Protein X contains four transmembrane domains, a short N-terminus and a long C-terminus. Following protein synthesis, the N-terminus of the protein faces the lumen (the inside) of the ER. After protein X is transported to the cell surface via exocytosis, you would expect the N-terminus of protein X to be
A. extracellular.
B. cytoplasmic.
C. in the lumen.
D. in the lipid bilayer of the plasma membrane.
Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
Gather Content
· What do you know about how proteins are oriented in a membrane? What other information is related to the question?
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
A. extracellular.
Clarify Question
· What is the key concept addressed by the question?
o The question asks about the orientation of a protein in a membrane.
· What type of thinking is required?
o You are being asked to apply your knowledge of how proteins are oriented in a membrane and the process of exocytosis.
Gather Content
· What do you know about how proteins are oriented in a membrane? What other information is related to the question?
o When a protein is made in the endoplasmic reticulum, the part facing the inside is said to be in the lumen. Proteins move from the endoplasmic reticulum to the plasma membrane through small lipid vesicles that pinch off the endoplasmic reticulum. Proteins facing the lumen will remain on the inside of these vesicles. When the vesicles fuse with the plasma membrane it is like a bubble popping and the contents inside the vesicle will now be outside of the cell. Similarly the proteins in the membrane will now be facing outside of the cell.
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
o Proteins on the inside or lumen of the endoplasmic reticulum will be on the extracellular or outside of the membrane after being transported through vesicles.
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
o This question asked you to apply your knowledge of how proteins are oriented in a membrane. If you got the correct answer, great job! If you got an incorrect answer, where did the process break down? Did you think that proteins on the inside of a vesicle remained on the inside of a cell when it fused with the plasma membrane? Did you think that the protein would be buried in the lipid bilayer?
You might also like to view...
________ molecules deliver amino acids to ribosomes during translation.
A. Ribosomal RNA (rRNA) B. Transfer RNA (tRNA) C. Messenger RNA (mRNA) D. Heterogeneous nuclear RNA (hnRNA)
In the open ocean, ________.
A. Archaea are not present B. Archaea are only found in extreme environments such as near thermal vents C. the relative abundance of Archaea versus Bacteria decreases with depth D. the relative abundance of Archaea versus Bacteria increases with depth
Two strains of S. cerevisae (yeast) are crossed. One has the genotype ABC and the other abc. Five sets of the resultant tetrads are noted below. In which set did a gene conversion event occur?
A) abc, aBc, AbC, aBC B) abc, abc, ABC, ABC C) aBc, aBc, AbC, AbC D) abC, abc, ABc, ABC E) Abc, Abc, aBC, aBC
How long can it take for a full stomach to empty?
a. 1?2 hours b. 2?4 hours c. 2?6 hours d. 4?8 hours e. 6?8 hours