What are Eukaryotic Cells?

One of the two types of cells is a eukaryotic cell. "Eukaryotes" are organisms made up of eukaryotic cells, which include plants, mammals, fungi, and protists. The only species that do not have a prokaryotic cell structure are those that are based on a eukaryotic cell. 

 

These species are located in the Bacteria and Archaea domains. You may fully comprehend what makes a cell eukaryotic by understanding the differences between eukaryotic and prokaryotic cells.

 

How do Eukaryotic Cells Work?

 

Eukaryotic cells are characterized by their structured nucleus and organelles that are encased in membranes. Animals, fungi, protists, and plants are eukaryotic cells examples. They have chromosomes, which organize their genetic material. Eukaryotic cells have the Golgi apparatus, mitochondria, ribosomes, and nucleus. Let's take a closer look at the components of eukaryotic cells.

 

The biological origin of Eukaryotic cells

 

The early eukaryotic cells that coexisted symbiotically with the earliest prokaryotic cells are thought to have given rise to the eukaryotes, according to the Endosymbiotic theory. They might have shared a common ancestor with a microbe that contained an early prokaryotic cell. 

 

The prokaryotic cell eventually developed into a subcellular component (organelle) of the eukaryotic cell as a result of the two cells' endosymbiosis throughout time. Prokaryotes that are photosynthetic evolved into chloroplasts, whereas some of them became the mitochondria we see today. 

 

Soon after, these early eukaryotic cells split into various taxonomic kingdoms (such as Animalia, Plantae, Protista, and Fungi), each of which has unique traits that set it apart from the others.

 

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Characteristics of Eukaryotic Cells

 

Organelles found in eukaryotic cells perform a range of tasks within the cell (described in detail, below). The cytoskeleton, which is also important in relaying signals from one area of the cell to another, stabilizes and physically supports each organelle. 

 

Microtubules, microfilaments, and intermediate filaments make up the majority of the cytoskeleton in eukaryotic cells. Cytosol is the name given to the liquid that covers every cell organelle.

 

The structure of a eukaryotic cell is depicted in the figure below. A cell from an animal. Organelles, including the nucleus, are displayed. The blue material encircling the organelles is the cytosol. The cytoplasm is the collective name for the cytosol and all organelles other than the nucleus.

 

Features of Eukaryotic Cells

 

Each membrane-bound structure performs a particular biological function within a eukaryotic cell. Below is a summary of some of the basic elements found in eukaryotic cells.

 

1. Nucleus: The nucleus stores the genetic information in chromatin form.

 

2. Nucleons: The eukaryotic cell's nucleolus, which is located inside the nucleus, is where ribosomal RNA is made.

 

3. Plasma membrane: The plasma membrane is a phospholipid bilayer that encloses all of the cell's organelles and surrounds the whole cell.

 

4. Cell wall or cytoskeleton: The cell wall or cytoskeleton gives cells structure, permits cell mobility, and participates in cell division.

 

5. Ribosomes: Ribosomes are in charge of producing proteins.

 

6. Mitochondria: Mitochondria, also referred to as the cell's powerhouses, are in charge of generating energy.

 

7. Cytoplasm: The area of a cell between the nuclear envelope and the plasma membrane is known as the cytoplasm.

 

8. Cytosol: Organelles are found inside a gel-like substance called cytosol, which makes up cells.

 

9. Endoplasmic reticulum: This organelle is responsible for the maturation and transit of proteins.

 

10. Vesicles and vacuoles: Vesicles and vacuoles are membrane-bound sacs used for both storage and movement.

 

The Golgi apparatus, chloroplasts, and lysosomes are further typical eukaryotic organelles that are present in many, but not all, of them.

 

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The Structure and Purpose of Eukaryotic Cells

 

One of the distinguishing features of eukaryotic cells is the existence of a nucleus. Large organelles like the nucleus are frequently the most noticeable part of an eukaryotic cell. See the illustration of an eukaryotic cell below. 

 

Eukaryotic cells do not all have nuclei. Mammalian red blood cells, for instance, lose their nucleus when they reach adulthood in order to boost their affinity for breathing gasses. In contrast to nucleated cells, which have a nucleus, anucleate eukaryotic cells do not have a nucleus. 

 

The nucleus serves as the central nervous system of eukaryotic cells. It has the chromosomes (nuclear DNA) that house the majority of a eukaryote's genes. The nucleus DNA contains the genetic code that the cell uses to control its differentiation, development, homeostasis, reproduction, heredity, and death.

 

A nuclear envelope surrounds the genetic material and the other elements of the nucleus. The bilayer lipid layer that makes up this envelope divides the cytoplasm from the nuclear components. However, it is pierced with holes to allow some molecules to travel back and forth. 

 

For example, after copying the genetic code from the nuclear DNA, mRNA leaves the nucleus and transports it to the ribosome linked to the endoplasmic reticulum for protein synthesis. Ribosomes are found in cells other than eukaryotic cells. They exist in prokaryotic cells as well. However, eukaryotic cells' ribosomes, or 80S, are bigger than prokaryotic cells' ribosomes, or 70S.

 

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Life Cycle of Eukaryotic Cells

 

A cell's life cycle is known as the cell cycle. This cycle involves its growth and division. All stages have checkpoints so that proteins can assess whether the cell is prepared to start the subsequent stage of the cycle.

 

1. Quiescence (G0)

 

A phase in which the cell is not actively dividing is referred to as quiescence, sometimes known as senescence or resting. It's sometimes referred to as Gap 0 or G0. Although cells can reach this stage and then cease dividing indefinitely, which would put an end to the cell cycle, it is nevertheless regarded as the beginning of the cell cycle. 

 

Cells in the neurological system, liver, stomach, and kidney are a few examples of tissues in which they might progress to this stage and stay there for extended periods of time. Additionally, it might happen if a cell's DNA is harmed. While an organism is alive, most cells do not enter the G0 stage at all and can continue to divide indefinitely.

 

2. Interphase

 

The cell develops and absorbs nutrients during interphase as it gets ready to divide. The majority of the cell cycle is spent in the interphase. There are three sections to it: Gap 1, Synthesis, and Gap Growth Phase. A growth phase is often referred to as Gap 1 (G1). The cell grows in size and accumulates more proteins as well as organelles like the energy-producing mitochondria. 

 

DNA replication takes place during the synthesis (S) phase. Each chromosome is made up of two sister chromatids after the chromosomes duplicate during synthesis. The amount of DNA in the cell has doubled by the time this stage is over.

 

G2 is a different growth phase. In preparation for mitotic division, the cell enlarges even more, and the remaining organelles are replicated.

 

The M phase, also known as mitosis, is when a cell starts to arrange its duplicated DNA in preparation for division into two daughter cells. One of each chromosome is transferred into each daughter cell as a result of chromosomal separation. As a result, the daughter cells inherit the parent cell's chromosomes. 

 

Prophase, Metaphase, Anaphase, and Telophase are the phases of mitosis itself. Each stage of the DNA separation procedure designates a different location. Following mitosis, a process known as cytokinesis occurs, in which the cell physically divides into two cells after separating its nuclei and other organelles in preparation for division.

 

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Types of Eukaryotic Cells

 

Animal and plant cells are both eukaryotic cells, as was already noted. Even though they initially appear to be quite different species, they share several characteristics. The existence of specialized cells with similar properties is the most significant. 

 

For instance, the outermost layer that shields the underlying structures is made up of both the epidermal cells of a plant and the skin cells of an animal.

 

Any type of specialized cell can be formed from any stem cell. These cells, which can develop into other body cells, are present in an early embryo. Stem cells are still present in modest amounts in the human body after the embryo has fully matured.

 

Meristems, which are present in the plant's roots and shoots, are where stem cells can be found. Compare the following list of plant and animal cell types. Plant cell types will be examined first, followed by animal cell types specific to cats.

 

Examples of Specialized Animal cells

 

• Skin cells: Protective outer layer.

 

• Blood cells: Transporting oxygen and being crucial for the immune system are blood cells.

 

• Muscle tissue: For power and mobility.

 

• Fat cells: A source and a place to store energy.

 

• Nerve cells: The entire body is made up of nerve cells, which transmit and receive messages to and from the brain.

 

• Reproductive cells: In order to have children, sperm and ovum (egg cells) are required.

 

Cells can frequently differentiate even more. For instance, the blood cells indicated above can separate into distinct types of white blood cells and red blood cells.

 

Examples of Specialized Plant Cells

 

• Parenchyma cells: Used for material synthesis and storage.

 

• Collenchyma cells: In young plants, shock-absorbing cells also serve as a source of support.

 

• Sclerenchyma Cells: For structural support.

 

• Xylem cells: Cells that transport water and provide structural support for plants. Water delivered by the xylem cells replaces evaporating water in the mesophyll cells (plant leaves).

 

• Phloem Cells: Transportation of nutrients by phloem cells.

 

• Reproductive cells: For the development of progeny (plants often have both male and female cells that together produce seeds).

 

• Epidermal cells: Similarly to how our skin serves as the outside, protective covering of our bodies, epidermal cells are tightly packed cells that make up the outer layer of a plant. Epidermal cells of the root region are known as root hair cells. They take in water and minerals while exchanging materials with the outer world.

 

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Differences between Eukaryotic and Prokaryotic Cells

 

• It is thought that the biggest difference between groups of organisms is the difference between the structure of prokaryotes and eukaryotes.

 

• The most important distinction is that prokaryotes' genetic material is not membrane-bound, but eukaryotes do have "real" nuclei that carry their DNA.

 

• The mitochondria and chloroplasts in eukaryotes carry out diverse metabolic functions and are thought to have originated from endosymbiotic bacteria. Similar activities take place across the cell membrane in prokaryotes; endosymbionts are incredibly uncommon.

 

• Prokaryotic cell walls often consist of a different chemical (peptidoglycan) than those of eukaryotic cells (many eukaryotes do not have a cell wall at all).

 

• Compared to eukaryotic cells, prokaryotes are typically much smaller.

 

• Eukaryotes have tightly bonded and organized chromosomes, whereas prokaryotes have only a single loop of stable chromosomal DNA that is kept in a region known as the nucleoid. 

 

Plasmids are satellite DNA structures that are present in certain eukaryotes, but they are typically thought of as a prokaryote trait because many crucial genes in prokaryotes are stored on them.

 

• Prokaryotes have a higher surface-area-to-volume ratio than Eukaryotes, which results in a higher metabolic rate, faster growth, and ultimately a shorter generation time.

 

• Prokaryotes and eukaryotes have different gene structures, packing, densities, and arrangements on chromosomes. Because prokaryotic genes lack introns and contain substantial non-coding areas between each gene, prokaryotes have extraordinarily small genomes when compared to eukaryotes.

 

The prokaryote genome is almost completely coding or controlling, whereas only about 95 percent of the human genome codes for proteins, RNA, or has a gene promoter. Additionally, unlike eukaryotes, prokaryotes express their genes together in groups called operons as opposed to individually.

 

If these genes were native to eukaryotes, they would each have their own promoter and be transcribed on their own strand of mRNA. However, in a prokaryotic cell, all genes in an operon (three in the case of the famous lac operon) are transcribed on the same piece of RNA and then made into separate proteins. The prokaryotes are simpler than eukaryotes because they have less control over how their genes are expressed.

 

Cells in eukaryotes are arranged into intricate structures by internal membranes and a cytoskeleton. The nucleus is the most recognizable membrane-bound structure.

 

Eukaryotic cells are able to perform complicated metabolic reactions that prokaryotic cells are unable to due to their ability to maintain many habitats within a single cell. In fact, a substantial portion of the reason why eukaryotic cells may swell to sizes several times greater than prokaryotic ones is due to this.