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Home Q & A Board Biology-Related Homework Help Cell Biology
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crooked_horizon crooked_horizon
wrote...
Go to Answer
10 years ago
I need some help with this problem. I don't know where to start.
Knowing the protein content (number of molecules/ relative concentration) within a plasma membrane can provide information about a cell's function. Membrane-associated proteins can be easily isolated from plasma membranes and separated by SDS-PAGE. The proteins are visualized with a dye (Coomassie Blue) whose intensity of color is roughly proportional to the mass of protein present and quantitative estimates can be made as shown in the table below.

Melanopsin has a MW of 275,000 (g/mol) and abosrbed 20% of stain.
Trp 1 has a MW of 125,000 (g/mol) and abosrbed 40% of stain.
Girk 2 has a MW of 20,000 (g/mol) abosrbed 3.4% of stain.


a) Using the table above, calculate the number of molecules of Melanopsin, Trp1 and Girk2 in an individual cell. Assume that 1 ml of cell lysates contain 1010 cells and 5 mg of total membrane protein. Show your work. (Hint: will need to use Avogadro's Number = 6 x 1023 mol -1)

So I'm going from MW of Melanopsin-->molecules in 1 cell.
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wrote...
#1
10 years ago
Just need to find the % molecular mass and divide by the lowest to find the empirical formala
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slayerstzainslayerstzain
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10 years ago
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Second S. Author
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#3
10 years ago
Quote from: slayerstzain (10 years ago)
Avogadro's number tells you 6x10^23 (molecules/mol). Divide by the MW (gram/mol) and you'll end up with (molecules/gram). Now you need to use the percentage of stain to find out how many grams of each protein are found per cell. For melanopsin, find 20% of 5 mg then convert it to grams. Divide by the number of cells you have and you'll end up with X (melanopsin grams/ cell). Multiply this number with the previous number you had of (molecules/gram) and you will find how many molecules per cell. Repeat this for the other two proteins.

They told you 1ml of cell lysates though. So if you were told to use more or less than 1ml then you have to change the total grams of protein and total number of cells accordingly.

Thanks for the reply!
So I get the first part...

6x10^23 (molecules/mol) ÷ 275,000 (g/mol) = 2.18 * 10^18 molecules/gram.

20% of 5 mg = 1 mg= .001 g

But I don't know the number of cells I have? How do I get melanopsin grams/cell.


wrote...
#4
Educator
10 years ago
Is this the same question here: https://biology-forums.com/index.php?topic=101243.0
wrote...
#5
10 years ago
Quote from: Second Step? (10 years ago)
Quote from: slayerstzain (10 years ago)
Avogadro's number tells you 6x10^23 (molecules/mol). Divide by the MW (gram/mol) and you'll end up with (molecules/gram). Now you need to use the percentage of stain to find out how many grams of each protein are found per cell. For melanopsin, find 20% of 5 mg then convert it to grams. Divide by the number of cells you have and you'll end up with X (melanopsin grams/ cell). Multiply this number with the previous number you had of (molecules/gram) and you will find how many molecules per cell. Repeat this for the other two proteins.

They told you 1ml of cell lysates though. So if you were told to use more or less than 1ml then you have to change the total grams of protein and total number of cells accordingly.

Thanks for the reply!
So I get the first part...

6x10^23 (molecules/mol) ÷ 275,000 (g/mol) = 2.18 * 10^18 molecules/gram.

20% of 5 mg = 1 mg= .001 g

But I don't know the number of cells I have? How do I get melanopsin grams/cell.




It says it in the OP. 1010 cells which I assume means 10^10 cells.
wrote...
#6
10 years ago
Quote from: slayerstzain (10 years ago)
Quote from: Second Step? (10 years ago)
Quote from: slayerstzain (10 years ago)
Avogadro's number tells you 6x10^23 (molecules/mol). Divide by the MW (gram/mol) and you'll end up with (molecules/gram). Now you need to use the percentage of stain to find out how many grams of each protein are found per cell. For melanopsin, find 20% of 5 mg then convert it to grams. Divide by the number of cells you have and you'll end up with X (melanopsin grams/ cell). Multiply this number with the previous number you had of (molecules/gram) and you will find how many molecules per cell. Repeat this for the other two proteins.

They told you 1ml of cell lysates though. So if you were told to use more or less than 1ml then you have to change the total grams of protein and total number of cells accordingly.


Thanks for the reply!
So I get the first part...

6x10^23 (molecules/mol) ÷ 275,000 (g/mol) = 2.18 * 10^18 molecules/gram.

20% of 5 mg = 1 mg= .001 g

But I don't know the number of cells I have? How do I get melanopsin grams/cell.




It says it in the OP. 1010 cells which I assume means 10^10 cells.

Yea I figured it out. That was  a dumb question. It has 21800 molecules. Thanks for the help!!
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