複選題

3. Acidification of endosomes is important in dissociating
(A) cholesterol from LDL.
(B) iron from transferring.
(C) transferrin from the transferrin receptor.
(D) None of the above
(E) All of the above

49. The force that drives an ion through a membrane channel depends upon: (A) the charge on the membrane. (B) the difference in electrical potential across the membrane. (C) the size of the channel. (D) the size of the ion. (E) the size of the membrane.

50. Ubiquitin is a: (A) component of the electron transport system. (B) protease. (C) protein kinase. (D) protein phosphorylase. (E) protein that tags another protein for proteolysis.

1. Which of the following statements regarding cytoskeleton is correct? (1) ATP or GTP hydrolysis is required for microfilaments or microtubules assembly. (2) Tubulin isotypes differ primarily at their amino terminus.  (3) Phosphorylation of lamins during mitosis drives the disassembly of the nuclear envelope. (A) (1) only (B) (1) and (2) (C) (2) and (3) (D) (1) and (3) (E) All of above

2. Which of the following statements regarding G protein or G protein-mediated signal transduction is false? (1) GTP binds the beta submit of the trimeric G proteins. (2) C-terminus of G protein-coupled receptor is on the cytoplasmic face of the membrane.  (3) Epinephrine binding to the b-adrenergic receptor causes an activation of adenylyl cyclase through the activation of a stimulatory G protein. (A) (1) (B) (2) (C) (3) (D) (1) and (3) (E) (2) and (3)

4. Which of the following statements regarding stem cells is correct? (1) A stem cell divides to a copy of itself and to a differentiated cell or a cell capable of differentiating into multiple cell types. (2) Differentiation potential hight to low: pluripotent stem cells ＞ totipotent stem cells ＞ multipotent stem cells. (3) Induced pluripotent stem cells can differentiate into any of the 3 germ layer cells. (A) (1) (B) (2) (C) (3) (D) (1) and (3) (E) (2) and (3)

5. In the mouse embryo, pluripotent stem cells are found in the (A) inner cell mass. (B) trophectoderm. (C) zona pellucida. (D) blastocoel. (E) inner cell mass and blastocoel.

6. Which of the following is not part of RNA processing in eukaryotes? (A) Addition of a 5'cap (B) Addition of a polyA. tail (C) Intron removal (D) Splicing of exons (E) Reverse transcription

7. Cellular iron homeostasis is accomplished by the coordinated regulated expression of the transferrin receptor and ferritin, which mediate iron uptake and storage, respectively. There are iron responsive element (IRE) in the 5' UTR of ferritin mRNA and in the3' UTR of transferrin receptor mRNA. (1) IRE-binding proteins bind to IREs of ferritin mRNA to inhibit translation in lower iron concentration；  (2) IRE-binding proteins bind to IREs of ferritin mRNA to inhibit translation in higher iron concentration； (3) IRE-binding proteins bind to IREs of transferrin receptor mRNA to stabilize mRNA in lower iron concentration； (4) IRE-binding proteins bind to IREs of transferrin receptor mRNA to stabilize mRNA in higher iron concentration. Which are correct? (A) (1) and (3) (B) (2) and (4) (C) (1) and (4) (D) (2) and (4) (E) all are incorrect

8. The following: (1). histone acetylation； (2). H3K4me (histone3 lysine4 methylation)； (3).H3K9me (histone3 lysine9 methylation)； (4).H3K27me (histone 3 lysine 27 methylation)； (5). DNA methylation； (6). HDAC (histone deacetylase)； (7). HAT (histone acetyltransferase). Which are related to gene activation? (A) (1), (2) and (7) (B) (1), (3), (4) and (6) (C) (1), (2), (3), (4), (5) and (6) (D) (3), (4), (5) and (6) (E) (1) and (7)

9. In prokaryotes, protein synthesis rates are limited by the rates of mRNA synthesis. RNA synthesis occurs at about 60 nucleotides/sec. Therefore, protein synthesis occurs at about amino acids/sec. (A) 10 (B) 15 (C) 20 (D) 30 (E) 60