The Structure of a Eukaryotic Cell

••• Eukaryotic Cell (US Government Photo)

The eukaryotic cell definition is any cell containing a well-defined, membrane-bound nucleus, which differentiates it from a prokaryotic cell that does not possess a well-defined nucleus. A eukaryotic cell structure also shows presence of membrane-bound cell structures called organelles that carry out different functions of the cell.

Apart from the nucleus, eukaryotic cells contain organelles such as mitochondria, Golgi apparatus, endoplasmic reticulum and, in the case of plant cells, chloroplasts.

A eukaryotic cell functions like an individual unit, with its cell organelles carrying out various functions of the cell such as homeostasis, protein synthesis and energy generation.

Cell Wall

A cell wall is an external rigid structure made of cellulose present mainly in plant cells and in some species of bacteria, fungi and algae.

The cellulose structure of a cell wall provides structure and stiffness to the cell and also protects it against physical injury.

Plasma Membrane

Eukaryotic cells have a thin sheath called a plasma membrane that separates the cell from the external environment. The membrane is made up of a double layer of lipids and is embedded with protein molecules.

The plasma membrane protects its cell contents and regulates the organic matter that passes through the cell. It allows certain molecules such as oxygen, water and certain ions to pass into the cell and expels waste products from the cell.

Nucleus and DNA

All the genetic material of an organism is contained in the nucleus of a eukaryotic cell. DNA, which is a tightly coiled strand, is enclosed inside the nuclear envelope, the outer membrane of the nucleus.

The DNA of an organism contains information regarding the entire genetic makeup of that organism. The nucleus gives instructions related to cell functions that are carried out by different organelles.

Mitochondria and Energy

All cells require energy, and they generate energy in their mitochondria. Mitochondria are the respiratory centers of a cell with each eukaryotic cell having up to 2,000 mitochondria. Each mitochondrion has an outer lipid layer and a coiled inner layer called a cristae, where respiratory oxidation takes place.

Mitochondria generate energy in the form of adenosine triphosphate (ATP) by oxidizing carbohydrates, such as glucose, in the cell. Organisms can utilize energy in the form of ATP. Since mitochondria generate ATP, they are known as the powerhouse of a cell.

Endoplasmic Reticulum

In a eukaryotic cell structure, the nuclear envelope is often connected to a long winding structure called endoplasmic reticulum (ER) that appears like a stack of discs. There are two types of ER, rough ER and smooth ER.

Rough ER is named so because of its undulating appearance caused by the presence of small round organelles called ribosomes on its surface. Coding of proteins in the form of amino acid chains takes place in ribosomes. Therefore, rough ER usually produces proteins whereas smooth ER lacks ribosomes and produces fats.

Golgi Apparatus

One of the functions of a eukaryotic cell is protein synthesis. A Golgi apparatus is a disc-like structure usually located near endoplasmic reticulum. This organelle was first discovered by Camillio Golgi, after whom it is named.

The Golgi apparatus receives proteins synthesized by the endoplasmic reticulum and sorts and packs it into protein packages.

Lysosomes and Waste

All cell organelles produce waste matter while performing their functions. This waste matter gets collected in lysosomes, which are sac-like structures containing digestive enzymes.

Lysosomes break down waste matter, dead organelles and foreign particles through a process called autolysis and are, therefore, called the suicidal sacs of a cell.

Chloroplast and Chlorophyll

Just like a cell wall, a chloroplast is an organelle found in eukaryotic cells of plants, algae and some species of fungi.

Chloroplasts contain molecules of chlorophyll pigment necessary for photosynthesis. Solar energy from the sun is utilized in chloroplasts to activate photosynthesis.

References

About the Author

Kavita Naik is a freelance writer and instructional designer. She holds Bachelor of Science in Zoology. She has edited life science research papers for several major scientific journals. She has years of experience in designing and developing learning solutions for educational as well as professional purposes. She has also created Common Core-compliant curriculum.

Photo Credits

  • Eukaryotic Cell (US Government Photo)

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