Turning a molecular wheel with a flow of protons

(image source)

A scientist's story of first hearing Peter Mitchell's proposal that a concentration gradient of protons was the energy source for ATP synthase. 

I recommend reading this starting in the middle, with "In 1955..." (highlighted, second sentence of the 3rd paragraph) and then looping back to the beginning of the article afterwards.

"I remember thinking... that I would bet anything that ATP synthesis didn’t work that way."

Mitchell was an unusual scientist:

"For much of his career he worked in his own lab in a... house... his research funded in part by a herd of dairy cows." (source)

In this video, see how ATP synthase works with key molecular details gained in part from solving protein structures in different states (ATP-bound, ADP-bound states etc) mostly from John Walker's lab in Cambridge, England. Walker shared the Nobel Prize for deciphering the structure of ATP synthase.

 

* EVERYTHING ABOVE WAS POSTED AFTER THE 1ST EXAM *

.

Sickle cell anemia

Learn more about sickle cell anemia, the most common inherited blood disorder in the US, at an NIH web site or the Sickle Cell Disease Association of America web site.

Here's a NY Times story about recently approved gene therapy (for those interested in science writing, the author Gina Kolata is a great writer who tells engaging stories while reliably getting the science right, and she has several books out). Gene therapy is an important step forward, but sadly, as this story covers, the current cost of gene therapy makes it unavailable to many patients, and as these stories cover, gene therapy patients have faced some challenges to date.

Here's an earlier 22-minute radio story about the first US patient whose bone marrow cells' genes were edited using CRISPR. 

Get an idea of what else is being tried right now toward cures and toward treatments for symptoms by seeing current clinical trials.

Brownian motion simulation

Try out this simulator to get an intuitive sense for how Brownian motion works. Slide the "energy" slider to the right to see what happens at higher temperatures. And be sure to "drag to see what's actually going on". Much of the theory here was worked out by Einstein. Here's a translated version of Einstein's original 1905 publication that began to explain what causes Brownian motion.

Dorothy Crowfoot Hodgkin

Read about Dorothy Crowfoot Hodgkin here, on Wikipedia, and in her biography.

(Image: British postage stamp honoring Hodgkin)

At the beginning of the course, I explained that the science we are discussing intersects with other aspects of life in many ways, and that I'd discuss those ways on occasion. For anyone interested in how women have been portrayed in science journalism, here's a headline from when Hodgkin won the Nobel Prize, and another, plus a newer checklist developed to help science journalists think clearly about whether their writing rehashes cliches at the expense of explaining the science and the scientist's achievements. Here you can read a little detail about the exclusion of women in research discussions in the time and place where Hodgkin was making discoveries. 

How many diseases are linked to specific genes? How many disease genes are there?

(image credit)

Check back on the links below and watch the numbers go up throughout the course!

• How many diseases have genes associated with their malfunctions? Here is a periodically-updated list. As of 15 years ago (Jan 27, 2011), 2949 diseases were known with "Phenotype description, molecular basis known: Total". Today (Jan 26, 2026) it's 7091 diseases – an average increase of nearly a new one discovered per day!
• How many disease genes are there? See "Total number of genes with phenotype-causing mutation" here. As of today (Jan 26, 2026) it's 5045 genes.  

Identifying a gene associated with a disease can be a big step toward developing both diagnostics and treatments. What kinds of genes are being discovered now? HERE is a link to news stories on some discoveries made recently. HERE's how they're discovered.

The earliest snowflake images

In 1885, Vermont farmer Wilson Bentley attached a camera to a microscope and became the first person to successfully photograph an individual snowflake crystal.

"...it was my mother who made it possible for me, at fifteen, to begin the work to which I have devoted my life. She had a small microscope which she had used in her school teaching. When the other boys of my age were playing with popguns and slingshots, I was absorbed in studying things under this microscope: drops of water, tiny fragments of stone, a feather dropped from a bird's wing, a delicately veined petal from some flower. But always, from the very beginning, it was the snowflakes that fascinated me most." -from a 1925 interview with Bentley

Henrietta Lacks

Learn more about Henrietta Lacks at her Wikipedia page. Below, historian and filmmaker Henry Louis Gates talks about Henrietta Lacks and the history of medical consent and race.

About the book about Lacks that I mentioned in class: "...the science end of this story is enough to blow one's mind... But what's truly remarkable... is that we also get the rest of the story, the part that could have easily remained hidden had she not spent ten years unearthing it: Who was Henrietta Lacks? How did she live? How she did die? Did her family know that she'd become, in some sense, immortal, and how did that affect them?" -Jad Abumrad, Radiolab

There's a movie too.

Images from microscopes day

Our images from microscope day!

Amazing images from microscopes

The Nikon Small World web site has some stunning images and videos.

Image: Growing tip of a red algae by UNC's own Dr. Nat Prunet. Go Heels! See this and other images from UNC here.

Breaking the resolution limit of light microscopy

image credit: HHMI

Here's a photo of the original PALM microscope in the living room where it was developed, and a story about this and related technologies. The Wikipedia page on super-resolution microscopy discusses PALM and several other tricks for breaking the limit of resolution for light microscopy, and this article is a nice description of the challenges and multiple clever solutions to improving resolution beyond the usual limit.

source

"...that’s where we learned about photoactivatable fluorescent proteins.... it became obvious to Harald and me that this was the missing link for the idea that I had pitched after I left Bell: we could isolate a few molecules at a time by activating limited subsets of photoactivatable proteins. It seemed so easy."

"...We were both unemployed, but Harald had some of his equipment from Bell [Labs]..."

-from Betzig's Nobel speech

Xiaowei Zhuang's lab developed a similar method, called STORM, around the same time as PALM was developed. See "STORM image gallery" at her lab web site for some super-resolution images. 

 

Struggling with your grades? Fear not!

Watch the 45 seconds between 1:45 and 2:30 to see how Chemistry Nobel Laureate Marty Chalfie (of Green Fluorescent Protein fame) did in Chemistry classes in college.

Louis Pasteur and his home

Louis Pasteur's old house is now a museum, currently under renovation through 2028. You can see it well documented here. Pasteur is buried in the basement, in an elaborate crypt (pictured here). 

Microns, nanometers, etc.

Powers of Ten, a classic Charles & Ray-Bernice Eames film on grasping the sizes of things from human scale out to the then-known universe, and back in to subatomic particles.

More images from Robert Hooke's Micrographia

Here's the whole book.

Hooke's book begins with an apology to the King of England, for, well, discovering things.

Hooke's methods for immobilizing some of the insects were creative:

...I gave it a Gill of Brandy, or Spirit of Wine, which after a while e'en knock'd him down dead drunk, so that he became moveless...

Hooke's engraving of a head of a hoverfly, from Micrographia

My favorite of van Leeuwenhoek's letters, with a surprise ending

"Concerning the Worms in Sheeps Livers, Gnats, and Animalcula in the Excrements of Frogs" (van Leeuwenhoek, 1700)

In this letter, he describes finding microscopic life in frog poop. I especially like the surprise ending in the last 3 paragraphs – starting, "On the fifth day the Frog had dung'd again...." on the bottom of page 517. Scientific papers never end like this.

Google on van Leeuwenhoek's 384th birthday

A popular book about cell biology

A great, vivid exploration of some fascinating topics in cell biology. See the "Read sample" button on the left side of this page to read parts of the book now. Also available as an audiobook.