The human body has billions of cells. These are small building blocks that are responsible for maintaining and building tissue and organs. In order for cells to maintain, divide or destroy themselves, a cell cycle takes place. The cell cycle in the organism consists of cell growth and division.
Cell growth refers to the increase in size and volume of all individual cells. It is genetically controlled and takes place before and between cell division. The prerequisite is the cellular metabolism, also called metabolism, whereby the cells process nutrient molecules.
What is cell growth?
In a living organism, cells are constantly dying. In humans there are several hundred million cells, the loss of which makes the formation of a new cell necessary. If the cell arises again, cell division occurs. For this, signal cascades, messenger substances and hormones are necessary, which also cause cell growth.
When a single cell grows, the process is extremely complex. When a bacterial cell grows, z. B.about two thousand chemical reactions take place at once. These are u. a. Energy release processes, biosynthesis of small molecules to bind macromolecules, or polymerization reactions. All cellular structures are formed during cell growth, including the cell walls, ribosomes or flagella.
Function & task
During cell growth, each additional cell receives a complete chromosome and thus sufficient information about all monomers, ions and macromolecules for another independent cell to exist.
Multicellular organisms in turn grow by multiplying these self-formed cells. Cells need stimuli to multiply. That can be B. be growth hormones.
Until the first division of a cell begins, cell growth always takes place. The time cycle of cell growth depends on genetic factors and on the environment. The functions of the cells and the activity of the genes are controlled by genetic circuits and also influence the effects of growth.
Different speeds in cell growth can, for. B. in microorganisms lead to certain processes taking place more slowly. At the same time, there is also natural selection that favors cells that grow faster than others.
Cell growth is also differentiated once again in the cycle that takes place in the organism and in the creation of cell cultures.
While bacteria, for example, can divide again after just twenty minutes, the period for a human cell and its division is a little over ten hours.
The growth of a cell is calculated in terms of surface area to volume. Due to this ratio, the cell soon no longer has enough surface area to remove enough pollutants and absorb nutrients. Therefore their growth is limited, both in single cells and in the development of multicellular cells.
Cell growth takes place in the body to a limited extent, but is also operated as a cell culture. In this regard, cells are multiplied and reused at a certain stage, e.g. B. for various experiments to study diseases.
A single cell has an individual cell age, which begins after mitosis and reaches a maximum value at the next division, which corresponds to the doubling time. The division of one into two, two into four, and so on is called exponential or infinite growth.
Certain nutrients and minerals are important for cell growth, including potassium. This regulates cell growth, which in turn maintains the balance of acids and bases in the body and the release of hormones.
Basically, cells produce proteins that regulate cell growth and also affect genes. The cell growth also determines the better evaluation of the genes.
Changes in a cell affect the concentration of the proteins produced. Fast-growing cells have more polymerases that allow genes to be transcribed. Nevertheless, the fact that the activity of genes depends on cell growth makes it difficult to measure genetic circuits. The parameters that characterize the activity of genes depend on the protein concentration and the growth rate. The growth rate is understood to mean the increase in a size over a certain period of time. It is calculated by the growth factor.
Illnesses & ailments
Cell growth is of particular interest in oncology, whose research is focused on the growth of cancer cells. In addition to cell growth, the number of cells also plays an important role.
If the genome of a cell is disturbed, it can change pathologically. With a small number of such cells, the body's own defense system reacts with destruction or renewal. Only when cells of this type grow and divide in an uncontrolled manner do benign or malignant growths, known as tumors, form.
With a malignant tumor, the tissue boundary is soon exceeded by growth. The surrounding tissue is destroyed and new tumors are formed. The cancer cells behave like normal cells in this process. They don't know when to stop dividing or when to die. Likewise, they do not adhere tightly to one another, so that they can separate from their cell structure and migrate. In this way, they can then continue to grow elsewhere. This is then a metastasis.
In turn, if the tumor cells continue to grow, they will soon form their own blood vessels to receive oxygen, hormones, and glucose. This allows the tumor to penetrate the surrounding tissue.
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