We know that lipids are stored in the form of triglycerides. They store twice the amount of energy than in sugars (fats: 38 kJ/g; glycogen: 17 kJ/g).

To illustrate the importance of fats as energy storage molecule, an imaginary scenario was given (adapted from Berg et al. 2002).

A person that weights 70 kg has 15 kg fat in average (assuming 20% fat content). It seems to be a horrible amount to shake off for girls and bodybuilders.

But what if fats are fully replaced by glycogen, the storage molecule for sugars? Well, glycogen has only half the amount of energy as in fats. To achieve the same amount of energy storage, 30 kg (*15 kg x 2) of glycogen is needed.

That is not the end of the story.

Glycogen has many polar hydroxyl groups. So for every gram of glycogen, it attracts and binds to 2 grams of water molecules.

Consequently, 30 kg of glycogen will bind to 60 kg of water.

In conclusion, if we were to fully replace fats with glycogen, we need to put on 90 kg of glycogen and water! We should be thankful. Because of fats, we are not fat.

Today I was talking about the structure of DNA.

In one part, we were looking at the X-ray diffraction pattern of DNA double helix.

With reference to this webpage, I decided to run a live simulation to mimic what was done by Rosalind Franklin.

It was very simple. I illumined the spring coil (took from a pen) with a laser pointer and pointed it to the screen about 5-7 m away.

A student volunteered to become my scientific assistant and shot the picture below!

Immediately, this picture was sent by Whatsapp and each student can look at the image simultaneously.

It was cool and the students liked it very much. More importantly, this is going to leave a deep impression in their minds and stimulate their interest in biochemistry.

Above is the original image obtained by Franklin and Wilkins for comparison.