Molecule of the month – cholesterol

 

Molecule of the month has unfortunately become more like molecule of the financial quarter of late. Apologies for that.  We are back though, and this month’s mouth-watering molecule is cholesterol.

What prompted me to write about it was when a few weeks back I attended a public lecture. This may sound dull, but before I lose you I should say that it involved being cooked a meal, live – think ready steady cook – whilst told all about the nutritional content of the dishes by an informed biologist woman. OK, maybe your first thought was correct. Slightly dull. We did get to eat the food afterwards though.

Anyway, one Indian gentleman was asking all about cholesterol. ‘I’ve heard,’ he rasped, ‘that one shouldn’t be eating eggs anymore if one has a high cholesterol level. Is that so?’

‘What?’ I thought. ‘Surely eggs are OK aren’t they? I mean, they contain cholesterol, sure, but there’s no need to be scared of them!’ Well, at least I was determined of one thing; the readers of B21 would not be such scaredy cats once I was through with them. 

Let’s start out with some basics. Cholesterol is a type of steroid. It’s also has a character a lot like that of fats. In chemistry what makes something ‘fatty’ is the proportion of non-polar groups of atoms in contains. This is defined by the type and the connectivity of the atoms. Looking at the structure of cholesterol we can see it is almost entirely composed of just carbon and hydrogen (with just one oxygen). There’s not much difference in polarity (think poles of a magnet) between carbon and hydrogen so the molecule isn’t very polar.

  

cholesterol

It might be easier to appreciate how non-polar cholesterol is looking at the 3D model below. Atoms in white are hydrogen, grey are carbon (you’ll notice this is most of them). The single red atom is the oxygen.
Three dimensional model of a cholesterol molecule

Three dimensional model of a cholesterol molecule

Like any fat, cholesterol is bad for us if we have too much of it. Cholesterol is recognised as being especially good at promoting the build up of fatty deposits in our blood vessels (see the ‘atherosclerotic plaque’ below). This leads to the vessels becoming clogged up with debris and ultimately a heart attack. Listen to someone who knows a lot more than me talk more about the dangers of having a high cholesterol level here.

So how much cholesterol should I eat?  My advice is to not worry about cholesterol specifically, but simply try to eat a sensible balanced diet. It’s certainly not wise to obsess about eating foods which are ‘low in cholesterol” at the cost of ignoring other dietary issues. This would be a shame as most of the cholesterol in our bodies in synthesised automatically from simpler fats. That means even if you consume zero cholesterol but a reasonable amount of other fats, it’s still quite possible to have a high blood cholesterol level.

Still want to eat chips?

'Atherosclerotic plaque' Still want to eat chips?

To move on to something less stomach turning than blood clots and dietry advice from a bingeing student, let’s now focus on the truth about some of the quite amazing positive things that cholesterol does for our bodies.

Cholesterol plays an important role in controlling the fluidity of our cell membranes. It sits between the phospholipids – the slippery molecules which make up our cell membranes – at random intervals and controls how easily they can slide past each other.

CellMembraneDrawingA cartoon of a fluid-like cell membrane. Spot the phospholipids and cholesterol. 

 

The cell membrane is vitally important for ensuring the right kinds of chemicals can get in and out of our cells. It’s even more important in nerve cells. With life giving nerve impulses whizzing along the neurones, the cell membrane is crucial in insulating the electrical impulses. cholesterol has been shown to form complicated 3D structures within the membrane to beef it up and prevent the electrical impulses leaking out.

So there you go. No need to be scared of cholesterol anymore. If you were.

 

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