You have identified an enzyme that appears to be involved in the addition of palmityl group (a fatty acid) to certain proteins. Knowing that palmitoylated proteins are usually targeted for delivery to the plasma membrane, in which organelles might this enzyme be expressed?

Question

A.  Golgi apparatus and nucleus
B.  Golgi apparatus and endoplamic reticulum
C.  Endoplamic reticulum and ribosomes
D.  Endoplamic reticulum and nucleus

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
· What key words does the question contain and what do they mean?

Gather Content
· What do you know about protein transport to the plasma membrane? How does it relate to the question?

Consider Possibilities
· What other information is related to the question? Which information is most useful?

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?

Answer 1

B.  Golgi apparatus and endoplamic reticulum


Clarify Question
· What is the key concept addressed by the question?
        o The question asks about the transport of proteins to the plasma membrane.
· What type of thinking is required?
        o You are being asked to apply your knowledge of protein transport in a cell to predict the location of an enzyme involved in the process.
· What key words does the question contain and what do they mean?
        o Palmityl group (a fatty acid) – this fatty acid can be attached to proteins by specific enzymes.  Attaching a fatty acid to a protein will make it more hydrophobic and likely to be embedded in a membrane.
        o Delivery to the plasma membrane – proteins targeted for delivery to the plasma membrane are made in the endoplasmic reticulum and then move through the Golgi and on to the plasma membrane through vesicles.

Gather Content
· What do you know about protein transport to the plasma membrane? How does it relate to the question?
        o Proteins targeted for delivery to the plasma membrane are made in the endoplasmic reticulum and then move through the Golgi and on to the plasma membrane through vesicles.

Consider Possibilities
· What other information is related to the question? Which information is most useful?
        o Ribosomes are large enzymes used to synthesize proteins by translating a messenger RNA.
        o The nucleus contains DNA and is where transcription to synthesize RNA occurs.

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Proteins targeted for delivery to the plasma membrane are made in the endoplasmic reticulum and then move through the Golgi and on to the plasma membrane through vesicles.  An enzyme that attaches fatty acids to proteins targeted for the plasma membrane would be found in the endoplasmic reticulum or Golgi.  Addition of the fatty acid would make the protein more hydrophobic and bind to the membrane in the vesicle and eventually the plasma membrane.

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 understanding of protein secretion to predict where an enzyme would be found. If you got the correct answer, great job! If you got an incorrect answer, where did the process break down? Did you recall which organelles were involved in protein secretion?  Did you realize that adding a fatty acid to a protein would make the protein more hydrophobic and bind to a membrane?  Did you think that the nucleus was involved in protein secretion?