E) Both a and c

14. The GTP bound to ẞ-tubulin hydrolyzes to GDP and Pi ______. (A) during formation of the α-β dimer (B) during polymerization of dimers onto microtubules (C) following polymerization but before depolymerization (D) during depolymerization of dimers from microtubules (E) following depolymerization of dimers from microtubules

15. Intermediate filaments function in ______. (A) cell motility (B) providing mechanical strength for cells (C) nuclear pore structure (D) All of the above (E) None of the above

16. Active transport is transport ______. (A) of all molecules simultaneously, against their concentration gradients, across the membrane (B) in an energetically favorable direction coupled to the hydrolysis of ATP (C) in an energetically unfavorable direction always driven by hydrolysis of ATP (D) in an energetically unfavorable direction always coupled to another reaction or source of energy (E) in an energetically unfavorable direction driven only by the flow of another molecule across a membrane

18. Protein kinase A is activated by ______. (A) binding of cAMP to its catalytic subunits (B) binding of cAMP to its regulatory subunits (C) phosphorylation of its catalytic subunit (D) phosphorylation of its regulatory subunits (E) binding of G protein subunits to its regulatory subunits

19. Nuclear envelope breakdown occurs at the _ of _. (A) end; prometaphase (B) end; metaphase (C) beginning; anaphase (D) beginning; prophase (E) end; prophase

20. A proto-oncogene is a gene ______. (A) from a normal cell from which an oncogene can arise (B) that has been picked up by an oncogenic virus (C) that is in the process of evolving into an oncogene (D) that is expressed abnormally in a tumor cell (E) that has been mutated to alter cell growth control

1. How many significant figures should be reported for the answer to the following calculation? (1.0045 – 0.0013) (A) 1 (B) 2 (C) 3 (D) 4 (E) 5

2. Which of these atoms does not obey the octet rule? (A) S in SF4 (B) Si in SiCl4 (C) P in PC13 (D) N in N2 (E) None of the previous answers

3. In which of these molecules does carbon have an oxidation state of 0? (A) CO2 (B) H2CO (C) CH4 (D) HCCl3 (E) None of the previous answers