N terminal signal sequence

30. Proteins destined for secretion are first imported into the Golgi from the cytosol.

(a) True (b) False

31. BiP is an HSP70 chaperone protein that binds proteins as they are entering the ER lumen, and assists folding and translocation.

(a) True (b) False

32. An ER membrane protein that has an N-terminal signal sequence and a single stop transfer sequence will

(a) span the membrane once, with the N-terminus of the protein in the ER lumen.

(b) span the membrane twice, with the N-terminus of the protein in the ER lumen.

(c) span the membrane once, with the N-terminus of the protein in the cytosol.

(d) span the membrane twice, with the N-terminus of the protein in the cytosol.

33. Small membrane-enclosed sacs that can store or transport substances are called

(a) Particles (b) Signals

(c) Macrosomes (d) Vesicles

34. Which of the following is NOT a possible target of proteins imported into the ER?

(a) ER (b) Golgi

(c) Plasma membrane (d) Mitochondria

35. A post-translational modification that occurs in the ER is

(a) Removal of mannose (b) AIDition of N-acetylglucosamine

(c) N-linked glycosylation (d) AIDition of mannose-6-phosphate

36. Which of the following is NOT the way proteins are transported through the Golgi?

(a) Vesicles bud from one compartment and fuse with the next.

(b) Proteins travel from Cis-Golgi Network, to Cis, to Medial, to Trans, to Trans-Golgi-Network.

(c) Proteins travel from Cis, to Medial, to Trans, to Cis-Golgi Network.

(d) Each compartment (“cisterna”) matures into the next.

37. Clathrin-coated vesicles bud from the ER and fuse with the Golgi.

(a) True (b) False

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38. Which of the following statements about Sar1 is TRUE?

(a) Sar1 is activated by a membrane-bound GAP.

(b) Sar1 triggers vesicle formation by inducing membrane curvature and recruiting vesicle coat

proteins.

(c) Activation of Sar1 exposes a hydrophobic tail that releases the protein from the vesicle

membrane.

(d) When active, Sar1 is bound to GDP.

39. The name of the GTPase (AKA small G protein) that is involved in tethering a donor vesicle

with its target is

(a) Rab (b) Rob

(c) SNARE (d) Sar1

40. The signal that allows soluble ER-resident proteins to be retrieved from the Golgi is

(a) KKXX (b) KDEL

(c) M-6-P (d) COPII

41. The pH of the lysosome (lumen) is

(a) 7 (b) 6

(c) 5 (d) 4

42. Patients with I-cell disease have non-functional lysosomes. Why?

(a) Acid hydrolases in the lysosome contain mutations that render them functionally inactive.

(b) The pH of the lysosome is not acidic enough.

(c) Acid hydrolases are secreted rather than targeted to the lysosome.

(d) The pH of the lysosome is too acidic.

43. Which of the following choices reflects the appropriate order through which a protein

destined for the plasma membrane travels?

(a) lysosome ? endosome ? plasma membrane

(b) ER ? lysosome ? plasma membrane

(c) Golgi ? lysosome ? plasma membrane

(d) ER ? Golgi ? plasma membrane

44. The pathway for proteins targeted to the lysosome by endocytosis is

(a) Plasma membrane, late endosome, early endosome, lysosome.

(b) Plasma membrane, Trans-Golgi-Network, late endosome, lysosome.

(c) Plasma membrane, early endosome, late endosome, lysosome.

(d) Plasma membrane, secretory vesicle, Trans-Golgi-Network, lysosome.

45. The process by which worn-out organelles are recycled is called

(a) phagocytosis (b) pinocytosis

(c) autophagy (d) endocytosis

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46. The endosome compartments and the lysosome are acidified by

(a) sodium-proton symporters. (b) proton ATPases.

(c) ATP synthases. (d) calcium-proton antiporters.

47. Clathrin triskelions are composed of three clathrin heavy chains and three clathrin light

chains.

(a) True (b) False

48. Which of the following statements about vesicle buIDing from the Golgi is FALSE?

(a) Clathrin molecules are important for binding to and selecting cargos for transport.

(b) Adaptins interact with clathrin.

(c) Once vesicle buIDing occurs, clathrin molecules are released from the vesicle.

(d) Clathrin molecules act at the cytosolic surface of the Golgi membrane.

49. Which of the following is FALSE about cholesterol uptake from the bloodstream?

(a) Cholesterol is associated with LDL (low density lipoprotein).

(b) The LDL receptor is located on the plasma membrane.

(c) Within the endosome, low pH causes LDL to dissociate from the receptor.

(d) The LDL and the receptor are degraded in the lysosome.

50. Which of the following is NOT a possible fate of molecule endocytosed from the plasma

membrane?

(a) recycled to the original membrane (b) destroyed in the lysosome

(c) transported to the ER (d) transcytosed to a different membrane