I have trouble answering these questions. Would you please help me on these? You
ID: 166546 • Letter: I
Question
I have trouble answering these questions. Would you please help me on these?
You are studying post-translational translocation of a protein into purified microsomes, but you find that import is very inefficient. Which one of the following might be expected to increase the efficiency of import if added to the mixture of protein and microsomes?
BiP
Cytosolic Hsp70
Free ribosomes
Sec61 complex
SRP
Protein synthesis occurs in which of the following cellular compartments?
The cytosol, mitochondrial matrix, stroma of plastids, rough ER, Golgi apparatus
The cytosol, mitochondrial matrix, thylakoid sacs of plastids, rough ER
The cytosol, mitochondrial matrix, stroma of plastids, rough ER
The cytosol, mitochondrial matrix, stroma of plastids, rough ER, lysosomes
The cytosol, the cytosol of bacteria, stroma of plastids, Golgi apparatus
How many different locations can proteins be directed to in chloroplasts?
4
5
6
7
8
How many different locations can proteins be directed to in mitochondria?
2
3
4
5
6
a.BiP
b.Cytosolic Hsp70
c.Free ribosomes
d.Sec61 complex
e.SRP
Explanation / Answer
Answer 1. “e”
The given information is that “import is inefficient.” Import occurs when SRP binds to the protein. Then this SRP +protein complex binds to receptor on Sec-61 complex. After binding to receptor, the complex opens up, so that protein goes inside the microsomes.
So, import requires three things: SRP, Sec-61 complex and the protein. Now, protein and Sec-61 complex (microsomes) have already been added. There seems to be deficiency of SRP. Therefore, adding SRP will increase import.
Answer 2. “c”
Protein synthesis occurs on ribosomes. So, wherever ribosomes are present, protein synthesis will occur.
Ribosomes are present in the cytosol, mitochondrial matrix, stroma of plastids, rough ER
Answer 3. “b”
The proteins are formed by ribosomes of stroma. Once formed they can be taken to thylakoids, grana lamellae, inter membrane space, outer membrane, ribosomes of the stroma. So, there are 5 locations.
Answer 4. “b”
In mitochondria, proteins are formed in matrix. From here, they can be directed to inner mitochondrial membrane, inter membrane space, outer mitochondrial membrane, towards ribosomes of matrix. So, there are 4 locations where proteins can be directed to.