Life & Medical Science

Scientists Discovered New Human Cell Structure

We are already aware of the fact that human body consists of millions of cells and we are also familiar with their structure and some of their vital functions. But still there is no stoppage for their evolution and discovery as they are comprising something new within them.

Here is the news that new structure in human cells has been discovered by researchers at Karolinska Institutet in Sweden in collaboration with colleagues in the UK. The structure is a new type of protein complex that the cell uses to attach to its surroundings and proves to play a key part in cell division. The study is published in the journal Nature Cell Biology.

The cells in a tissue are surrounded by a net-like structure called the extracellular matrix. To attach itself to the matrix the cells have receptor molecules on their surfaces, which control the assembly of large protein complexes inside them.

These so-called adhesion complexes connect the outside to the cell interior and also signal to the cell about its immediate environment, which affects its properties and behaviour.

Researchers at Karolinska Institutet have now discovered a new type of adhesion complex with a unique molecular composition that sets it apart from those already known about. The discovery has been made in collaboration with researchers in the UK.

“It’s incredibly surprising that there’s a new cell structure left to discover in 2018,” says principal investigator Staffan Strömblad, professor at the Department of Biosciences and Nutrition, Karolinska Institutet. “The existence of this type of adhesion complex has completely passed us by.”

 

CELL Basics

The cell  is the basic structural, functional, and biological unit of all known living organisms. A cell is the smallest unit of life. Cells are often called the “building blocks of life”. The study of cells is called cell biology.

Cells consist of cytoplasm enclosed within a membrane, which contains many biomolecules such as proteins and nucleic acids. Organisms can be classified as unicellular (consisting of a single cell; including bacteria) or multicellular (including plants and animals). While the number of cells in plants and animals varies from species to species, humans contain more than 10 trillion (1013) cells. Most plant and animal cells are visible only under a microscope, with dimensions between 1 and 100 micrometres.

Origin of the first cell

Stromatolites are left behind by cyanobacteria, also called blue-green algae. They are the oldest known fossils of life on Earth. This one-billion-year-old fossil is from Glacier National Park in the United States.

There are several theories about the origin of small molecules that led to life on the early Earth. They may have been carried to Earth on meteorites (see Murchison meteorite), created at deep-sea vents, or synthesized by lightning in a reducing atmosphere (see Miller–Urey experiment). There is little experimental data defining what the first self-replicating forms were. RNA is thought to be the earliest self-replicating molecule, as it is capable of both storing genetic information and catalyzing chemical reactions (see RNA world hypothesis), but some other entity with the potential to self-replicate could have preceded RNA, such as clay or peptide nucleic acid.

Cells emerged at least 3.5 billion years ago.The current belief is that these cells were heterotrophs. The early cell membranes were probably more simple and permeable than modern ones, with only a single fatty acid chain per lipid. Lipids are known to spontaneously form bilayered vesicles in water, and could have preceded RNA, but the first cell membranes could also have been produced by catalytic RNA, or even have required structural proteins before they could form.

STRUCTURE OF CELL

The cell is like a factory. It is built according to the way it works. Each cell holds many smaller compartments inside, with its own function in coordination with each other.
The cell consists of the outer cell membrane. Cell membrane, sort and organize the contents of the cell into compartments called organelles. This helps the organelles to function more effectively and in a highly specialized manner.
Cell membrane regulates the transportation of the molecules in and out of the cells. The cell membrane is often called as the plasma membrane, because it is the boundary of the cytoplasm.
It is made up of a lipid bilayer with protein molecules embedded in the cell membrane.
The Nucleus is a very important component, that controls all the activities of the cell. It stores DNA, the instruction manual for how to run a cell function.
DNA is surrounded by a double membranous nuclear membrane. Any molecule that requires to move in or out of the nucleus will move through the pores.


In the center of the nucleus is nucleolus, which is responsible in making ribosomal protections and rRNA.
Ribosomes mainly prepare proteins. These are attached to the rough endoplasmic reticulum (ER) and also found floating inside the cytoplasm. This organelle dose not a have membrane.
Endoplasmic Reticulum (ER) transport proteins that are built by the ribosomes and further transferred to golgi apparatus. There are 2 types of ER Rough ER and smooth ER. ER Rough ER and smooth ER are connected to each other. Proteins
Rough ER contains ribosomes on the surfaces. Here the proteins produced by the ribosomes gets modified and is transported.
Smooth ER has little or no ribosomes on the surface. Smooth ER is responsible to make new membranes for the cell or neutralize the toxins.
Golgi apparatus, is an organelle that modifies, sorts, packages and distributes proteins that are received from the ER. Golgi apparatus also prepares materials that are exported outside the cell. The packages prepared by the gogi apparatus are called vesicles.
Vesicles are the membrane packages of enzymes or proteins. The most important vesicles are peroxisome and lysosomes
Peroxisome are the catalyst enzyme filled membrane packages that can neutralize the toxins
Lysosomes are the digestive enzyme filled membrane packages, that are capable of digesting food, virus, bacteria, etc.
In short whole cell is regulated by the nucleus. Within the nucleus contain DNA within. DNA may send the massage out of the nucleus through nuclear pores, into the cytoplasm. Here massage finds the ribosome to build protein and insert that protein into the rough ER. Rough ER sends proteins into new vesicles and these protein filled vesicles are taken up by golgi apparatus. The golgi apparatus modifies, sorts, packages those proteins and built another vesicles. Depending upon the function of the proteins, it will either produce lysosomes, vacuoles, peroxisome or the proteins transported outside the cell.
Mitochondria are another supremely important organelle inside the cell. This dose not have any role in protein production. This is responsible for energy production, metabolism and cell respiration, hence called as a power house. Mitochondria has its own DNA and its own dedicated set of ribosomes within it. So it can be said as a cell within a cell.
Cell structure also contains cytoskeleton, that functions like supporting materials inside the cell. It maintains the shape of the cell and keep organelles intact. There are two types of cytoskeleton, Microfilaments and Microtubules.

Surprising discovery

The newly discovered adhesion complex can provide answers to an as-yet unanswered question – how the cell can remain attached to the matrix during cell division. The previously known adhesion complexes dissolve during the process to allow the cell to divide. But not this new type.

“We’ve shown that this new adhesion complex remains and attaches the cell during cell division,” says Professor Strömblad.

Memory function

The researchers also show that the newly discovered structures control the ability of daughter cells to occupy the right place after cell division. This memory function was interrupted when the researchers blocked the adhesion complex.

The study was done on human cell lines mainly using confocal microscopy and mass spectrometry. Further research is now needed to examine the new adhesion complex in living organisms.

“Our findings raise many new and important questions about the presence and function of these structures,” says Professor Strömblad. “We believe that they’re also involved in other processes than cell division, but this remains to be discovered.”

The researchers call the newly discovered cell structure ‘reticular adhesions’ to reflect their net-like form.

The study was financed with grants from the EU’s Seventh Framework Programme and Horizon 2020, the Swedish Foundation for Strategic Research, the Swedish Research Council, the Swedish Cancer Society and Cancer Research UK.

SOURCE – karolinska

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