About central dogma in biology

Central dogma in biology dates back to 1958, when F. Crick proposed a theory that explained the flow of information within the organism. Moreover, it can be represented in the form of the flow diagram, as you can see right here in the picture, which I borrowed from the book Genetic engineering - dreams and nightmares. The information flow starts from nucleic acids, which are building rocks of DNA, our genetic code. That's all in the nucleus of basically every cell.

 

In there, DNA strand is split apart, and one strand leaves nucleus as messanger RNA, or mRNA. This molecule carries information about how to make various proteins needed for the body. So out of nucleus, and in the cytoplasm, mRNA is processesed and used for protein synthesis.

 

Protein synthesis comes in four structural steps called primary, secondary, tertiary, and quaternary structures. Primary structure consists of the chain of amino acids, and secondary is already building blocks like alpha-helixes or beta-pleated sheets. Those are then used in numerous combinations to create many different proteins. Those are then transported out of the cell into the place where it will be used for building or regenerating the new or existing tissue. And that's how the organism is built up.

 

 

DISCOVERY OF REVERSE TRANSCRIPTASE

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Now we get to the point where this dogma becomes a dogma.This way of information flow was thought to be not revearsable, or simply put, it's only one-way street. But the scientific research and fast progress in genetic engineering proved that the opposite way is also possible. Study of retroviruses like Rous sarcoma virus, or bacteria like Escherichia coli (E. coli), showed that those micro-organisms contain an enzyme, which is able to create brand new DNA code. This enzyme is called reverse transcriptase.

 

In order to do this, it first creates so called complimentary DNA, or shortly cDNA. This is then compared with mRNA, because this serves as a template for reverse transcriptase. Here is where evolution and natural selection will play a part for a while, and the end/best result is then doubled and twisted by DNA polymerase - another enzyme. Well, and the new DNA is ready.

 

The research on viruses and bacteria has been proved to be very beneficial in many ways. For example many enzymes and hormones can be synthetically produced in laboratories using bacteria or viruses. This has been a huge relief from getting all those needed substances by natural ways, that is from people. Pharmacology experienced a big boom since, and is still evolving and developing, along with genetic engineering, as one of the leading research programs to date.    

Introduction

Hello everyone who is into any information about the human body. Be it a biochemistry, human biology, or physiology, flow diagrams are here to interpret some very complex information flow within our bodies in the simplest possible terms. As the saying goes, seeing once is better than hearing a hundred times, I found flow diagrams very useful tools for remembering things I want to remember, and understand the thing I want to understand.

 

Because human body is so complex and delicate at the same time, informations about it could be seen as layered into many dimensions. So many flow diagrams are here trying to reflect as many of those dimensions working together, and plus present the picture that shows links between them. For example, some flow diagrams are purely about endocrine system (or hormones), some purely about nervous system (or nerves). But some are about interconnected cooperation of those systems, and that's where it starts to be interesting.

 

Seeing a bigger picture is very important, as it gives a many ideas about connections between different parts of body. So here in this blog, I'll try to collect and comment many of those flow diagrams I found across various literature and internet. This blog is the result of my dedication to pursuing the understanding of many complex processes that are happening inside us. I only hope that you will find useful my explanations along with those diagrams. I'll try go as simple as possible, as the basics are usually most important, so every new or seemingly complicated term will be explained in simple laymen terms.

So how would you translate for your self the human body flow diagram mania? It doesn't have to be necessarily a set of flow diagrams about human body, like you found plenty in biochemistry books. But rather see it as a collection of diagrams concerning human body, which represents flow of molecules, substances, time, energy, information (you name it) in the human body. As I said, the bigger picture must be seen, and that's my motto, so here is the flow diagram to illustrate my point.

 



 This flow diagram basically represents the biggest picture possible. The ultimate structure of reality or the existence, mainly on the planet earth, but possibly not only here. Technically, all is composed with very small parts called atoms, even if those has its component too - protons, neutrons, and electrons. Either two or more atoms put together create so-called inorganic molecules, or commonly called inorganic compounds.

 

By the definition, those are very small, with very simple structure, and not containing the carbon atom. The only two exceptions are carbon dioxide, and bicarbonate ion, which contain carbon, but are still classified as inorganic - mainly due to simple structure. Other examples are water, salts, bases, acids, and separate ions called electrolytes. In the body, there's about 55-60% water, and 1-2% of all other inorganic molecules.

 

Once a lots of those are put together, the organic molecule is created. Those are big, complex, and contain carbon, or a lots of carbon atoms. The resting 40% of the body is built with those organic molecules. Types of those are carbohydrates, lipids, proteins, nucleic acids (building blocks of DNA), and ATP - the energy molecule of the body.

 

So once those already big and complex organic compounds (or molecules) start to react with each other, even bigger molecules are created. If big enough to start fulfilling some particular function, they become an organelles - like mitochondria, nucleus, ribosome, lysosome, plasma membranes, centrosomes, etc, etc. Those are the functional parts of the cells, the building units of every living organism.

 

On cellular level there is about 200 different types of cells in the body. Those close to each other, and with similar (or the same) function group together and make a functional unit called the tissue. Different tissues which are working on the same basic function create an organ, and different organs working on the same basic function create a system.

 

Altogether 12 systems in the body make the whole organism, in our case, the human body. Two basic types of body (male and female) can create a so-called breeding pair, and bring about another organism into the existence. This way populations are created leading to represent certain species, differenciating themselves from many other species on the planet. So that would be the flow diagram above put into the words.

 

Levels of structural organization

 

Still there is a number of dimensions within an organism, or human body, which I'd like to list nicely from the smallest to the biggest:

 

1. chemical level - atoms and molecules (e.g. water, oxygen, protein, ...)

2. cellular level - different types of cells (nerve, sperm, muscle, goblet, ...)

3. tissue level - different types of tissues (adipose, bone, connective, ...)

4. organ level - different types of organs (heart, brain, kidney, spleen, ...)

5. system level - 12 different systems (skeletal, digestive, urinary, ...)

6. organismal level - whole human body, or some other organism