A protein that has been transported past the outer chloroplast membrane would have to pass how many more membranes to reach the stroma and thylakoid lumen, respectively?

Question

A.  0,1
B.  1,2
C.  2,3
D.  3,4

Clarify Question
What is the key concept addressed by the question?
What type of thinking is required?

  Gather Content
What do you already know about chloroplasts and membranes? What other information is related to the question?
   Choose Answer
Do you have all necessary information to determine what was produced during the plant experiment?

  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? 

Answer 1

B.  1,2

Clarify Question
What is the key concept addressed by the question?
        · The question asks you to determine how many more chloroplast membranes would be required for a protein to be transported into the thylakoid lumen once it is already past the outer chloroplast membrane?
What type of thinking is required?
        · You are being asked to use what you already know about chloroplasts and membranes, and apply that to figure out how many more membranes a protein inside the outer chloroplast membrane would need to pass through to get to the inside of the thylakoid lumen.

  Gather Content
What do you already know about chloroplasts and membranes? What other information is related to the question?
        · Let’s first re-orient you to chloroplast structure and function. Chloroplasts are the cellular organelle involved in photosynthesis. They are enclosed by multiple membranes, each of which serves to compartmentalize the interior of the chloroplast.
        · The innermost membrane, called the thylakoid membrane, contains a dense concentration of proteins and chlorophyll molecules that capture sunlight and use it to drive the process of photosynthesis. For example, the thylakoid membrane constituents produce both ATP and NADPH. The thylakoid membrane also maintains an impermeable barrier to protons, the positively charged subatomic particles used to generate the proton gradient needed to produce ATP. What other membranes are associated with the chloroplast, and how many would a protein that is already inside the outer chloroplast membrane need to pass through to get to the thylakoid lumen?
   Choose Answer
Do you have all necessary information to determine what was produced during the plant experiment?
        · Once you understand chloroplast anatomy it’s fairly straightforward to figure out the answer. Chloroplasts have an outer membrane, and inner membrane, and a thylakoid membrane. In this particular question, the protein has already passed through the outer chloroplast membrane and is in the space just outside of the inner mitochondrial membrane.
        · So, in order to be transported into the thylakoid lumen, the protein must pass through the inner chloroplast membrane and the thylakoid membrane, bringing the total number of membranes that need to be passed through to two.

  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?         · Answering this question correctly depended on your ability to apply what you know about chloroplast anatomy and the number of membranes included in a chloroplast to determine how many more membranes a protein would need to cross in order to get into the thylakoid lumen.
        · If you got the correct answer, well done! If you got an incorrect answer, were you able to determine the total number of membranes in the chloroplast? Were you able to spatially position the protein in the space between the outer and inner chloroplast membranes? Were you able to count the remaining number of membranes needed to get to the thylakoid lumen?