The main characteristics of the eukaryotic cell

The eukaryotic cell is the type of cell that makes up animals, plants, fungi, algae, and protozoa. It is more complex than the prokaryotic cell, which is made up of bacteria and archaebacteria.

These are the characteristics that define a eukaryotic cell:

They have a core

The distinguishing feature of any eukaryotic cell is the presence of the nucleus. This is delimited by the nuclear envelope, formed by a double membrane with pores through which cellular components enter and leave.

The nucleus may have one or more nucleoli, a structure composed of ribonucleic acid (RNA) and proteins. This is where the subunits that will be used to attach the ribosomes outside the nucleus are produced.

Some cells may have more than one nucleus. This is the case with some liver cells. The core is usually spherical or rounded. However, there are cells whose nuclei have other forms, such as leukocytes.

Farms of the nuclei of different white blood cells
Nucleus forms in lymphocytes and leukocytes (basophil, eosinophil and neutrophil).

Genetic material

The genetic material of the eukaryotic cell is composed of deoxyribonucleic acid (DNA), a polymer of nucleotides forming two linked chains. It is found mainly in the nucleus. However, there is much smaller DNA in the mitochondria and chloroplast.

All the DNA in a cell is known as the genome. The genome of eukaryotic cells has regions that encode proteins and regions that regulate or control this encoding. In addition, it has mechanisms of protection and repair of DNA to reduce mutations, changes in the sequence of the nucleotide chain.

Its size is measured by the number of nucleotide pairs (also called base pairs). For example, the human genome has more than 3 million base pairs, that of bread yeast. Saccharomyces cerevisiae it has 12,000 base pairs and that of the fruit fly Drosophila melanogaster 137 mil. In human cells, mitochondrial DNA has only 16,000 nucleotide pairs.

The DNA of eukaryotic cells is packaged with proteins called histones, forming chromatin.

nucleus of the eukaryotic cell with DNA
You may also be interested in seeing Eukaryotic Cell and Prokaryotic Cell.

DNA replication

Replication is the synthesis of DNA from a precursor DNA. For this to happen, the DNA develops in areas called “origin of replication”, allowing the entry of DNA-duplicating enzymes.

In eukaryotic cells, DNA replicates only during one phase of the cell cycle, the S phase, or the synthesis phase. In prokaryotic cells this process is carried out continuously. In addition, the genome in the prokaryotic cell has a single source of replication, while the eukaryotic genome has several that may be active at the same time.

At the end of the S phase, the cell has twice as much DNA, which then divides into the M phase, by mitosis.

Cell organization

Eukaryotic cells can live solitary or unicellularly, such as paramecium and amoeba in the Protozoan kingdom and yeasts in the fungal kingdom, or live in association with other cells, attached to each other, forming tissues. such as epithelial cells in the skin.

Multicellular organisms, such as plants and animals, are made up of a variety of eukaryotic cells, which form tissues, organs, and systems.

Form

eukaryotic cells with different shapes
Eukaryotic cells can come in many forms.

Eukaryotic cells can take many forms. For example, amoebas do not have a definite shape because they have the ability to crawl on surfaces, while paramecium and euglena are elongated.

Neurons, cells of the nervous system, have a star shape with extensions protruding from the body of the cell. These extensions are known as dendrites and axons.

Size

The size of eukaryotic cells is very varied. On average it varies between 10 and 60 micrometers (µm). For example, a yeast measures between 3 and 4 µm, the red blood cell between 5 and 10 µm while a neuron can reach 135 µm.

Presence of organelles

Eukaryotic cells are characterized by possessing organelles, which are small organs with specialized functions. These organelles form compartments where the cell can separate the various functions it performs.

For example, in the mitochondria are concentrated the compounds and proteins that are responsible for the process of generating adenosine triphosphate ATP, the energy molecule of the cell. The machinery of photosynthesis is found in the chloroplast of plant eukaryotic cells.

Ribosome

Ribosomes are the protein factories of the cell. They consist of two subunits, one large and one small, each consisting of ribonucleic acid (RNA) and specific proteins.

The ribosome of the eukaryotic cell is larger than that of the prokaryotic cell, although they have the same function. However, the eukaryotic ribosome is less efficient than the prokaryotic one.

In eukaryotic cells, ribosome RNA is synthesized in the nucleolus and then assembled outside the nucleus.

Cell cycle

esque ma of the cell cycle of the eukaryotic cell
Schematic of the phases of the cell cycle of the eukaryotic cell.

The cell cycle is the course that a cell takes from its origin to its reproduction. The eukaryotic cell is characterized by having a four-phase cell cycle:

  1. Phase G1: first phase of growth.
  2. Phase S: ​​DNA is duplicated.
  3. Phase G2: second phase of growth.
  4. Phase M: Mitosis occurs, where the cell divides and gives rise to two new cells.

Aerobic and anaerobic metabolism

Through cellular respiration, the eukaryotic cell transforms glucose into ATP adenosine triphosphate, the energy currency that allows it to perform different functions.

For example, bread yeasts resort to fermentation to metabolize glucose, which does not require oxygen. Liver cells transform sugar into oxygen to produce ATP.

You may also be interested in Aerobic and Anaerobic Breathing

Cell division

Eukaryotic cells can divide by mitosis to form daughter cells with the same genetic information, or by meiosis to produce cells with half the genetic material.

In the process of cell division, the strands of DNA separate and end up in each of the daughter cells in mitosis.

You may also be interested in seeing Mitosis and Meiosis.

Presence of cytoskeleton

The cytoskeleton is a structure of protein threads that intersect in the cytoplasm, forming a kind of intracellular scaffold. In this way the cell maintains its shape and can move.

The cytoskeleton is composed of microtubules, intermediate filaments, or actin filaments.

You may also be interested in viewing Cell Parts.

References

Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., Walter, P. (2008) Molecular Biology of The Cell 5th ed. Garland Science. NY.

Doudna, JA, Rath, VL (2002) Structure and Function of the Eukaryotic Ribosome. Cell 109: 153-156

Geneser, F. (2005) Histology on biomolecular basis. 3ed. Pan American Medical Editorial.

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