"Make straight the path..."

I find cyclical processes hard to understand. Maybe it's because I grew up in the age of digital clocks.

When I see a cycle, I like to draw it out as a linear sequence. For example, here is Figure 17.18, linearized to show the steps involved in adding one amino acid to a polypeptide chain. Comparing the top and bottom cartoons, you can see that the end is the same as the beginning. But shown this way, it is easier for me to think of a "beginning" and an "end." Click to enlarge...

By the way, happy new Year!

Speaking of microcosms...

... everybody has a little trouble comprehending the relative sizes of things that are either very very big, or very very small. To better appreciate the relative sizes of very small things, you can zoom in here (thanks to the Genetics Department at the University of Utah).

Use the scroll bar at bottom to zoom. First you see the embryos of three different plants (coffee, rice, sesame). From this millimeter size range, you can zoom all the way down to a carbon atom (320 picometers in girth). Along the way, see a couple of biggish protozoans, a variety of human cells, and a single human chromosome; then you zoom past a baker's yeast and a bacterium. You see a mitochondrion, which is another sort of bacterium. The "coated vesicle" is what gets pinched in from the plasma membrane during endocytosis; it is about the same size as the HIV virus particle. The smallest virus shown, Rhinovirus, causes the common cold. It does not have a lipid envelope, but is just a package of RNA in a protein coat. It is about the same size as a ribosome.

Light Reactions of photosynthesis: new cleaned-up coloring page!

I finally found a few minutes to clean up (and slightly improve) my diagram of the "Light Reactions" of photosynthesis: now it is a proper coloring page, ready to print and color.
 Here it is (click to enlarge, ctrl-click or right-click to save...)

The improvement was to add, at bottom, an icon for the Calvin cycle (the "Dark Reactions"), showing how the Light Reactions supply the necessary ATP and NADPH. The Calvin cycle is, after all, the whole point. It's how plants get ALL their carbon. It's where all our food comes from! To build sugar out of carbon dioxide takes CHEMICAL ENERGY (ATP) and REDUCING POWER (NADPH).

Here is a colored version:

I know it looks bewildering at first, but it may be helpful. Questions? Ask!
Cheers,
Morgan G.

Speaking of time-lapse cinematography…

I highly recommend the movie "Microcosmos: the people of the grass."

This almost wordless 1996 flick shows us the lives of critters that are small enough to move around between blades of grass, as we might walk among the trees in a forest.

Further, the filmmakers show us events in the meadow-forest that happen too quickly or too slowly for human perception - respectively by slowing down or speeding up the playback of the film.

I thought of this as I was reading to my son from T.H. White's novel The Sword in the Stone: for the benefit of his pupil, the not-yet-King Arthur, Merlyn uses his magic to speed up time, so the young Arthur can evesdrop on the conversations of trees (he must listen at half a year per second, or 15 million-fold time compression), or on those of rocks (listening at two million years per second).

The makers of "Microcosmos" also use a remote-controlled helicopter, with a tiny high-resolution videocamera, to follow a dragonfly in its flight.

It's an utterly beautiful movie. If you've never seen it, or saw it only as a small child (it was released in 1996) you really should find yourself an uninterrupted 80 minutes to take it in. You can get it streamed on Netflix.