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

43. The ligands for peroxysome proliferator-activator receptor (PPAR) belong to which of the following categories. (A) protein (B) vitamin (C) fatty acid (D) amino acid (E) carbohydrate

44. Cholera toxin, a protein produced by a gram-negative bacterium vibrio cholerae, is responsible for the characteristic symptoms of cholera: extensive loss of body water and Na⁺ through continuous, debilitating diarrhea. If body fluid and Na⁺ are not replaced, severe dehydration results； untreated, the disease is often fatal. What is the effect of cholera toxin in the intestinal cells? (A) Increase GTP hydrolysis. (B) Persist activation of G protein. (C) Increase the degradation of cGMP. (D) Increase the rate of phophatidylinositol turnover. (E) Open the chloride channels on the membrane of intestinal cells. 

45. According to the description, which of the following compounds could illicit proliferation signaling in smooth muscle cells? (A) thrombin (B) vitamin K (C) interferon (D) cholesterol (E) retinoic acid

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.

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.

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)

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