Margaret Walsh South University Online
Eukaryotic organelles Living things have evolved into three categories of closely related organisms, called "domains": Archaea, Bacteria, and Eukaryota. Life as we see it each day — including plants and animals — belongs to the third domain, Eukaryota. Eukaryotic cells are a more complex opposed to prokaryotes (simpler based cells), and the DNA is linear and found within a nucleus. Organelles are small structures within cells that perform specialized functions. They are found within the cytoplasm (a semiliquid substance that composes the foundation of a cell) Just as the name indicates, you can think of organelles as small organs. There are a dozen different types of organelles commonly found in eukaryotic cells. Some structures of organelles are membrane bound. The Plasma Membrane is a membrane boundary of a cell, and sorts cell transport and is the outermost cell surface. It separates the cell from the external environment. The plasma membrane is made mostly of proteins and lipids, especially phospholipids. The lipids occur in two layers (a bilayer). Proteins embedded in the bilayer appear to float within the lipid, so the membrane is constantly in flux. The membrane is therefore referred to as a fluid mosaic structure. Within the fluid mosaic structure, proteins carry out most of the membrane's functions (prokaryote and eukaryote cell structure, 2000.). The nucleus of eukaryotic cells is composed primarily of protein and deoxyribonucleic acid, or DNA. The DNA is organized into linear units called chromosomes. Functional segments of the chromosomes are referred to as genes. Approximately 100,000 genes are located in the nucleus of all human cells. Within the nucleus are two or more dense organelles referred to as nucleoli. In nucleoli, submicroscopic particles known as ribosomes are put together before their passage out of the nucleus into the cytoplasm. The endoplasmic reticulum (ER) is an organelle that is a series of membranes extending throughout the cytoplasm of eukaryotic cells. In some places, the ER is studded with submicroscopic bodies called ribosomes. The endoplasmic reticulum (ER) consists of two types - the rough endoplasmic reticulum and the smooth endoplasmic reticulum. This type of ER is referred to as rough ER. In other places, there are no ribosomes. This type of ER is called smooth ER. The ER is the site of protein synthesis in a cell. Within the ribosomes, amino acids are actually bound together to form proteins. We can take a look at another organelle called the Golgi body (also called the Golgi apparatus). The Golgi body is a series of flattened sacs, usually curled at the edges. In the Golgi body, the cell's proteins and lipids are processed and packaged before being sent to their final destination (prokaryotic and eukaryotic cell structure, 2000.). Lysosomes and vacuoles are membranous sacs. The lysosome is derived from the Golgi body. It is a drop like sac of enzymes in the cytoplasm. These enzymes are used for digestion within the cell. They break down particles of food taken into the cell and make the products available for use. In other words break down old worn-out cell parts within the cell. Vacuoles Eukaryotic cells have their own internal "power plant", called mitochondria. Mitochondria are organelles in eukaryotic cells where cellular respiration takes place. Mitochondria contain a short loop of DNA that is distinct from the DNA contained in the cell's nucleus. These tiny organelles in the cell not only produce chemical energy, but also hold the key to understanding the evolution of the eukaryotic cell. The mitochondria play a central role in making chemical energy available to the cell. Cells which...
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