Light reading for today

[rebeccmeister]

Today I am reading a review paper on the function and regulation of the insect fat body. If you've never heard of the insect fat body before, well. It doesn't really have a direct parallel in vertebrate animals, and that's probably why. However, it shares much in common with the human liver, in terms of its function. It helps to synthesize insect energy reserves in the form of fat and glycogen, and is involved in synthesizing most of the proteins and metabolites that appear in the circulating insect hemolymph. If you somehow schlurped out the entire fat body, an insect would die, quickly.

There's another new thing to consider - bug juices. Insects don't have blood in the same sense that vertebrates do. Instead, they have a blood-like fluid, so it's called "hemolymph" (hemo- for blood, -lymph for fluid). Just - no red blood cells. In lieu of a closed circulatory system, where all of the fluid is channeled throughout the body in a set of pipes (veins, arteries), insects have an open circulatory system. Various factors encourage the hemolymph to move around, including a heart-like "aortic arch," and the net result seems to work fairly well, to judge by the fact that over half of the species on earth are insects.

Anyway. Lots of biochemistry in today's reading, so I'm drawing tons of cartoons to keep myself moving through the material. I have sat through and fallen asleep through countless, countless talks covering many different aspects of biochemistry. If you put me in a seat in a darkened room and start showing pictures of biochemical pathways, I'll be out cold in two minutes flat. I'm thinking I should keep a biochemistry textbook next to my bed for times when insomnia strike. Is this due to poor presentation skills, or something wrong with my ability to focus? Who knows.

But if I can just get myself to draw out cartoons, I can learn about stuff like this**, and it's fascinating.


**Edited to add: I am pulling this link because I am now convinced it was a link to a website specializing in intellectual theft, and while I may not agree with traditional publishing practices, I think authors deserve credit for their intellectual work, and the referenced piece clearly required a lot of work. Here is the original book. I wish the author and publisher the best in handling this intellectual property theft.

Why do I know it's theft and something is wrong with it? There were no methods to track down the (extensive) citations within the text, and there was no acknowledgement of the author.

Comments

[rebeccmeister.livejournal.com]

I like biochem, too, I just can't focus on it for too long or listen to someone else talk about it. Learning about lipid utilization has been fascinating!

I also think there are a lot of cases where things just aren't explained especially well.

It's interesting to think about what happens when an insect goes from non-flight to flight - major metabolic changes happen, and they differ from how humans mobilize energy for exercise.

[randomdreams.livejournal.com]

So what do insects do? I know we use muscle glycogen until it's exhausted, and then use liver glycogen cycled through the blood.

[rebeccmeister.livejournal.com]

Oh, it's interesting. They use trehalose, which is a glucose disaccharide, as their mobilized form of glycogen (glycogen tending to be a large, bulky storage polymer). I think we have to convert liver glycogen to glucose for transport through the bloodstream.

Insects are also better at using fat than we are - insect flight is predominantly fueled by trigylcerides (triacylglycerol), which is converted to diacylglycerol in the insect fat body, and popped into lipoproteins for transport (because they're nonpolar and hemolymph is polar). The lipoproteins are transported to muscle, where the diacylglycerol is popped out and converted to free fatty acids.

The interesting piece is that we also have high-density lipoproteins and low-density lipoproteins, but ours are used for different purposes (I'm not as familiar with what, since I've focused on the insect story so far).

[randomdreams.livejournal.com]

Interesting. Yeah, we seem to use the lactate shuttle pathway to get glucose-ish material from the liver to the muscles during fairly heavy exercise, although I seem to remember that lactate levels also trigger some sort of lipid metabolic response in mammals.