The cell is the smallest metabolic unit of living beings, that is, it is the smallest unit of life.
Even alone, it forms a complete living being such as, for example, bacteria and protozoa, unicellular organisms. When in groups they form multicellular organisms, such as: plants, animals, etc.
The cell has all the necessary material to carry out vital processes such as nutrition, energy release and reproduction.
The human being is made up of about 100 trillion cells, the egg being the largest of them, it has approximately the diameter of a full stop.
Cell Structure
The cells that make up most living beings have a membrane surrounding their DNA, for this reason they are called eukaryotic cells . A eukaryotic cell is made up of a plasma membrane, cytoplasm, and nucleus.
Unlike eukaryotic cells, prokaryotic cells do not have a nuclear membrane or membranous organelles inside.
The plasma membrane is a kind of film that surrounds and protects the cell. It has selective permeability, that is, it regulates the entry and exit of substances from the cell.
Through the membrane the cell receives oxygen and nutrients and eliminates carbon dioxide and other substances.
In the plant cell , in addition to the cell membrane, there is, more externally, the cell wall , made of cellulose .
The cytoplasm is the part of the cell that lies between the cell membrane and the nucleus and is made up of a gelatinous material called hyaloplasm .
It is formed by water, mineral salts, proteins and sugars. In the hyaloplasm, there are several organelles, structures responsible for various cellular activities, such as: nutrition, respiration, storage of substances, etc. Together, they are responsible for sustaining life.
Among the organelles are:
- Mitochondria: energy plant of cells. They carry out cellular respiration and release the energy necessary for the cell to perform its functions;
- Ribosomes: manufacture proteins in cells. Non-membranous organelles fundamental to cell growth and regeneration;
- Endoplasmic reticulum: network of channels and recesses where proteins, fats, mineral salts, etc. circulate;
- Golgi complex: formed by small flattened pockets. It produces certain “sugars”, modifies and stores proteins and other substances. It also produces lysosomes;
- Lysosomes: carry out digestion inside the cell;
- Centrioles: small cylindrical structures that participate in cell division;
- Vacuoles: small sacs that store or transport enzymes, water, etc.;
- Chloroplasts: organelles present only in plant cells, responsible for photosynthesis.
The nucleus is the command center of cellular activities, in general, it is located in the center of the cell and is surrounded by a nuclear membrane called a nuclear membrane.
Inside the nucleus are the chromosomes , which hold the cell’s genetic material ( DNA ). Chromosomes are immersed in karyolymph or nuclear juice, gelatinous material that fills the space inside the nucleus.
