BTS001 – Cholesterol and lipoproteins basics

The blogpost covers the design process of an illustration used in the blogpost “Cholesterol and ‘cholesterol’“.

The design of cholesterol and lipoproteins

I have done quite a bit of research to design these images. I wanted to make a clear distinction between the cholesterol molecule and lipoprotein particles. Lipoprotein particles also needed to be distinct from one another. I looked into the biochemical differences of these molecules and particles for their design.

what is cholesterol
Overview of cholesterol and lipoproteins

Designing the cholesterol molecule

Designing the schematic depiction of a cholesterol molecule was fairly straight-forward. For biochemical molecules I like to reference their chemical structure. The structure is often interesting and distinct from other compounds. In the case of cholesterol, I used the shape of the three 6-carbon rings and the 5-carbon ring.

I pick colors based on the complexity of the story, how many elements I require for a proper explanation and how these elements are related to each other. The orange color of cholesterol is reused for other elements, but not always as dark or saturated.
I also like to link my illustrations together by reusing colors for the same biological concepts or molecules.

Designing lipoproteins

Lipoproteins are categorized based on their size, density, and composition. Composition is further subdivided into the content of the lipoprotein and their coating. I have used several of these characteristics in my depiction of lipoproteins.

  • Size should be self-explanatory. The proportions are not correct, of course, but I did try to show the relative differences in lipoprotein size.
  • The difference in density is shown by the brightness of the colors. The darker the colors, the denser the lipoprotein generally is. HDL has the highest density and darkest colors, but chylomicrons are very buoyant and therefore their colors are fainter.
  • The content of the lipoproteins is shown using a pie graph of the relative amounts of cholesterol, triglycerides (fats) and other compounds. I got this information from Boron & Boulpaep, Medical Physiology, 2nd edition (one of my study books). Using the pie graphs, the transition from VLDL > IDL > LDL becomes very clear.
  • Lipoproteins are also differentiated based on their coating. But since making that distinction did not help with the clarity of my blogposts, I decided to leave it out.

The colors of the lipoproteins are based on the pallet I have used in previous illustrations. Carbohydrates are blue-purple, proteins are blue-green, and fats are orange-yellow. It’s not always useful to stick rigidly to this format, so I change it when it is beneficial to the message.
Because fats are yellow and cholesterol is orange-red, I used a blue color for other, less-important elements of the illustrations.
The liver has a dark-red color, which is its natural color. I find that the shape of the liver by itself is not distinct enough for most people to recognize it right away.

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