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.

複選題46. After the ligand binding to PAR, which of the following events will happen? (A) The receptors form dimer on the membrane. (B) The receptors will be tyrosine-phosphorylated. (C) The receptor will dimerize with RXR and illicit gene transcription. (D) It activates GTP binding proteins and increase calcium mobilization. (E) It contains DNA- and ligand-binding domains in distinct region of PAR.

47. Some hormones are derived from amino acids； for example, catecholamines are derived from while NO is derived from _____ (A) tyrosine； arginine (B) tryptophan； lysine (C) tyrosine； histidine (D) tryptophan； arginine (E) histidine； lysine

48. Hormone-activated phospholipase C can convert phosphatidylinositol 4,5-bisphosphate to: (A) diacylglycerol + inositol triphosphate. (B) diacylglycerol + inositol + phosphate. (C) glycerol + inositol + phosphate. (D) glycerol + phosphoserine. (E) phosphatidyl glycerol + inositol + phosphate.

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.

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)

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

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