What does LDL 5mM mean?

[Rabdos]

Hello!

LDL has 3,000 kDa molecular weight which means that 1mol of it weighs 3 tonnes.

When we say for a patient that LDL is 5mM we mean that they have 5mmol per 1L of their blood.

However, 5mmol of LDL would weigh 15kg!

What's wrong?

 

[bulkbiker]

that 1mol of it weighs 3 tonnes.

I think you have some incorrect mathematics..?

 

[Mr_Pot]

The molecular weight of LDL Cholesterol is 386.654 g/mol. 5 mmol/L is equivalent to 1933.25 mg/L or nearly 2 grams. I don't recognise the units kDa

 

[Rabdos]

kiloDaltons is a molecular mass unit. 1Dalton = 1g/mol by definition.
Here it says that LDL chylomicrons are 3million Daltons.
https://en.wikipedia.org/wiki/Low-density_lipoprotein

386g/mol is the molecular weight of cholesterol itself, not of LDL

 

[JohnEGreen]

1 Da = 1 u = 1.660 539 066 60(50) ×10−27 kg,

 

[Mr_Pot]

kiloDaltons is a molecular mass unit. 1Dalton = 1g/mol by definition.
Here it says that LDL chylomicrons are 3million Daltons.
https://en.wikipedia.org/wiki/Low-density_lipoprotein

386g/mol is the molecular weight of cholesterol itself, not of LDL

Could it be that when they give a figure of 5 mmol/L it means that is the density of the cholesterol from LDL particles rather than the density of the particles themselves.

 

[Rabdos]

Okay and what is the true LDL density then?

 

[Rabdos]

1 Da = 1 u = 1.660 539 066 60(50) ×10−27 kg,

So one LDL molecule which is 3million daltons is 3 x 1.6 x 10-18 grams, so one mole is that times 6x10^23 equals 28x10^5 grams or 3tonnes, exactly what I said.

 

[Mr_Pot]

So one LDL molecule which is 3million daltons is 3 x 1.6 x 10-18 grams, so one mole is that times 6x10^23 equals 28x10^5 grams or 3tonnes, exactly what I said.

Congratulations, although I am not sure that this information is of much practical use. Of course a LDL particle isn't actually a molecule.

 

[JohnEGreen]

@Rabdos Another general knowledge quiz or test.

And you are talking about units of mass and of course you not going to have a mole of LDL circulating in your system unless of course you circulatory system can accommodate a small VW car or the like and so like many of such threads this one in any practicable sense is totally irrelevant to diabetes.

A black hole can have the mass of several suns compressed into a singularity quite interesting but also totally irrelevant.