What is the Molar Mass of an Enzyme with a Given Osmotic Pressure?

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Discussion Overview

The discussion revolves around calculating the molar mass of an enzyme based on a given osmotic pressure, focusing on a specific homework problem involving a 2.02-g sample in a 6.00-mL solution at 298K with an osmotic pressure of 0.123 atm. The context is primarily homework-related and involves mathematical reasoning.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant presents a calculation using the formula for osmotic pressure (pi = MRT) to find the molar mass of the enzyme, arriving at approximately 66976 g/mol.
  • Another participant confirms the calculation but expresses concern about the unusually high value, suggesting they may be missing something.
  • A third participant agrees with the calculated answer and notes that the value is approximately 67,000 g/mol, which they assert is within the typical range for enzymes.
  • Another participant supports the high molar mass, indicating that large values are expected for enzymes.

Areas of Agreement / Disagreement

Participants generally agree on the calculated molar mass being high but within the expected range for enzymes. There is some uncertainty expressed regarding the calculation process, but no consensus on any potential errors or alternative interpretations.

Contextual Notes

Participants do not explicitly address any assumptions or limitations in the calculations, nor do they clarify the implications of the unusually high molar mass in the context of enzyme characteristics.

Who May Find This Useful

Students or individuals interested in biochemistry, particularly those studying enzyme properties and calculations related to osmotic pressure and molar mass.

Benzoate
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Homework Statement



A 2.02-g sample of an enzyme is used to make a 6.00-mL solution. What is the molar mass of the enzyme if the osmotic pressure of the solution at 298K is 0.123 atm? Note that enzymes are nonelectrolytes

Homework Equations



pi=MRT , R=.0821 L*atm*K^1-*mol^1-

The Attempt at a Solution



pi=MRT => pi/RT=M=.123 atm/(298K)(.0821)=.00503 M

to find molar mass, I'd want to convert my concentration into grams/mol

.00503 M =.00503 mmol/1 mL
multiply (.00503 mmol/1mL)*(6.00 mL)= .0302 mmol => .00003016 mol enzyme

so molar mass = 2.02 g enzyme /.00003016 mol enzyme = 66976. 12732 g/mol , which is unusually enormous for a typical molar mass
 
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I did the problem a few times and got the same answer. Althought it does seem high so I redid it a few times and kept getting the same answer. Maybe I'm missing something.
 
The answer looks right to me.
 
Benzoate said:
...so molar mass = 2.02 g enzyme /.00003016 mol enzyme = 66976. 12732 g/mol , which is unusually enormous for a typical molar mass


I assume that your answer is approximately 67,000 g/mol? This is 67 kilodaltons (kDa) which is well within the usual range for an enzyme.
 
i get the same, and expect big fat numbers for enzymes (as chemisttree points out)

4 to 1 :)
 

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