Cell Organelle
Unlike prokaryotic cells, eukaryotic cells have:
- a membrane-bound nucleus;
- numerous membrane-bound organelles—such
as the endoplasmic reticulum, Golgi apparatus,
chloroplasts, mitochondria, and others;
- several, rod-shaped chromosomes.
Because a eukaryotic cell’s nucleus is surrounded by a membrane, it is often said to have a ―true nucleus. The word organelle means ―little organ, and, organelles have specialized cellular functions, just as the organs of your body have specialized functions. Cells are the smallest units of life. They are a closed system, can self-replicate, and are the building blocks of our bodies. In order to understand how these tiny organisms work, we will look at a cell’s internal structures. We will focus on eukaryotic cells (cells that contain a nucleus).
A cell consists of two major regions, the cytoplasm and the nucleus. The nucleus is surrounded by a nuclear envelope and contains DNA in the form of chromosomes. The cytoplasm is a fluid matrix that usually surrounds the nucleus and is bound by the outer membrane of the cell. Organelles are small structures within the cytoplasm that carry out functions necessary to maintain homeostasis in the cell. They are involved in many processes, for example energy production, building proteins and secretions, destroying toxins, and responding to external signals. Organelles are considered either membranous or non-membranous. Membranous organelles possess their own plasma membrane to create a lumen separate from the cytoplasm. This may be the location of hormone synthesis or degradation of macromolecules. Non-membranous organelles are not surrounded by a plasma membrane. Most non-membranous organelles are part of the cytoskeleton, (the major support structure of the cell). These include: filaments, microtubules, and centrioles.
Ribosomes, as a site for turning RNA code into protein sequences, and chromosomes, the DNA storage complex, are examples of non-membrane organelles. These non-membranous organelles are commonly molecular complexes. They may have complex functions, but the processes by which those functions are done are usually localized to the surfaces of the complex. They neither require specific isolation nor a large working surface of membrane. Some functional parts of a eukaryote cell are types of extensions of the external membrane. They will be treated here as cell extension organelles, although they are not always called "organelles" in some biology books. The "soup" inside a cell, often so thick that it becomes a gel, has various names. In prokaryotes, its protoplasm. In eukaryotes, the material between the cell membrane and the nuclear envelope is usually called cytoplasm, which sometimes is further divided as cytosol is considered to be just outside the organelles. The material inside the nucleus is usually called nucleoplasm.
Read more about the organelles 👇
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Nucleus |
Mitochondria |
Plastids
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Endoplasmic Reticulum |
Golgi Bodies |
Lysosome |
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