A cell is the smallest part of an organism capable of carrying out life processes on its own. It is from the union of two cells, i.e. a sperm and an egg, that the human body is created. When it matures, it will no longer be possible to precisely determine how many different cells it is made of. How are cells built and how do they work?

The smallest part of our body iscell . It's just thatthe structure of the human body's cellmay be different depending on what role it is supposed to play. A typical one is filled with a thick liquid called the cytoplasm in which the nucleus is embedded. The cytoplasm and nucleus are surrounded by a thin membrane. However, not all cells look the same. They differ in structure, functions and size. However, they all reproduce by division. As a rule, they are not randomly mixed together, but form groups called tissues.

The nucleus occupies the central part of almost every cell. It is like a ball suspended in the cytoplasm, surrounded by a porous membrane. The interior of the nucleus is filled with organic compounds, mainly proteins, forming a semi-liquid karyoplasm. This rare jelly includes, among others deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) molecules. DNA molecules resemble two strands twisted in a spiral. They contain billions of information about the structure and operation of our body. It is a genetic code by which cells can reproduce and take over certain functions. It's like a human matrix. RNA, in turn, contains coded information about the production of specific proteins from which our body is made.

The plasma membrane protects the cell

This surrounding cell is called the plasma membrane. It has three layers: the middle one is made of lipids, or fats, and the other two are made of proteins. The plasma membrane is strong but slightly porous. It allows substances necessary for its life and development to enter the cell, and to the outside releases, for example, hormones.

Some cells (e.g. white blood cells, or leukocytes) use their membranes to fight the body's enemies, e.g. bacteria. When it touches the bacteria, the membrane delves and locks the intruder in a special bubble (vacuole). In the vacuole, cellular enzymes digest, that is, destroy the bacteria. Professionally, this process is called phagocytosis.

Important

What is the difference between individual cells?

Hundreds of cells cooperate with each other in the human body, often significantly different in structure:

  • some (e.g. skin and blood cells) live for a few weeks at most, while others (e.g. nerve and bone cells) may live as long as we do
  • striated or skeletal muscle cells have several nuclei, while erythrocytes, or red blood cells, do not have any
  • only nerve cells are equipped with projections, thanks to which they communicate with each other and with other, distant organs

The structure of the interior of the cell

The transparent, jelly-like liquid that fills the cell is the cytoplasm. The so-called organelles. It can be said that these are the internal organs of the cell. If we compare a cell to a factory, the organelles are its individual departments. Everyone does something else, but they work together to keep the cell alive. The number and type of organelles depend on the function of the cell.

The cytoplasm is divided into parts by membranes that form a network of irregular tubules and vesicles. This system is called the endoplasmic reticulum. In some places, corpuscles called ribosomes are attached to the reticulum. They belong to the smallest organelles. They produce proteins that go beyond the cell and are used by the entire body. Ribosomes not attached to the reticulum, the so-called free, they produce proteins for the use of the cell itself.

The so-called agranular (smooth) reticulum with no ribosomes. In the smooth reticulum, e.g. in the liver cells, the metabolism of lipids (fats) and cholesterol takes place, and in the cells of the testes, ovaries and adrenal glands the production of steroid hormones.

The Golgi apparatus is formed from part of the smooth reticulum. It looks like a pile of plates stacked on top of each other. Vesicles surrounded by a membrane detach from its shores. The vesicles travel to the cell membrane, connect with it, then open and throw their contents out of the cell. This content is made up of various substances that are produced by the cell for the benefit of the body. For example, in the cells of the pancreas, there is a zymogen in vesicles that detach from the Golgi apparatus. When the follicle reaches the cell membrane, it ruptures and releases the zymogen, it turns into a digestive enzyme. So the Golgi apparatus is like a courier, which packs and transports substances produced by it to the outside of the cell.

Mobile: energy and enzyme factory

The organelles scattered in the cytoplasm also include mitochondria. They look like mini-cucumbers. There are up to several hundred of them in one cell.They are surrounded by two membranes and filled with a liquid, the so-called a matrix. Mitochondria are the centers of cellular respiration. With the participation of many enzymes in the mitochondria, nutrients are converted into energy. It serves to support the life of the cell and to enable it to work. Thus, mitochondria are the power plant that supplies energy. When a cell needs a lot of fuel, they grow and divide to meet the demands. The interesting thing is that they have their own DNA independent of that of the nucleus.

Lysosomes are also organelles. They are somewhat like mitochondria, but surrounded by a single membrane. Lysosomes contain enzymes that digest, among others, damaged organelles and bacteria closed in vacuoles. When a cell dies, lysosomal enzymes are released and digested as well. This process is called autolysis.

Important

Stem cells

At a very early stage of embryonic development, all cells in our body look the same. Each of them can develop any specialized cell that will be used to build an organ, e.g. heart, liver, skin. The impulse from the genetic code and the mutual influence of cells make an undifferentiated cell, or a parent cell, begin to develop as, for example, a fat or a muscle cell. However, a certain pool of cells that the body will need to regenerate tissues in the future remains undifferentiated. We have such cells, for example, in the bone marrow. They are a source of renewal for red cells (erythrocytes) that only live about 100 days.

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Genetic diseases