What if nucleus is absent in a cell

Sometimes the cell membrane is referred to as the Plasma Membrane. For better understanding, the outer boundary of a cell is known as the plasma membrane. Inside it lies the cytoplasm. Several cellular or cell organelles and inclusions like mitochondria, chloroplasts, etc. Therefore, cell membrane supports and protects the cell. It separates the cell from the external environment. Let us tell you that the cell membrane is present in all the cells. As per the structure of a cell membrane, it is a porous membrane that consists of pores, permit the movement of selective substances in and out of the cell.

Also, it protects the cellular component from damage and leakage. Inside the cell, there is a gel-like fluid known as cytoplasm. It is a medium for chemical reaction and provides a platform so that other organelles can operate within the cell. In the cytoplasm, all the functions of the cell-like expansion, growth, and replication are carried out. Little organs known as cytoplasmic organelles are suspended in the cytoplasm of the cell.

Each organelle type has a definite structure and plays a specific role in the function of the cell. Like mitochondria, ribosomes, endoplasmic reticulum, golgi apparatus, and lysosomes.

The nuclear membrane surrounds the nucleus and inside the nucleus, fluid is present known as nucleoplasm. The control centre of the cell is nothing but a nucleus.

It contains the genetic material of the cell that is DNA. Whereas the nucleolus is a dense region of RNA in the nucleus and is the site of ribosome formation. Or we can say that nucleus contains the hereditary material of the cell DNA. The function of the nucleus is to protect the DNA, it sends signals to the cells to grow, mature, divide, and die. It is also an integral component of a plant's cell structure.

Therefore, it determines how the cell will function as well as the basic structure of the cell. What would happen if nucleus is removed from the cell? The nucleus is known as the control centre of the cell and carries the genetic material. It is the brain of the cell and controls most of its functions.

If the nucleus is removed from the cell then the cell will not be able to function properly, it will not be able to grow. All the metabolic functioning of the cell will stop.

Without nucleus the cell will lose its control. It can not carry out cellular reproduction. Also, the cell will not know what to do and there would be no cell division. Gradually, the cell may die. Or we can say protein synthesis would not be done properly or incorrect proteins would be formed which will result in cell death. As we know that prokaryotes do not have a nucleus and carry out all their functions easily.

That's because all cells are surrounded by a structure called the cell membrane — which, much like the walls of a house, serves as a clear boundary between the cell's internal and external environments. The cell membrane is sometimes also referred to as the plasma membrane. Cell membranes are based on a framework of fat-based molecules called phospholipids , which physically prevent water-loving, or hydrophilic, substances from entering or escaping the cell.

These membranes are also studded with proteins that serve various functions. Some of these proteins act as gatekeepers, determining what substances can and cannot cross the membrane. Others function as markers, identifying the cell as part of the same organism or as foreign.

Still others work like fasteners, binding cells together so they can function as a unit. Yet other membrane proteins serve as communicators, sending and receiving signals from neighboring cells and the environment — whether friendly or alarming Figure 1.

Within this membrane, a cell's interior environment is water based. Called cytoplasm , this liquid environment is packed full of cellular machinery and structural elements. In fact, the concentrations of proteins inside a cell far outnumber those on the outside — whether the outside is ocean water as in the case of a single-celled alga or blood serum as in the case of a red blood cell.

Although cell membranes form natural barriers in watery environments, a cell must nonetheless expend quite a bit of energy to maintain the high concentrations of intracellular constituents necessary for its survival.

Indeed, cells may use as much as 30 percent of their energy just to maintain the composition of their cytoplasm. As previously mentioned, a cell's cytoplasm is home to numerous functional and structural elements. These elements exist in the form of molecules and organelles — picture them as the tools, appliances, and inner rooms of the cell. Major classes of intracellular organic molecules include nucleic acids, proteins, carbohydrates, and lipids, all of which are essential to the cell's functions.

Nucleic acids are the molecules that contain and help express a cell's genetic code. DNA is the molecule that contains all of the information required to build and maintain the cell; RNA has several roles associated with expression of the information stored in DNA.

Of course, nucleic acids alone aren't responsible for the preservation and expression of genetic material: Cells also use proteins to help replicate the genome and accomplish the profound structural changes that underlie cell division. Proteins are a second type of intracellular organic molecule.

These substances are made from chains of smaller molecules called amino acids , and they serve a variety of functions in the cell, both catalytic and structural. For example, proteins called enzymes convert cellular molecules whether proteins, carbohydrates, lipids, or nucleic acids into other forms that might help a cell meet its energy needs, build support structures, or pump out wastes.

Carbohydrates , the starches and sugars in cells, are another important type of organic molecule. Simple carbohydrates are used for the cell's immediate energy demands, whereas complex carbohydrates serve as intracellular energy stores. Complex carbohydrates are also found on a cell's surface, where they play a crucial role in cell recognition. Finally, lipids or fat molecules are components of cell membranes — both the plasma membrane and various intracellular membranes.

They are also involved in energy storage, as well as relaying signals within cells and from the bloodstream to a cell's interior Figure 2. Some cells also feature orderly arrangements of molecules called organelles. Similar to the rooms in a house, these structures are partitioned off from the rest of a cell's interior by their own intracellular membrane.

Organelles contain highly technical equipment required for specific jobs within the cell. One example is the mitochondrion — commonly known as the cell's "power plant" — which is the organelle that holds and maintains the machinery involved in energy-producing chemical reactions Figure 3. See how cells compare along a relative scale axis with other molecules, tissues, and biological structures blue arrow at bottom.

Figure Detail. Rather than grouping cells by their size or shape, scientists typically categorize them by how their genetic material is packaged.

If the DNA within a cell is not separated from the cytoplasm, then that cell is a prokaryote. All known prokaryotes, such as bacteria and archaea , are single cells. In contrast, if the DNA is partitioned off in its own membrane-bound room called the nucleus , then that cell is a eukaryote. Some eukaryotes, like amoebae, are free-living, single-celled entities. Other eukaryotic cells are part of multicellular organisms. For instance, all plants and animals are made of eukaryotic cells — sometimes even trillions of them Figure 4.

Figure 4: Comparing basic eukaryotic and prokaryotic differences A eukaryotic cell left has membrane-enclosed DNA, which forms a structure called the nucleus located at center of the eukaryotic cell; note the purple DNA enclosed in the pink nucleus.

A typical eukaryotic cell also has additional membrane-bound organelles of varying shapes and sizes. In contrast, a prokaryotic cell right does not have membrane-bound DNA and also lacks other membrane-bound organelles as well.

Researchers hypothesize that all organisms on Earth today originated from a single cell that existed some 3. This original cell was likely little more than a sac of small organic molecules and RNA-like material that had both informational and catalytic functions. Over time, the more stable DNA molecule evolved to take over the information storage function, whereas proteins , with a greater variety of structures than nucleic acids, took over the catalytic functions.

As described in the previous section, the absence or presence of a nucleus — and indeed, of all membrane-bound organelles — is important enough to be a defining feature by which cells are categorized as either prokaryotes or eukaryotes. Scientists believe that the appearance of self-contained nuclei and other organelles represents a major advance in the evolution of cells. But where did these structures come from? More than one billion years ago, some cells "ate" by engulfing objects that floated in the liquid environment in which they existed.

Then, according to some theories of cellular evolution , one of the early eukaryotic cells engulfed a prokaryote, and together the two cells formed a symbiotic relationship. In particular, the engulfed cell began to function as an organelle within the larger eukaryotic cell that consumed it. Both chloroplasts and mitochondria, which exist in modern eukaryotic cells and still retain their own genomes, are thought to have arisen in this manner Figure 5.

Figure 5: The origin of mitochondria and chloroplasts Mitochondria and chloroplasts likely evolved from engulfed prokaryotes that once lived as independent organisms. At some point, a eukaryotic cell engulfed an aerobic prokaryote, which then formed an endosymbiotic relationship with the host eukaryote, gradually developing into a mitochondrion. Eukaryotic cells containing mitochondria then engulfed photosynthetic prokaryotes, which evolved to become specialized chloroplast organelles.

Of course, prokaryotic cells have continued to evolve as well. Different species of bacteria and archaea have adapted to specific environments, and these prokaryotes not only survive but thrive without having their genetic material in its own compartment. For example, certain bacterial species that live in thermal vents along the ocean floor can withstand higher temperatures than any other organisms on Earth.

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