Single Cell to Trillions – Cellular Structuring of Life…
Nothing can be more fascinating to explore than the elusive idea – the origin of life on this beautiful planet called Earth. We continue to wonder. How exactly life started? It still remains the most sought after mystery. Though just few days back only we managed to capture the mystical picture of the Black Hole. And this happened billions of year back. The mystery still continue to stay so. Though we have erudite theories and counter theories, we have scientifically established hypotheses but nothing can ascertain with full certainty…the origin of life.
The Big Bang Theory.
The Deep Sea Vent Theory.
And the quintessential question that keep nagging us, why life form choose this lovely blue planet to make its home. Why on Universe the planet Earth? It’s all part of the magical mystery of universe. That keeps us in awe and wonder. There are billions of galaxies and planets that are home to this wonderful world of universe. Nobody can say with conviction how the beginning was all about.
Was it sudden or it evolved gradually?
And hence we have so many theories that attempts to offer some plausible answers. Perhaps nothing definitive. We have these series of profound questions that keep perennially haunting us. After all we human beings are innately a curious creäture. The question keeps ticking. It is largely presumed that life forms came into existence some 3.5 billion years back.
The number is mind boggling…
Anybody’s presumption on the number game though greatly supported by the fossils records stored in the layers of rock. The oldest known fossils are around 3.5 billions years old. The Earth itself is assumed to be around 4.5 billions years old. We are mostly assuming life formed on earth alone. As there is no signs of life form discovered in any other planet…that’s because we have not yet explored beyond few known galaxies.
There are billions of them…
Life may have formed somewhere else in the universe and later stayed on this planet. Life still may be continuing in those distant galaxies and distinct planets. We talk of aliens. We are so excited to hear any rumored news on space invader. It keeps coming. There are theories stating that we are nothing but star-dust. We came into being through the touch of cosmic power and that power came in the form of stars. There were some stars in the form of meteorites traveled the cosmic distance and landed on planet earth.
Perhaps it was destined…
Along with those star-dust, arrived the tiny particles of life form. The organic compounds as seeds to germinate life on this fertile planet called as Earth. Everything was in dark and it was a world of wild guess and mild press did throw some light into those gray zones of darkness. Until 300 years back, as part of a very recent history compared to the billions of year’s history of the universe, it was the evolutionary theories of species proposed by the great biologist and naturalist Charles Darwin. All life has evolved from a simple common ancestor. All life forms followed the process of natural selection. In 1857 Darwin published the theories in his path breaking book titled “On the Origin of Species”. Though this book never said anything about how the first organism came into being in this world.
Life needed water, air and sun light to sun shine. How did water first come into existence? Did water existed on this planet or came from some other planet and where did the first molecule of water formulated into its tangible form. Did air existence in our environment or how did air came into its functional form. How did sun come in existence and how it continues to churn out energy for billions of years? These all elements joined in the perfect proportion one fine day and formed the first organic molecule. This molecule kept evolving and resulting in more complex form from a single cell to this whole body of trillions of cells.
All cells store their energy in the same molecule called as Adenosine Triphosphate (ATP). When cell needs energy they break the third phosphate and turn the ATP into ADP, in the process releases the energy.
It was the famous Miller-Urey experiment conducted in 1952 where he circulated four chemical elements believed to have present at the early part of earth formation in a set of glass flasks. The four chemicals were water, hydrogen, ammonia and methane. He subjected this composition to electric shock representing the lightning strike that would have been then the common occurrence on earth. On analyzing the mixture he found that it comprised two amino acids which is building block of any life form. Proteins one of the four fundamental macro molecule that make our body structure comprised of amino acids.
Life is based on carbon. It is part of everything in our body. This is because carbon has the ability to form bond with four atoms simultaneously thereby making it potent to form long chain of molecules. The two most fundamental building block of life is protein and nucleic acids. These are long chain molecules. Proteins are made of amino acids. Nucleic acids are made of nucleotide. The question remains whether there can be non-carbon based life, as on earth every life form is carbon based structure and system.
Though later it was discovered that the mixture of gases were different than these four. Life is more complex and the process of locating the genesis is much more complicated than it was generally presumed. Life is not just a bunch of chemicals but there is mechanics to it and life is complex body of machines. DNA carries the genes. The genes come from the ancestral bacterium. How cells copy their DNA. And how parents make copies of their genes and pass onto their offspring.
DNA tells cell how to make proteins. It is protein that helps form the body structure in its proper form. Protein is a long chain of amino acids in a specific order and it is this order that makes all the difference. RNA is a copy of the DNA. The process of converting that piece of information in RNA into a protein goes on in every cell. In order to understand the origin of life we need to decipher the secret behind the genesis of DNA, RNA and protein. Also how they started to learn to work together and this working became the basis of the existence of life.
Life is indeed a complex structure.
This very organic structure is composed of a set of elements and molecules. There are almost 60 odd elements found in our body structure. All are not equally important and these have there relative strength and positioning in our body formation. Scientists believe that around 25 of these elements are essential to our life. Just four numbers namely oxygen, carbon, hydrogen and nitrogen comprise of 96% of total elements. These all elements are there in abundance in nature. We source these elements from nature to nurture of our body structure. This entire human body formation from few sperm cells into the most complex structure on universe is the fascinating study of science. Doctors to biologists have done extensive dissection to decipher the design behind the structure of life. Still scientists are unable to design a life form by taking this set of molecules and combining into a body structure.
How the first living thing on Earth did came into existence?
The single celled micro organism or microbes as we refer to. It is once again presumed that cell membrane known as prokaryotes and eukaryotes appeared almost 4 billion years back. The prokaryotes lack cell nucleus and membrane. On the other hand the eukaryotes cell comprises of a nucleus and surrounded by a membrane.
How did inanimate things changed from an animated living thing? How did these non living became living thing on this planet? How did this complex organic function kept evolved and managed to reach a state of living form in action. It is the formation of the fully formed complex human body structure with life. Biogenesis is the study of life from organic cells. On the other hand abiogenesis the study of life from the inorganic cells or non living matter.
Every living thing is descended form a bacterium. And all living beings are made of cells. Cells are the basic building blocks of all living beings. Human body is composed of trillions of cells. To be little more precise there are 37.2 trillion cells in our body. The cells add up make tissues and tissues working together to make up organs. The organs from heart to liver to kidney constitute the bigger blocks of human body structure. Cells have many individual parts and each has different function to perform. These are called as organelles. All these cellular organelles are made of four macro molecules. All these macro molecules are made of atoms and there smaller building blocks than atoms and are known as quarks. For instance Mitochondria are that part of cell that converts energy from food into a form that cell can use. Similarly, Ribosomes are that part of cell that processes the genetic instructions to create proteins.
All life is composed four macro molecules namely carbohydrates, lipids, proteins and nucleic acids. Each cell contains DNA which is the basic code that tells each cell how to function and grow. The study of cell is called as Cell Biology.
Cells were discovered in the 17th century and only when the first modern microscope was invented. Cells are a squashy orb with a sturdy outer wall known as membrane. The function of cell is to be keeping in place all essential ingredients of life. The essence of cell grew in size and stature only when it encompassed the genes that can pass onto their offspring.
Life science revolves around the chemistry and biology of cells. Everything has changed with discovery of cell and we are merely a compounded product of cellular structure.
Nihar R Pradhan