Chemists studying the origins of life have come a long way since Urey and Miller’s famous experiment in 1963. They showed that an electric charge could jump-start the formation of amino acids in a flask containing just methane, ammonia, hydrogen and water. Now chemist have found routes to many of the molecules found in biology, including a prebiotically plausible synthetic pathway to a pyrimidine ribonucleotide, starting with only simple organic molecules and inorganic phosphate. It seems that we are getting closer to understanding how a prebiotic soup of chemicals turned into biology.
But some origins of life researchers are not so sure that organic reactions carried out in pristine glassware and laboratory conditions will get us there alone. They say purely understanding synthetic steps doesn’t really explain why and how life started. Rather than isolating organic reactions, ‘we’re trying to explain why a whole collection of chemicals with particular interconversion reactions are present in a mutually supporting network, that is the universal foundation of life, and why all the other chemicals are not part of that network’, says Eric Smith, an origins of life researcher atthe Earth Life Science Institute (ELSI) at the Tokyo Institute of Technology in Japan and theCenter for the Origin of Life at Georgia Institute of Technology in the US.
Prebiotic chemistry could have involved vast systems with a lot of reactions and components
Irena Mamajanov coined the expression ‘messy chemistry’ to describe this approach. She was formerly an investigator at the ELSI and is now working in industry. The messy label is not a comment on the untidiness of her or her colleagues’ benches, but she says it describes ‘complex systems chemistry as applied to prebiotic [environments]’. Systems chemistry is normally used to model outcomes in small defined chemical systems, but Mamajanov says prebiotic chemistry could have involved ‘vast systems with a lot of reactions and components’, where emergent properties are difficult to predict. Rather than looking for precise reactions, she thinks it’s now crucial to start to understand the mechanism of organisation in complex systems, which may provide clues to how these ultimately developed into life.
The prevailing chemical origins theory today is some version of the ‘RNA world’ – the idea that life grew out of the synthesis of RNA molecules. They are uniquely able to replicate themselves through base-pairing and could have acted as catalysts for this and other chemical reactions before the existence of protein-based enzymes. Smith, who previously worked at the Santa Fe Institute in the US, says this is missing the point and has’created this enormous focus on getting to RNA by any means’. It’s not that the chemical details don’t matter, he says; they matter enormously, but it doesn’t address the principles that organised molecules into life.
Today, most proponents of the RNA world theory do not suggest the molecule could have led to life in isolation. ‘I don’t think anyone believes that anymore,’ says Matthew Powner, an organic chemist from University College London in the UK. Most would support a ‘softer’ version that acknowledges other molecules now found in biology, such as peptides and lipids, would have also played an early role – and even inorganic minerals could have acted as catalysts. For Mamajanov and others taking a systems chemistry approach, the task is to understand the important and necessary steps that occurred to allow the RNA world to come about.
It’s not an enzyme yet, but it is some proof of principle
To probe the possibilities for this earlier messier chemistry, Mamajanov has been investigating how unorganised hyperbranched polymers, formed over wet and dry cycles, could have acted as proto-proteins on prebiotic Earth. Repeated wet and dry conditions are likely to have been a feature of some environments on the early Earth, such as surface pools or geysers, and have been put forward as the ideal means of driving condensation reactions. Using polyesters, Mamajanov found that after reaction linear molecules tended to be hydrolysed and degrade, but branched polymers were more stable and are often soluble because they don’t pack efficiently into crystal structures. ‘Those hyperbranched polymers could have been precursor to enzymes,’ she suggests.
Hyperbranced polymers – such as apolyethyleneimine (left) and a polyester (right) – could have acted as proto-proteins
Mamajanov also synthesised globular hyperbranched polyesters, incorporating hydrophobic groups and a tertiary amine to serve as an active reaction site. She was also able to show these molecules could mimic the kinds of hydrophobic pockets found in proteins and were capable of catalysing the Kemp elimination reaction – a well-studied benzisoxazole ring-opening reaction, increasing the rate of the reaction by a factor of three. She also synthesised hyperbranched polyethyleneimine (repeating units of an amine groups spaced between two carbons), augmented with metal sulfide nanocrystals. These were capable of photosynthetic reactions. ‘Of course, it’s not an enzyme yet, but it is some proof of principle,’ says Mamajanov.
Autocatalytic chemical evolution
Chemist Nicholas Hud from the Georgia Institute of Technology thinks the early Earth would have been covered with a giant oil slick of simple organic molecules, so an important question is how certain types of molecules crucial to life became enriched or segregated, before replication mechanisms were in place. Smith says we need to look towards auto-catalytic systems where the products of the reaction amplify the rate of their production. ‘[It’s] the only likely thing you can invoke in very early unsupervised chemistry to concentrate a lot of your material into certain centres, so that you have an excess of particular building blocks.’
It is natural selection acting on populations of chemicals that are continuously reacting and forming products
This may have also led to a type of chemical evolution, although not fuelled by the replication and selection crucial to Darwinian evolution. ‘It is natural selection acting on populations of chemicals that are continuously reacting and forming products. It’s not as sophisticated as biological evolution, obviously,’ says Arthur Omran, a chemist from the University of North Florida in the US. But in conditions where the environment constantly cycles and given long periods of time, he is sure something akin to evolution will occur.
Source: © 2022 Christian Mayer
Cycling the pressure (to mimic tectonic fault zones) on reaction mixtures can stabilise membrane-like vesicles
Christian Mayer from the University of Duisburg-Essen in Germany has carried out some interesting experiments that illustrate how this could have occurred in complex chemical systems over multiple cycles of changing conditions. He put a mixture of 12 proteinogenic amino acids along with C-18 long chain fatty acids, water and carbon dioxide in a high pressure cell at 120°C. Cycling the pressure between 100 and 70bar he attempted to mimic the kind of environment that might be found in tectonic fault zones, where tidal flows or geysers cause pressure cycling. In these conditions oligopeptides of varying length will spontaneously form and some will help to stabilise membrane-like bilayer vesicles that are also produced when the fatty acids arrange themselves around droplets of supercritical carbon dioxide as the pressure rises.
After three weeks Mayer analysed the peptides that had formed and survived over 1500 cycles. He found that those with hydrophobic and hydrophilic elements that mirrored the amphiphilic properties of the fatty-acid membrane were more easily integrated into the vesicle, and protected from hydrolysis. There was also selection for vesicle size, with smaller vesicles surviving better than larger ones. Mayer even found some level of functionality beginning to arise: for example some peptides formed channels in the vesicles that would allow water and ions to pass through and release osmotic pressure, in turn providing a survival benefit for those vesicles.
Mayer thinks the interconnected selection principles of both peptides and vesicles is a ‘powerful force’ leading to a chemical evolution process and greater order and complexity. The anchoring of proteins through membranes is also a feature of modern biology. ‘We know that nowadays many enzymes work according to this principle,’ he says.
Another central and defining feature of life is its ability to harness energy from the environment – its metabolism. In the 1920s, before much of the chemistry that underpins the RNA world was understood, Soviet biochemist Alexander Oparin proposed a ‘metabolism first’ hypothesis of the origins of life. He supposed that some version of the reactions that enable energy to be used by life must have pre-dated replicating molecules. As well as seeking the components of the biopolymers found in life today, chemists studying complex systems also have one eye on signs of such early metabolic reactions.
If this is truly a proto-metabolic system that is related to life, I’m looking at the first five minutes
One of the chemical systems that many chemists have suggested as a feedstock for the biomolecules needed for life is the formose reaction – the autocatalytic reaction of formaldehyde with a calcium hydroxide catalyst that leads to the formation of sugars via numerous intermediary steps. It provides a possible route to the ribose sugar that makes RNA from a simple organic molecule. But recent work has made Omran question whether, rather than a source of ribose, the reaction may have been a source of the molecules making up the nascent metabolism that would go on to sustain life.
Omran experimented with the formose reactions, but found in reality only 1% of products were sugars – the rest being products of the competing Cannizzaro process in which formaldehyde and other products disproportionate into organic acids and alcohols. ‘There is no divorcing these reactions,’ explains Omran. He did end up with significant amounts of biologically relevant organic hydroxy acids that are still found at the core of modern metabolism, including lactic, glycolic, oxalic and acetic acids. ‘In this formose system, sugars are broken down, which life likes to do for energy and other things,’ says Omran. It’s very far from the complex metabolic systems seen in biology today but may have set the stage. ‘If this is truly a proto-metabolic system that is related to life, I’m looking at the first five minutes,’ he says.
Mayer also thinks his vesicles suggest a path to a very primitive cell metabolism. His pore-containing vesicles would provide compartments that would sustain a chemical gradient and allow energy to be harnessed. ‘ You could imagine a process where the passage of water molecules or ions through the pore could generate energy-rich conformations, which could be used for [the] recruitment of a primitive energy metabolism,’ suggests Mayer. This in turn could then provide the energy needed to synthesise RNA molecules: ‘an ideal basis for an RNA world’, he adds.
As with all theories of the chemical origins of life, these ideas are all highly speculative, but are providing a new lens from which to explore the possibilities. Although there are limitations to a messy approach – the main one being the difficulties in analysing the hundreds and thousands of products that messy experiments can potentially produce. ‘What we do right now is focus on a fraction of them… we ignore many other compounds: for example compounds which have been produced by a combination of our amphiphiles with the amino acids,’ explains Mayer. ‘Otherwise, we get to a problem that we cannot solve.’ Of course, this mean that even a messy approach could be missing a crucial product or reaction. Mamajanov admits the analysis of her experiments is ‘not straightforward’. She has used a statistical technique called principal component analysis, which allows mass spectroscopy data to be clustered into compounds of similar types.
There may be molecules that came before those that we have in life today that were very important(Video) Green Day - Macy's Day Parade [Official Music Video]
Unlike some of his colleagues, Hud isn’t going quite as messy in his experiments. ‘At some point, you have to balance the difficulty of having all the molecules you think that might have been present and looking for the next level of reaction and dealing with the chemistry of that,’ he says. His approach is to consider chemical pathways to life other than those currently part of biology. ‘There may be molecules that came before those that we have in life today that were very important, and they might have associated even better than the ones that we have in life today and given everything a jumpstart.’
Source: © 2021 American Chemical Society
Hud and colleagues have made ’protonucleic acids’ from depsipeptides in plausible prebiotic conditions
One example is the concurrence of alpha-hydroxy acids with amino acids on early Earth. Hud and colleagues have shown that in cycles between wet and dry conditions, they easily form amide bonds leading to depsipeptides – oligomers with a combination of ester and amide linkages. Hud has suggested thesecould have provided an intermediate stop-gap and an easier synthetic path to polypeptides before the emergence of enzymes. He is now taking a similar approach to making a proto-RNA polymer with an alternative backbone and heterocyclic bases. In 2021 he and his collaborators came up with a nucleic acid with a depsipeptide backbone, which forms under prebiotic conditions and oligomerises spontaneously when dried. It is then capable of self-assembly into supramolecular structures that have base pairing.
Powner, a synthetic organic chemist, is aware of the criticism sometimes levelled at those like himself who do ‘clean reactions’ to probe the origins of life, and he is certainly under no illusion that these were the conditions present on the prebiotic earth. ‘The easiest way for me to understand the nuances of how to build molecules is to design and evaluate reactions carefully, methodically and accurately,’ he explains. ‘We think that will give us the most information to move forwards.’ He is slightly puzzled at the idea of throwing everything in at once. ‘The idea that we would run reactions where we couldn’t test the exact outcome doesn’t make scientific sense as a chemist.’
The ‘messiness’ becomes apparent in the interconnected syntheses of ribonucleotides, amino acids and lipid precursors
He acknowledges that extracting parts of a complex chemical system that led to life might obscure the bigger picture, but his conventional synthetic approach is also providing clues to how mixed chemical systems propelled life forward. This became apparent from Powner’s ground-breaking synthetic pathway to a pyrimidine nucleotide, carried out when he was a student in John Sutherland’s research group at the University of Manchester in 2009. They found that although inorganic phosphate is only incorporated into the nucleotides at a later stage, its presence from the start is essential, to act as a catalyst and buffer. ‘This is when we started thinking about the chemistry we were applying to the origin of life in a systemic way,’ says Powner. Further work from Sutherland, who has since moved to the University of Cambridge, showed in 2015 that precursors to pyrimidine nucleotides are also able to form lipids and amino acids.
The idea that we would run reactions where we couldn’t test the exact outcome doesn’t make scientific sense as a chemist
Powner’s more recent work has focused on designing synthetic pathways that avoid undesirable by-products but can proceed without resorting to artificial multi-step processes unlikely to be plausible in prebiotic scenarios. For example, his group has shown a route to ribonucleotides from two- and three-carbon sugars in complex mixtures that proceeds via stable crystalline aminals (compounds having two amino functional groups attached to the same carbon). This step allows for separation and purification along the way. They also found that aminal formation could lead to proteinogenic amino acids, suggesting a unified chemical origin.
Powner has also worked on making the sorts of alternative nucleotides to RNA that Hud has proposed as a stepping-stone to RNA. He recently synthesised an analogue containing the four-carbon sugar threose, rather than ribose. But given organic chemists are increasingly showing plausible synthetic routes to current biopolymers he wonders if these additional steps are needed. ‘If you can make the biological ones, then you’re on a simpler route towards the end goal, which is life as we know it,’ he says.
Smith thinks it may take advances in computational chemistry and automated high-throughput robotic methods to make more systematic progress in understanding the complex systems that allowed chemistry to become biology. ‘For different chemical reaction mechanisms that we think are likely to be of interest, we could use high-throughput robotics to just systematically sample [how they proceed alongside] the different minerals, their different rock environments, [and their] intersections and interfaces, and just build this enormous almanac of what is known to happen,’ he suggests.
But messy chemistry still represents a minority approach to origins of life research. Mamajanov, who is currently not working in academia, hopes she may be able to continue her work if the field becomes more accepting of the sort of analytical methods she uses and starts to look at the bigger picture. According to Omran, interest is now growing. ‘I am biased, but I think it’s the future of our field… if you want to get a viable idea of what could have happened in nature, you’ve got to dirty it up a little!’
Rachel Brazil is a science writer based in London, UK
What is the Chemistry of Life? “As basic building blocks of life, all living organisms use nucleic acids, proteins, lipids, and carbohydrates, as well as a variety of small molecules such as metabolites, messengers, and energy carriers.How did chemistry impact in your life? ›
The industrial applications of chemistry directly affect our daily lives—what we eat, what we wear, our transport, the technology we use, how we treat illnesses and how we get electricity—to name just a few. Research is constantly deepening our understanding of chemistry, and leading to new discoveries.What are the 5 chemicals of life? ›
The elements carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus are the key building blocks of the chemicals found in living things.What is the chemical origin of life? ›
The chemical origin of life refers to the conditions that might have existed and therefore promoted the first replicating life forms. It considers the physical and chemical reactions that could have led to early replicator molecules.What is soul chemistry? ›
Soul Chemical. A chemical squeezed from the pineal gland of a recently deceased Survivor. During a Rush, the moment The Blight comes within 16 metres of a Survivor who is repairing or healing, trigger a tremendously difficult Skill Check. for that Survivor.What chemicals form life? ›
Life functions through the specialized chemistry of carbon and water, and builds largely upon four key families of chemicals: lipids for cell membranes, carbohydrates such as sugars, amino acids for protein metabolism, and nucleic acid DNA and RNA for the mechanisms of heredity.How does chemistry relate to everyday life? ›
Chemistry is a big part of our everyday life. One can easily observe this branch of science in different spheres of human life such as in the food we eat, the air we breathe, the various cleansing agents we use, so much so that even human emotions are sometimes a result of chemical reactions within our body!What would happen if chemistry is absent in our lives? ›
Without chemistry people would die much younger from diseases such as bubonic plague, since we wouldn't have antibiotics. We wouldn't have vaccines, so people would still contract terrible illnesses such as smallpox and polio. Even a simple skin infection might lead to death.What is chemistry in love? ›
Chemistry in a relationship is an intense feeling of connection. Romantic partners can build chemistry over time by practicing open communication and developing trust.What chemicals keep you alive? ›
By mass, about 96 percent of our bodies are made of four key elements: oxygen (65 percent), carbon (18.5 percent), hydrogen (9.5 percent) and nitrogen (3.3 percent).
Carbon is the basis of all biochemical compounds, so carbon is essential to life on Earth. Contrary to popular belief, carbohydrates are an important part of a healthy diet. They are also one of four major classes of biochemical compounds. Carbohydrates are the most common class of biochemical compounds.What is the real origin of life? ›
The origin of life on Earth (and possibly on other planets) is the result of the chemical evolution of the universe. Generations of stars have enriched the interstellar medium (ISM) with atomic elements that can form simple molecules even in the exotic conditions found in outer space.What is the theory of life? ›
Life history theory explains the general features of life cycle, i.e., how fast the organism grows, at what age it matures, how long it lives, and how often it reproduces. The theory is central to evolutionary ecology, as it directly deals with natural selection, fitness, adaptation, and constraint.Who created origin of life? ›
Although English naturalist Charles Darwin did not commit himself on the origin of life, others subscribed to hypothesis 4 more resolutely.What is the fuel of soul? ›
“Love is fuel for the soul.”Where does the soul reside in the human body? ›
The soul or atman, credited with the ability to enliven the body, was located by ancient anatomists and philosophers in the lungs or heart, in the pineal gland (Descartes), and generally in the brain.What is a soul made of? ›
The Epicureans considered the soul to be made up of atoms like the rest of the body. For the Platonists, the soul was an immaterial and incorporeal substance, akin to the gods yet part of the world of change and becoming.What are the 7 life forms? ›
Life processes: These are the 7 processes all living things do - movement, reproduction, sensitivity, nutrition, excretion, respiration and growth.What caused life to form? ›
These chimney-like vents form where seawater comes into contact with magma on the ocean floor, resulting in streams of superheated plumes. The microorganisms that live near such plumes have led some scientists to suggest them as the birthplaces of Earth's first life forms.What are the 4 life substances? ›
The most abundant substances found in living systems belong to four major classes: proteins, carbohydrates, lipids, and nucleic acids.
While there are many external factors that can influence your mood like the weather and your relationships, there are also four main chemicals that play a big role, including serotonin, dopamine, adrenaline and oxytocin.Why is chemistry so hard? ›
The primary reason chemistry is so hard is because of the topic progression. You really have to fully understand several topics before you can fully understand other topics. It's important to keep in mind, memorization isn't the key here. There's a certain element of memorization.What is the value of 1 mole? ›
The value of the mole is equal to the number of atoms in exactly 12 grams of pure carbon-12 (12 g C = 1 mol C atoms = 6.022 × 1023 C atoms).Why is chemistry so great? ›
Learning chemistry will reveal a whole new understanding of how our world works. Anything that has matter breaks down into chemical building blocks. If chemistry did not exist, we wouldn't understand why leaves change color in the fall, producing and preserving food, and so on.Why do I need chemistry? ›
Chemistry helps you to develop research, problem solving and analytical skills. It helps to you challenge ideas and show how you worked things out through logic and step-by-step reasoning. Chemistry often requires teamwork and communication skills too, which is great for project management.Why can't we live without chemistry? ›
Chemistry plays an important role in the world we know.
Chemistry enables us to have mobile phones, cars, home care products, clothes. It provides us with more food and healthier food, it purifies the water we drink, it makes our lives cleaner. Chemistry is all around us.
Without chemistry we wouldn't have light bulbs, mobile phones, Facebook or Twitter. Much of the food we eat and clothes we wear involve chemists and chemistry too. If we had never studied chemistry we wouldn't have liquid oxygen.What does lack of chemistry mean? ›
Unlike a lack of compatibility, a lack of chemistry doesn't repel—it simply results in a lack of emotional intensity. Things just feel kind of dead and boring. Chemistry is also reflected in the bedroom. A lack of chemistry will mean boring, emotionless sex.What causes intense chemistry with someone? ›
Chemistry is born of several different factors like physical attraction, mental stimulation, shared values and interests.What makes a man fall deeply in love with a woman? ›
Physical attraction, sexual compatibility, empathy, and emotional connection are key to making a man fall in love with a woman.
One of the major causes of chemistry in relationships is that both people share mutual interests, especially for the things that matter to them. The result of this is that they can spend time together, and every time they do so, they have a ton of activities to keep busy.
People with clinical depression often have increased levels of monoamine oxidase A (MAO-A), an enzyme that breaks down key neurotransmitters, resulting in very low levels of serotonin, dopamine and norepinephrine.What is the happiest chemical? ›
“Dopamine is often known as the reward or pleasure chemical,” says Michela, revealing that the brain releases this chemical during activities that are considered pleasurable, such as exercise or eating, rewarding us with a hit of happiness.
production of serotonin – serotonin is a hormone that affects your mood, appetite and sleep; a lack of sunlight may lead to lower serotonin levels, which is linked to feelings of depression.What are the three elements of life? ›
The four basic elements of life are: Oxygen, hydrogen, nitrogen and phosphorus. These four elements are found in abundance in both the human body and in animals. There are other elements that compose the human body, but the four we've highlighted participate in all life processes.What is the most essential compound needed to sustain life? ›
1. Water. Almost all the processes that make up life on Earth can be broken down into chemical reactions - and most of those reactions require a liquid to break down substances so they can move and interact freely. Liquid water is an essential requirement for life on Earth because it functions as a solvent.What are the 21 elements for life? ›
2. What are the 21 elements essential for life? Calcium, carbon, chlorine, cobalt, copper, fluorine, hydrogen, iodine, iron, magnesium, manganese, molybdenum, nitrogen, oxygen, phosphorus, potassium, selenium, sodium, sulfur, and zinc are regarded as the 21 elements essential for life.What makes us human? ›
The three traits described are bipedalism, language, and tool making. This video assumes some familiarity with the theory of evolution, the process of how organisms developed from earlier forms of life.How many times did life start on Earth? ›
IN 4.5 billion years of Earthly history, life as we know it arose just once.Who were the first human beings on Earth? ›
The First Humans
One of the earliest known humans is Homo habilis, or “handy man,” who lived about 2.4 million to 1.4 million years ago in Eastern and Southern Africa.
Final Answer: Carbon is the most important for the origin of life.What is the chaos theory of life? ›
Chaos theory ultimately teaches that us that uncertainty and unpredictably will always be a constant in life.Does life fight entropy? ›
Then look at what happens: Entropy takes over. Actually, the entire course of our bodies' existence, from birth to death, is spent in a nonstop battle to maintain low entropy. The moment we die, entropy starts increasing as the body's organization gives way to decay. No wonder life is tough.Why is life possible only on Earth? ›
It is the right distance from the Sun, it is protected from harmful solar radiation by its magnetic field, it is kept warm by an insulating atmosphere, and it has the right chemical ingredients for life, including water and carbon.What is the universe made of? ›
The Universe is thought to consist of three types of substance: normal matter, 'dark matter' and 'dark energy'. Normal matter consists of the atoms that make up stars, planets, human beings and every other visible object in the Universe.What was the first year of Earth called? ›
The early Earth is loosely defined as Earth in its first one billion years, or gigayear (Ga, 109y). The “early Earth” encompasses approximately the first gigayear in the evolution of our planet, from its initial formation in the young Solar System at about 4.55 Ga to sometime in the Archean eon at about 3.5 Ga.What are the four key elements of life chemistry? ›
25 chemical elements are essential to life.
Four elements—carbon (C), oxygen (O), hydrogen (H), and nitrogen (N)—make up 96% of living matter.
Some of the most abundant elements in living organisms include carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus. These form the nucleic acids, proteins, carbohydrates, and lipids that are the fundamental components of living matter.What does chemistry mean in love? ›
Chemistry is the emotional connection between two people. This mutual connection can take different forms and may change throughout a relationship, from the first date to the fiftieth anniversary.What are the five spiritual elements? ›
According to some traditions, everything in the universe comes from the five elements: wood, fire, earth, water, and metal.
Scientists believe that about 25 of the known elements are essential to life. Just four of these – carbon (C), oxygen (O), hydrogen (H) and nitrogen (N) – make up about 96% of the human body.What is the most abundant element in the universe? ›
Hydrogen is the most abundant element in the universe, accounting for about 75 percent of its normal matter, and was created in the Big Bang.