Without the chemistry of photosynthesis, ozone, and a molecule called Rubisco, none of us would be here. So how did we get so lucky? To find out, host David Pogue investigates the surprising molecules that allowed life on Earth to begin, and ultimately thrive. Along the way, he finds out what we’re all made of—literally. (Enjoy this program with Audio Description.)
Beyond the Elements: Life
PBS Airdate: February 17, 2021
DAVID POGUE (Science and Technology Author): What’s it take to make our modern world?
I’m David Pogue. Join me on a high-speed chase through the elements and beyond.
Oh, my god.
As we smash our way into the materials, molecules and reactions…
AMANDA CAVANAGH (University Of Illinois, Realizing Increased Photosynthetic Efficiency [RIPE)]): It’s a really cool enzyme, because it makes life on Earth possible.
DAVID POGUE: …that make the places we live, the bodies we live in and the stuff we can’t seem to live without.
The only thing between me and certain death is chemistry? From killer snails…
MANDË HOLFORD (Hunter College): Just when you think you’ve heard of everything, nature will surprise you.
DAVID POGUE: …and exploding glass to the price a pepper-eating Pogue pays…
There’s got to be some easier way to learn about molecules.
…we’ll dig into the surprising way different elements combine together and blow apart.
In this hour, we tackle one of the biggest mysteries of all: the origin of life.
JACK SZOSTAK (Massachusetts General Hospital/Nobel Laureate): How do a bunch of chemicals get together and start acting like a cell?
DAVID POGUE: Part of the answer might be soap?
We explore how the chemistry of life transformed the planet…
LISA AINSWORTH (United States Department of Agriculture, Agricultural Research Service Scientist, University of Illinois): So, everything that we eat, the air that we breathe, all have to do with the process of photosynthesis.
DAVID POGUE: All right, so let’s find the lipids aisle.
…I go shopping for the macromolecules of my body…
You’re telling me that that’s only half the amount of fats in my body?
MONICA HALL-PORTER (University Of Texas, Austin): Absolutely.
DAVID POGUE: …and I meet an engineer who uses nature’s tools to invent new molecules.
FRANCES ARNOLD (California Institute of Technology/Nobel Laureate): Humans have been using microbes to make beer and wine. Instead of making sake, we make jet fuel.
DAVID POGUE: It’s Beyond the Elements: Life, right now, on NOVA.
The world we live in is made of atoms, all listed here as elements on the Periodic Table. They’re the building blocks of everything around us. And putting atoms together to make molecules and compounds is what we call “chemistry.”
And maybe the strangest event in the history of chemistry is the birth of biology. How do a bunch of chemicals somehow get together to form life? And if you look back at the conditions on early Earth, how did life get off the starting block?
There was a turning point, the evolution of a transformative series of chemical reactions that, over time, remade the planet, even allowing us to come along.
But first, let’s take a trip back to Life 1.0.
So here’s the ad: “Planet available, recently scoured by asteroids. New construction. Now with many water views. The atmosphere? A fixer-upper, devoid of oxygen. Likely full of whatever the volcanoes spewed forth, gases like hydrogen sulfide, and methane.”
Somehow, in that very harsh environment, primitive life got its start. But the going stayed tough. Food, molecules and minerals that early organisms could use for energy, consisted of whatever was left over from Earth’s formation or was welling up from the earth’s core, at places like deep sea vents. But in a surprisingly short amount of time, perhaps 500-million years, a new survival strategy evolved, possibly the most important chemical process for life on Earth today: “photosynthesis,” the ability to turn sunlight into fuel.
Life now had access to the vast power of the sun. In the words of one biologist, “When photosynthesis entered the picture, life connected up to the cosmos.”
LISA AINSWORTH: So, everything that we eat, what we wear, the air that we breathe, the ecosystem services that we rely on, so, things like having clean water, all have to do with the process of photosynthesis. So, it’s an incredibly important, probably the most important process on the planet.
DAVID POGUE: Photosynthesis harnesses the power of sunlight to break down water molecules. Discarding the oxygen, it uses the electrons from the hydrogen atoms to power the assembly of carbon dioxide molecules into carbohydrates, which become both building blocks and long-term energy storage.
DONALD ORT (University Of Illinois, Realizing Increased Photosynthetic Efficiency [RIPE)]): It’s not an overstatement to say that all life on this planet depends on photosynthesis.
STEVE LONG (University Of Illinois, Realizing Increased Photosynthetic Efficiency [RIPE)]): It’s exactly where all of our food comes from, directly or indirectly. So, understanding how this process works is so important to humanity.
DAVID POGUE: Steve Long and Don Ort, two plant biologists at the University of Illinois at Urbana-Champaign, along with thousands of other scientists, from around the world, have spent decades teasing apart the workings of photosynthesis.
DON ORT: Light intensity is 900, right now?
STUDENT: Right now, yeah.
CARL BERNACCHI: Oh, yeah. That makes sense.
DAVID POGUE: Now, with that knowledge in hand, there is a new international research effort, based here at the university, with an audacious goal. The program’s called RIPE: Realizing Increased Photosynthetic Efficiency.
AMANDA CAVANAUGH: This year was a huge hit for the canola farmers, because it was too wet.
STEVE LONG: So, I’ve been wondering whether it would be worth trying to find a substitute as our testbed.
DON ORT: That’d be perfect.
DAVID POGUE: These folks want to hack photosynthesis.
But why would you want to do that? Because experts think the earth is about to get a whole lot more people. Today, the world’s population is close to eight-billion, and that’s forecast to hit 9.7-billion by 2050, raising the question: will there be enough food?
STEVE LONG: If you look at the current rate at which we are improving crop productivity per acre of land, we are not going to get there.
DON ORT: Part of the answer is going to be redesigning photosynthesis.
DAVID POGUE: To learn more about RIPE’s plans, I’ve joined Lisa Ainsworth, a U.S.D.A. scientist and professor at the University of Illinois…
LISA AINSWORTH: You can see just how different the height is.
DAVID POGUE: Wow.
….on an early morning tour of a field that contains 600 different varieties of soybeans.
Usually, you hear about efficiency, like of a gas engine, measured in terms of percentage, how much fuel is ultimately converted to energy. What’s the percentage efficiency for a plant?
LISA AINSWORTH: Well, in terms of how much of the light energy it turns into sugar, it’s pretty low, maybe around three percent.
DAVID POGUE: Three percent? That’s terrible. But you guys are going to help it?
LISA AINSWORTH: That’s the plan.
DAVID POGUE: To improve photosynthesis, two other researchers with RIPE, Amanda Cavanagh and Paul South, have focused on one of its key molecules. It has a very catchy name.
AMANDA CAVANAGH: So, the molecule is what we biologists call an enzyme. And so, it does the work. Enzymes are like biological workers. And the enzyme’s called “RUBISCO.”
PAUL SOUTH (Louisiana State University, Realizing Increased Photosynthetic Efficiency [RIPE)]): It’s R.U.B.P., or “ribulose bisphosphate carboxylase oxygenase.”
AMANDA CAVANAGH: And it’s, for most plant biologists, one of our favorite enzymes on the planet.
PAUL SOUTH: Yeah, rubisco is our shortened term for it.
DAVID POGUE: Mainly because it’s fun to say?
AMANDA CAVANAGH: Well, it’s super fun to say.
DAVID POGUE: Rubisco.
AMANDA CAVANAGH: Of course, rubisco. But, it is also a really cool enzyme, because it makes life on Earth possible.
DAVID POGUE: Rubisco may not look so special, but it is arguably the most important enzyme on the planet, because of its critical role in photosynthesis. Rubisco’s job is to grab a molecule of carbon dioxide and feed it into a molecular machine that’s building carbon chains.
That means, any carbon atom that’s part of any plant, anywhere, got there thanks to rubisco or one of its close variants. And because we eat plants or animals that ate plants, that also includes just about every carbon atom in your body. All approximately eight-hundred-million-billion-billion of them. That’s 26 zeroes.
Not bad rubisco, not bad.
PAUL SOUTH: Yeah, so if it’s ever come from a plant, it had to have gone through that enzyme of rubisco.
DAVID POGUE: That’s wild. How come there’s not a memorial to rubisco in Washington? It seems like, sort of important.
Rubisco is important, and that’s why it’s the most plentiful protein on Earth. But just because you’re important, doesn’t mean you’re entirely competent.
PAUL SOUTH: It’s, in this case, not the best enzyme in the world.
AMANDA CAVANAGH: It’s got a hard job, so it’s doing its best, but at the same time it exists in an atmosphere that’s not predominantly carbon dioxide, it’s mostly oxygen.
PAUL SOUTH: And about one in every four or five reactions, it grabs oxygen instead of carbon dioxide.
DAVID POGUE: That’s right. Rubisco screws up about a fifth of the time. Instead of attaching a carbon dioxide, it attaches an oxygen molecule, and that’s trouble.
You’re saying nature has created a screwed-up little worker enzyme?
PAUL SOUTH: Yeah. So 400-million years ago, when this enzyme evolved, there wasn’t very much oxygen in the air.
DAVID POGUE: All right. So, I’m the little rubisco enzyme and, like, on the conveyor belt, here. And like carbon dioxide, carbon dioxide, carbon dioxide, carbon dioxide, oxygen. And I, I don’t notice I accidentally grabbed oxygen out of the box.
PAUL SOUTH: And it produces compounds that are inhibitory to photosynthesis. So, it kind of starts to shut things down.
DAVID POGUE: I mean it’s been going on for billions of years and nobody has cared.
AMANDA CAVANAGH: Yeah, well.
DAVID POGUE: I mean, it all basically works.
AMANDA CAVANAGH: Photosynthesis, right now, is sort of a victim of its own success. Rubisco certainly is. So, by oxygenating the atmosphere via photosynthesis, you now have a huge amount of oxygen in the atmosphere, but you need a carbon dioxide to make the reaction work.
DAVID POGUE: So, what happens when rubisco screws up? The result gets shipped out through a couple other parts of the cell to where the mess is taken apart and recycled, all of which consumes a lot of energy.
So, if you could fix this inefficiency problem, the plant might make more soybeans, corn, whatever it is?
AMANDA CAVANAGH: That’s exactly it. Then they will have that energy to put towards something that we will consider useful, like making more food for us to eat.
DAVID POGUE: Is this just a crazy theory or is there some indication that this could actually work?
AMANDA CAVANAGH: There is quite a bit of evidence that this is working. So, right now, we have this tested in a couple of model species.
DAVID POGUE: It is tropical in here.
Amanda and Paul take me to the greenhouse to see one example. Using two genes, one from algae and the other from a pumpkin, they’ve modified tobacco plants to address rubisco’s “sloppy work.”
And why are we using tobacco plants?
AMANDA CAVANAGH: Yeah, tobacco’s a really useful model crop for us.
DAVID POGUE: Why tobacco? Turns out, it’s one of the easiest plants to genetically manipulate, which makes it a common test subject.
PAUL SOUTH: They have definitely shown improvements in plant growth and total biomass. And we’ve been studying the rates of photosynthesis, and we are pretty confident, now, that our model crop is successful in this pathway. And now we’re really interested in moving these into something we like to eat.
DAVID POGUE: Reducing the energy penalty crops pay for rubisco’s mistakes could be huge. In soybeans, a 25 percent reduction could result in plants that produce more than 60-million more bushels a year.
AMANDA CAVANAGH: This, to a lot of people, is an idea that might be out there. But if we can get it, if we can get this moonshot approach to work, then we’re going to have more food. And so that’s really what drives what I do.
DAVID POGUE: The RIPE program is international. And likely, so will be the reach of any of its discoveries. But work like theirs is not without controversy. Some of RIPE’s solutions depend on crossbreeding plants, chosen for their genes; but other solutions, like the rubisco work, depend on genetic engineering, also called genetic modification or G.M., adding new genes from other types of plants, or even organisms, entirely.
The laws governing genetically modified crops vary from country to country, especially when it comes to labeling their use in food, and there have been objections to some companies that patent their new crops and control who can plant them. But the general scientific consensus is that they are no more dangerous than conventional crops, though they need to be carefully studied for potential health and environmental effects.
The U.S., unlike Europe, has largely adopted G.M. plants. An overwhelming percentage of corn, soybeans and cotton grown in the United States is genetically modified.
STEVE LONG: I understand there are concerns. As a scientist, I feel those concerns have very little validity, although clearly people have become very concerned, particularly in Europe. Of course, in this part of the world, genetically modified crops have been grown for over 20 years. This technology has spread throughout the Americas.
DAVID POGUE: In fact, as the global population grows, it’s in poorer countries that RIPE’s work may end up having the greatest impact, especially if genetically modified foods gain acceptance.
STEVE LONG: The place where I see the technology needed most is actually in sub-Saharan Africa. And this opposition to G.M. is having quite an influence in Africa. It’s keeping the science, which is needed, out. And I fear that this could risk people starving when we could actually be giving them seed which would allow them to feed themselves into the future.
DAVID POGUE: Even if scientists succeed in improving photosynthesis, it won’t have anywhere near the dramatic impact of the original version introduced about three-billion years ago. Back then, scientists believe, photosynthetic cyanobacteria began cranking out oxygen as a waste product. Eventually, bacteria produced enough oxygen that it started to accumulate in the atmosphere, which, in turn, gave rise to one of life’s underappreciated molecular allies, the ozone layer.
It’s in the lowest level of the stratosphere, between, roughly, eight and 22 miles up. Atmospheric research planes venture up here but not much else. The ozone comes from a process even higher up in the stratosphere. There, solar radiation busts up O2 molecules into individual oxygen atoms. They drift down to the ozone layer, where they convert O2 into O3, ozone.
Despite the name, there’s not that much ozone in the ozone layer, less than 10 parts per million, yet it’s had a profound effect on the evolution of life on Earth.
To find out more…
So, ozone is O3, right?
KERRY HANSON (University of California, Riverside): Ozone is O3.
DAVID POGUE: …I travel to the University of California, Riverside, to meet Kerry Hanson…
KERRY HANSON: We came alive because…
DAVID POGUE: …a research chemist who studies how molecules like ozone and those in sunscreens interact with light.
KERRY HANSON: Any molecule can absorb light.
DAVID POGUE: It turns out the ozone layer and sunscreens have a lot in common. This O3 gas is out there in the atmosphere in such quantity that there’s an envelope around the whole planet?
KERRY HANSON: Yeah. It’s a layer. Think of, like, a sunscreen, you know, how we use sunscreen on our skin?
DAVID POGUE: Yeah.
KERRY HANSON: It’s the exact the same thing. The ozone layer is Earth’s sunscreen.
DAVID POGUE: Both the ozone layer and sunscreens protect us from the harmful effects of ultraviolet radiation or U.V., a kind of sunlight that, unlike the colors of the rainbow, we can’t see. On the electromagnetic spectrum, visible light sits here, but U.V. sits up here, at a higher energy.
Scientists divide it roughly into three kinds, A, B and C. And while A and B aren’t good for you, and they’re the reason to wear sunscreen, it’s C that’s the big problem for living things. Because it’s particularly destructive to D.N.A. Kerry tells me how all this relates to ozone.
Just another Sunday, and it’s kind of like volleyball…
KERRY HANSON: Oh, he’s good.
DAVID POGUE: …well, if the balls were different kinds of U.V.
In the early days of life on Earth, before photosynthetic bacteria oxygenated our atmosphere…
Get it, get it, get it! Yeah, yeah, yeah!
…there was no ozone layer and no global defense against ultra violet radiation.
The most dangerous kind, U.V.C., bathed the planet, which may have effectively limited where life could grow. But oxygen accumulating in the atmosphere and the rise of the ozone layer changed all that. The layer blocks all the U.V.C. and most of the U.V.B. from reaching the earth’s surface.
KERRY HANSON: Oh, good block.
DAVID POGUE: Here’s how it works: when U.V. radiation hits a molecule of ozone, it splits it into an oxygen atom and a molecule of O2; the U.V. light has been absorbed and neutralized; the lone atom quickly rejoins another molecule of O2, to reform ozone. The net result is a conversion of that harmful radiation into heat. Despite the ozone layer, we can still get hit by unhealthy amounts of U.V. And that’s why it is a good idea to use sunscreen.
KERRY HANSON: If you read the label and if it says broad spectrum, that means it’s blocking U.V.B. and U.V.A.
DAVID POGUE: Wow.
KERRY HANSON: Not U.V.C., like ozone, but U.V.A. and B.
DAVID POGUE: Just like we use sunscreen to block harmful U.V.A. and B radiation from our skin, the ozone layer protects planet Earth from harmful U.V.C. radiation that would destroy the building blocks of life, D.N.A.
KERRY HANSON: Without the blocking of U.V.C. by the ozone layer, life would not have been able to come out of those oceans, come up onto land, and you and I wouldn’t be talking here today.
DAVID POGUE: Thanks, ozone!
Without that global protection, the grand story of evolution that began from single-cell ocean-dwelling life and led to the wondrous complexity of multicellular animals occupying land, sea and sky would probably never have been told.
And yada yada yada.
Yeah, yeah. I know, the evolution of life is important, but let’s talk about something really important: me; or, at least, me and my molecules.
I know what elements I’m made of: C.H.N.O.P.S.: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. C.H.N.O.P.S. There are other elements in the human body, but these are the main six. And, of course, a good chunk of me, by mass, is good old H2O.
But if you take that water away, most of what’s left is macromolecules, mostly big, long polymers,chains of smaller molecules.
Yeah, so I once went “chnopping.” That’s C, H, N, O, P, S.
To learn more about them, biologist Monica Hall-Porter, formerly at Lasell University, now at the University of Texas, offers to show me around a local…supermarket?
It’s kind of weird. I ask you about the molecules of my body and you bring us to a grocery store.
MONICA HALL-PORTER: Yeah, so today’s shopping trip is about the macromolecules that actually make up the human body: specifically protein, lipids or fats, carbohydrates and nucleic acids. And if you take a look around the grocery store, there are many examples of those macromolecules here.
DAVID POGUE: All right, show me the ropes.
MONICA HALL-PORTER: Let’s go shopping.
DAVID POGUE: Our first objective? Protein molecules.
Monica tells me, by weight, that’s about 20 percent of my body.
Does that mean pure masculine muscle? Is that what you’re saying?
MONICA HALL-PORTER: Well, not necessarily muscle. Proteins are the molecules that actually do work in cells, so, not just composing muscle, but also the proteins that serve as the structural proteins in our hair and our fingernails.
DAVID POGUE: The most abundant protein in your body is collagen, making up fibrous tissues like skin, tendons and ligaments. There’s also collagen in teeth and bone.
But even though there are tens of thousands of different proteins in the human body, maybe millions—no one is sure, amazingly—they’re all made from stringing together about 20 different kinds of small molecules called “amino acids,” which we get by breaking down the proteins we eat in a variety of foods.
MONICA HALL-PORTER: And so, when we consume protein, like in turkey for example…
DAVID POGUE: Whoa.
MONICA HALL-PORTER: …our body breaks the amino acids down, and then the amino acids are incorporated into proteins that our body synthesizes or makes.
Yep, there you go.
DAVID POGUE: Handsome little gobbler. Next on the macromolecule shopping list, lipids.
All right let’s find the lipids aisle.
MONICA HALL-PORTER: There is no lipids aisle, but we can get oils and fats. So, let’s head down this way.
DAVID POGUE: All right.
MONICA HALL-PORTER: And let’s get some oil.
DAVID POGUE: This is massive. How much fats are we getting?
MONICA HALL-PORTER: A lot.
DAVID POGUE: Oh, man. This seems like we’ve got 15 pounds of fats here. And you’re telling me that’s only half the amount in my body?
MONICA HALL-PORTER: Absolutely; you’re about 30 pounds of fat.
DAVID POGUE: Now, I have to say I find that a little insulting.
MONICA HALL-PORTER: Well, you shouldn’t.
DAVID POGUE: Compared to proteins, lipids, or fats, do get a bad rap. But in addition to their role in cell membranes and long-term energy storage, you know, body fat, they also provide protection for internal organs.
Oh, and don’t forget the lipids in earwax.
MONICA HALL-PORTER: And so, literally, there’s fat in every part of you.
DAVID POGUE: So, even a slim, lean, handsome physically fit person could have 30 pounds of fat in him?
MONICA HALL-PORTER: Absolutely.
DAVID POGUE: Next up, the third most common macromolecule type…
Oh, this is my kind of food group.
MONICA HALL-PORTER: Sugar.
DAVID POGUE: Does this count as carbs?
MONICA HALL-PORTER: Absolutely.
DAVID POGUE: While I would have thought I was sweeter, turns out, on average, there’s only about two pounds of carbs in me.
Glucose is the most abundant carb in the human body. It circulates to provide energy for cells.
Now we’re talking carbs, carb city, carb heaven, carb central.
MONICA HALL-PORTER: We are in the bread aisle, my friend.
DAVID POGUE: I like it.
MONICA HALL-PORTER: We can toast this up and put some butter on it.
DAVID POGUE: Many glucose molecules joined together can make a plant starch, the kind you find in cereals and root vegetables. It’s the most common carb in the human diet.
So, did I under…
DAVID POGUE: Hey! We’re working here.
MONICA HALL-PORTER: So, we’ve got lipids…
DAVID POGUE: Yeah.
MONICA HALL-PORTER: …proteins…
DAVID POGUE: Yeah.
MONICA HALL-PORTER: …and carbohydrates.
DAVID POGUE: Yeah, the three macromolecules of the human body.
MONICA HALL-PORTER: Right, but we are missing one.
DAVID POGUE: There’s another one?
MONICA HALL-PORTER: Yeah, we don’t have anything that’s representative of nucleic acids.
DAVID POGUE: Nucleic acids are better known as D.N.A. and R.N.A. D.N.A. is the famous double helix. It’s usually two long chains of molecules that wrap around each other. It contains genetic instructions for making proteins.
R.N.A. is often a long molecular chain, as well. If D.N.A. is the cookbook, R.N.A. is the chef, reading D.N.A.’s instructions for proteins, gathering the ingredient amino acids and assembling them in the right order, in a macromolecular “protein printing” machine called a “ribosome.”
Life on Earth exists in a spectacular variety of forms, but in the end, it all depends on the arrangement of a handful of different small molecules, the nucleotides in the nucleic acids D.N.A. and R.N.A.
And we are now arriving at the D.N.A. aisle.
MONICA HALL-PORTER: Alrighty.
DAVID POGUE: And why strawberries?
MONICA HALL-PORTER: Well, strawberries actually have eight copies of each chromosome per cell, so, relative to other fruits, strawberries are actually very rich in D.N.A.
DAVID POGUE: Wow. All right. Here’s our “D.N.A.e-berries.”
MONICA HALL-PORTER: Alrighty.
DAVID POGUE: Actually seeing D.N.A., you know, the code of life has always seemed beyond the reach of ordinary folks. You can’t just find some, can you?
So, when you said we were going to extract D.N.A. from strawberries, I figured we would go to some humming, high-tech lab with millions of dollars of equipment.
MONICA HALL-PORTER: No, actually D.N.A. extraction from strawberries is something that can be achieved at home.
DAVID POGUE: As it turns out, using some easily available household items, like plastic bags, detergent, rubbing alcohol, cheesecloth and strawberries, along with a little bit of waiting time, you, too, can catch a glimpse of the code of life, D.N.A.
MONICA HALL-PORTER: There it is. You’ll actually see an accumulation of white, stringy substance.
That’s actually a very crude prep of D.N.A.
Basically, what’s going to happen is it’s going to clump on the end of your glass rod.
DAVID POGUE: Strawberry D.N.A. slime, right there.
Pretty amazing! And so are the other three macromolecules that make up my body. But all their wondrous complexity raises a deeply mysterious question: How did chemistry give rise to biology?
How did life get its start?
A famous experiment, in 1952, suggested the answer might not be that hard to find. At the University of Chicago, graduate student Stanley Miller, with help from his doctoral advisor, Harold Urey, mixed what were then thought to be the dominant ingredients of Earth’s early atmosphere: methane, ammonia and hydrogen, inside some sealed glassware. Boiling water added water vapor to the mix. Then, Miller created sparks between electrodes, simulating lightning, and let the mixture cool and condense.
After running the experiment for a week, Miller found five amino acids, some of them critical building blocks of proteins.
JACK SZOSTAK: You know, it was a dramatic breakthrough, at the time, for people to realize amino acids could be made in such a simple way.
DAVID POGUE: At Massachusetts General Hospital, Jack Szostak runs one of the several research labs around the world that are trying to figure out how chemistry gave rise to biology.
ANNA WANG (UNSW Sydney): So, this is like increasing the amount of sodium hydroxide. And so, increasing…
JACK SZOSTAK: Oh, okay.
DAVID POGUE: Today, it’s clear even the Miller-Urey experiment, while groundbreaking, just scratched the surface of the problem.
JACK SZOSTAK: In retrospect, it kind of fooled people into thinking that the answer might be easier than it turned out to be.
And once you’ve got the right chemicals, then what?
DAVID POGUE: Right, right.
JACK SZOSTAK: How do a bunch of chemicals get together and start acting like a cell?
DAVID POGUE: A key requirement seems to be a container. All life on Earth, from the simplest to the most complex, is made of cells with outer membranes.
So, on the road to life, how did that happen?
Scientists like Anna Wang, a former postdoc in Jack Szostak’s lab, now a professor at UNSW, Sydney, have been working with a simple molecule that is one of the prime suspects.
It’s also present here…
ANNA WANG: Wow.
DAVID POGUE: …shaped into bars, in a wide variety of colors and scents…
Smells good in here.
ANNA WANG: Smells amazing.
DAVID POGUE: …at Molly’s Apothecary, outside of Boston.
ANNA WANG: Oh, that’s wonderful.
DAVID POGUE: That’s right: soap.
Soap’s interesting, because a soap molecule is a combination of two different types of molecules, called polar and non-polar. For example, water molecules are polar. Each one has a concentration of electrons in one part, making it negative, which leaves another part more positive. That’s polarity. And it makes water molecules want to stick together, each negative part attracted to another molecule’s positive part.
An oil molecule, made up of carbon and hydrogen, is an example of a non-polar molecule. It has an even distribution of electrons: no polarity and less stickiness between molecules. In fact, polarity is why oil and water don’t mix. The polar water molecules stick together, keeping the oil molecules at bay. The less dense oil floats on top.
That’s also why trying to clean oily grease off your hands with water alone, doesn’t work very well.
It actually won’t come off, it’s super oily.
The two just don’t interact. And that’s where soap molecules come in. They’re hybrids. At one end, are some negatively charged, electron-rich oxygens, ready to interact with polar molecules, like water, but the rest is a long, non-polar hydrocarbon tail, with no positive or negative charge. It’s more comfortable mixing with other non-polar molecules, like grease.
Put some soap on your greasy hands…
…and the soap’s non-polar tails stick into the grease, while its polar heads act like handles, ready to interact with the water, taking the grease along for the ride.
Here’s another interesting soap fact. Drop some soap into water and the molecules form little balls called “micelles,” with their water-loving polar heads sticking out and their water-hating non-polar tails sticking in.
That naturally occurring little container has piqued the interest of scientists like Anna. Back at the lab, she adds some soap molecules to water containing short fragments of R.N.A. They’ve been tagged with a molecule that makes them glow.
Why R.N.A.? The current scientific consensus is that a primitive form of R.N.A. may have been the first molecule with the ability to replicate itself, jump-starting evolution.
ANNA WANG: Now, we’re going to go look at it under the microscope.
DAVID POGUE: …the microscope room…
ANNA WANG: Let’s go.
DAVID POGUE: …where Anna loads up a sample she prepared yesterday.
ANNA WANG: So, this is what our soap molecules have self-assembled into overnight.
DAVID POGUE: What are they? Bubbles?
ANNA WANG: Yes, they are almost like bubbles. And so, what we are looking at here is not the soap molecules themselves but what they’ve been able to trap inside these cell-sized structures.
DAVID POGUE: Overnight, the soap micelles have self-assembled into larger spheres, trapping the fluorescing R.N.A. inside. And if we could zoom into one of them, we’d see that it actually consists of two layers of soap molecules, arranged with the water-loving heads toward the inside and outside, and the water-hating tails brought together.
ANNA WANG: When you have molecules that have a polar head group and a non-polar tail, but you don’t give them any oil to interact with, the oily tails actually want to interact with each other, and so you end up forming these bilayer structures.
DAVID POGUE: Wait, so these are soap molecules and these are also soap molecules?
ANNA WANG: Yeah.
DAVID POGUE: And they like to assemble into this position?
ANNA WANG: Yeah, that’s right. So, they like to form these really thin envelopes, and you can imagine this structure extending onwards and onwards and curving around and forming a sphere. And that’s what we’re seeing here. We’re seeing this bilayer structure, encapsulating some green-dyed R.N.A. molecules.
DAVID POGUE: This lipid bi-layer structure isn’t alive, but it’s familiar to biologists. It’s similar to the bilayer structure of the membranes that surrounds something that is alive, cells.
Of course, those are much more complicated and more stable containers, better at keeping things in or out, though that feature comes at a price.
ANNA WANG: If you take the membranes that we have now, but get rid of all the highly evolved protein machinery, what you’re left with is just an inert sack. It can’t grow, it can’t divide. It can’t even get nutrients in and out.
DAVID POGUE: That’s why, in the days of proto-life, less-stable membranes built out of simpler molecules, like soap, may have been an advantage.
Anna shows me an example.
ANNA WANG: So, what I am about to do is I have some soapy water in here, and I’m just going to add it. What happens is the soap molecules start incorporating onto the existing membrane.
DAVID POGUE: Look at this. Look at this.
ANNA WANG: Yeah.
DAVID POGUE: It just split.
ANNA WANG: They look pretty spherical now, but they’re starting to wiggle a bit. And all of a sudden, it looks like they might melt.
DAVID POGUE: Cell division.
Our cells grow and divide, because we have something giving instructions.
ANNA WANG: Yes.
DAVID POGUE: But you’re saying that, billions of years ago, none of that existed.
ANNA WANG: There’s none of that in here. So, what we’re kind of simulating is a condition where maybe these protocells have floated somewhere down the stream, and they’ve come across a pool of excess soap molecules, and these soap molecules can join the membrane and grow it.
So, I think what it means is that we can still get simple cells to divide by purely physical mechanisms, and that’s what we’re trying to understand in the field, like how do you get to do things that kind of seem like life and mimic life but without any biology?
DAVID POGUE: In the early days of Earth, soap or similar molecules may have self-assembled into cell-like containers.
Do they have the bilayer thing already?
JACK SZOSTAK: They have the bilayer membrane.
DAVID POGUE: But Jack Szostak realizes that’s just a start. There are many more steps on the road from chemistry to biology.
JACK SZOSTAK: Once you got the right kinds of molecules, which are pretty simple, they can assemble into membranes. But they can’t actually start to do anything interesting in terms of, like, getting more complicated and being more, like, more and more advanced life, until you have genetics.
DAVID POGUE: Yeah.
JACK SZOSTAK: You needed hereditary materials, something like R.N.A. or D.N.A.
And once you’ve done that, you have cycles of replication, because that’s got to go on inside this protocell. And it has got to happen just by chemistry and physics, because there were no enzymes. There was no evolved machinery, right?
DAVID POGUE: Right.
JACK SZOSTAK: So, in a sense, the answer has to be simple.
DAVID POGUE: Yeah.
JACK SZOSTAK: And we just have to figure out how it works.
DAVID POGUE: Scientists like Jack and Anna are searching for the mysterious road that led not only to life but to the mechanism that’s allowed it to overcome adversity, evolution.
Today, some scientists wonder, what if we could harness evolution’s creative power to solve some of our own challenges?
FRANCES ARNOLD: Nature is constantly changing…
DAVID POGUE: Hi, boys.
FRANCES ARNOLD: …because there is this tremendous effort to survive. And if you can harness that power, that innovation that nature is doing, and direct it in a beneficial way, then we can use that power of innovation to solve some of our really tough problems.
DAVID POGUE: Harnessing the innovative power of evolution is at the heart of the work of chemical engineer Frances Arnold, of Caltech, in Pasadena, California.
That could be a huge deal in the world.
FRANCES ARNOLD: I hope so.
DAVID POGUE: And she’s used it to engineer new molecules to solve a wide range of problems, from the search for new antibiotics, or methods to convert waste into biofuels, to teaching cells to bond elements in ways never before seen in nature.
FRANCES ARNOLD: So, do come if you are interested in the process of protein engineering, because that’s the future. So, all of you….
DAVID POGUE: She’s achieved her successes by discovering new catalysts, the materials that speed up chemical reactions without getting consumed by them.
In living things, catalysts are called enzymes, for example the protein rubisco. Enzymes help facilitate the reactions that make life possible.
FRANCES ARNOLD: The reason that you and I can sit here and talk is that we have thousands of catalysts in us, proteins that can convert the food we eat into the thoughts that you think and the motor mouth, right? These are catalysts that do all this chemistry. These are chemical transformations that make life possible.
DAVID POGUE: In fact, they work so well, engineers and scientists have wanted to find a way to co-opt the idea, to create new enzymes that would do our bidding, assisting reactions that aren’t found in nature at all.
The question is how?
FRANCES ARNOLD: Many scientists and engineers feel that in order to design a new product, you sit down and you calculate, you know, the right angles and the right weights and loads.
I come from a different point of view, that these very complicated things are the products of evolution. So, I say, “Let’s just go straight to the answer, using this gift given to us.”
DAVID POGUE: Frances uses an approach called “directed evolution.”
FRANCES ARNOLD: One way to think about directing evolution is it’s like breeding. It’s like breeding cats or dogs.
DAVID POGUE: With a specific end goal in mind, she starts with D.N.A. that encodes for some protein catalysts that have some promising traits, depending on what she’s looking for. The D.N.A. gets copied in a way that produces random mutations. She puts that into microorganisms that multiply and produce a variety of slightly different proteins.
FRANCES ARNOLD: So, you have a gene, the organism breeds the gene, makes the proteins, and they’re all slightly different, just like your children. But now, I can decide who goes on to parent the next generation, because I measure what those proteins do.
DAVID POGUE: Frances tests the results to see if any represent a step in the right direction. If so, that becomes the new starting point, and she repeats the process.
FRANCES ARNOLD: To see how quickly you can train enzymes, that’s what we’re doing, we’re training them, we’re breeding them to do something that perhaps nature never did before.
When you discover that they’ve learned how to do that and they do it better than any human can do, it is so exciting.
DAVID POGUE: To see how directed evolution is applied outside the lab, Frances suggested that I contact one of her former students, Pedro Coelho. Along with a partner, she and Pedro founded a company, Provivi, based in Santa Monica. Pedro is the C.E.O.
Provivi makes a chemical to fight this agricultural pest, the fall armyworm.
PEDRO COELHO: It’s a pest that is native to the Americas, but in the last three years, it’s invaded all of Africa, and now, all of Asia, going from India to China. And it’s a very difficult pest to control, because once it infests the corn, it hides inside of the corn plant where the insecticides can’t touch it.
DAVID POGUE: But Provivi’s chemical isn’t a pesticide; it doesn’t kill anything, instead, it disrupts the way fall armyworms mate.
Here’s how it works: fall armyworms eventually become adult moths and that’s when they mate.To attract males, female moths release a pheromone, a molecule that acts as a chemical signal.
PEDRO COELHO: So, the female moth will release a little bit of pheromone, and then the male will pick up that signal with his antenna and will fly towards her to mate and reproduce.
DAVID POGUE: She uses only a small amount, but it is incredibly potent. It can attract males from up to a mile away.
FRANCES ARNOLD: These are complicated molecules. These are the Chanel® No 5 of insects.
DAVID POGUE: But such a powerful “sex perfume” can be become a means of control.
FRANCES ARNOLD: So, imagine now you come with a bottle of Chanel No 5, and you spray it everywhere, then he can’t find her, and they don’t mate and have caterpillars.
DAVID POGUE: Provivi has figured out how to replicate the fall army pheromone and put it into a slow-release spray for crops, which you have to imagine is very confusing for the male moths.
They have so much trouble finding females that in the end there are fewer eggs and worms.
So, you’re not killing these things, and you’re not driving them away, you’re just confusing them.
PEDRO COELHO: Yeah, so it’s not a repellant, and it’s not a kill agent, it’s simply a mating disrupter.
DAVID POGUE: Pedro tells me using pheromones to combat pests isn’t new, but until now, it’s been expensive and therefore limited to high-value smaller crops like apples or grapes.
So, the real breakthrough at Provivi isn’t using pheromones but making them inexpensively. They’ve studied the enzyme catalysts the insect uses to make the pheromone and moved the genes for those enzyme catalysts into yeast. Then, through directed evolution, they optimized those little yeast cell factories for larger scale production in vessels similar to those used for brewing beer.
PEDRO COELHO: And the key is that by just changing the microbe, we can make many different pheromones. But using the same infrastructure, which gives us the economies of scale, should make this cost effective.
DAVID POGUE: Making it possible to use on staple crops grown around the world, like corn and rice.
PEDRO COELHO: Our mission, very much, is to take this proven tool of pheromones to the largest markets of agriculture, which are the staples of humankind.
DAVID POGUE: Companies like Provivi aren’t the only sign directed evolution and cell factories are having a big impact on manufacturing.
FRANCES ARNOLD: Well, I teach this course, called Reaction Engineering, which is how do you take chemical reactions and scale them up?
DAVID POGUE: In 2018, Frances Arnold won the Nobel Prize in Chemistry, for her pioneering work in directed evolution.
Is this idea of chemistry and biology to manufacture stuff, is that catching on these days?
FRANCES ARNOLD: It is. It most definitely is. I think the future is so exciting, because now what happens is with these tools of being able to manipulate D.N.A. and the code of life, really, we can now merge all these beautiful mechanisms of the biological world with the inventions of human chemistry. And that way it merges in new innovations.
DAVID POGUE: That both chemists and biologists have a lot to learn from each other should come as no surprise, but what is surprising is that biology would arise out of chemistry at all.
Look at this. Look at this. Cell division.
The blueprints of life.
The origin of life remains one of the great unsolved mysteries of science. Was the mix of chemicals on early Earth destined to give rise to life? And once it started, was the road that lead to the chemical complexity of photosynthesis and the harnessing of the power of the sun…
LISA AINSWORTH: Probably the most important process on the planet.
DAVID POGUE: …the only road to be taken? Are we alone in the universe, or just the local branch of Cosmic Bio-Chem? The answers to questions like these will only be found through science, as we go Beyond the Elements.
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(Sprout Germination) © DimaBalanFilms/Pond5
- Lisa Ainsworth, Frances Arnold, Amanda Cavanagh, Pedro Coelho, Monica Hall-Porter, Kerry Hanson, Stephen Long, Donald Ort, David Pogue, Paul South, Jack Szostak, Anna Wang