Ask a Teacher

Search



: mention the all features of the structure and functions of the following cytoplasmic organelles 1.mitochondria 2.chloroplast 3.golgi appartus 4.nucleas

Mitocondria


Mitochondria are the cell's power producers. They convert energy into forms that are usable by the cell. Located in the cytoplasm, they are the sites of cellular respiration which ultimately generates fuel for the cell's activities. Mitochondria are also involved in other cell processes such as cell division and growth, as well as cell death.

Mitochondria: Distinguishing Characteristics

Mitochondria are bounded by a double membrane. Each of these membranes is a phospholipid bilayer with embedded proteins. The outermost membrane is smooth while the inner membrane has many folds. These folds are called cristae. The folds enhance the "productivity" of cellular respiration by increasing the available surface area.

The double membranes divide the mitochondrion into two distinct parts: the inter-membrane space and the mitochondrial matrix. The inter-membrane space is the narrow part between the two membranes while the mitochondrial matrix is the part enclosed by the innermost membrane. Several of the steps in cellular respiration occur in the matrix due to its high concentration of enzymes.

Mitochondria are semi-autonomous in that they are only partially dependent on the cell to replicate and grow. They have their own DNA, ribosomes and can make their own proteins. Similar to bacteria, mitochondria have circular DNA and replicate by a reproductive process called fission.


Chloroplast



Chloroplasts are the food producers of the cell. They are only found in plant cells and some protists. Animal cells do not have chloroplasts. Every green plant you see is working to convert the energy of the sun into sugars. Plants are the basis of all life on Earth. They create sugars, and the byproduct of that process is the oxygen that we breathe. That process happens in the chloroplast. Mitochondria work in the opposite direction and break down the sugars and nutrients that the cell receives.

The chloroplast comprises an aqueous matrix called stroma bound by two smooth membranes - the outer membrane and the inner membrane. Dispersed into the stroma is a network of thylakoid membranes within which chlorophyll and other photosynthetic pigments are embedded. Some of these thylakoids are present in the stacked form and are referred to as grana. The grana stacks are connected by the non-stacked domains called stroma thylakoids. The circular DNA molecules are anchored to the thylakoids. Along with these components, starch and lipid globules as well as ribosomes, enzymes and ions are present in the stroma.

Golgi Apparatus



A major organelle in most eukaryotic cells is the structure of membrane-bound sacs called the Golgi apparatus (or Golgi body, Golgi complex, dictyosome). It acts to process and package the macromolecules such as proteins and lipids that are synthesized by the cell. It has been likened to the cell's post office. A major function is the modifying, sorting and packaging of proteins for secretion. It is also involved in the transport of lipids around the cell, and the creation of lysosomes.

The sacs or folds of the Golgi apparatus are called cisternae. Typically there are five to eight cisternae but as many as sixty have been observed. The cisternae stack has five functional regions: the cis-Golgi network, cis-Golgi, medial-Golgi, trans-Golgi, and trans-Golgi network. Vesicles from the endoplasmic reticulum fuse with the cis-Golgi network and subsequently progress through the stack to the trans-Golgi network, where they are packaged and sent to the required destination. Each region contains different enzymes which selectively modify the contents depending on where they are destined to reside.

Nucleus



The nucleus is the most obvious organelle in any eukaryotic cell. It is a membrane-bound organelle and is surrounded by a double membrane. It communicates with the surrounding cytosol via numerous nuclear pores.

Within the nucleus is the DNA responsible for providing the cell with its unique characteristics. The DNA is similar in every cell of the body, but depending on the specific cell type, some genes may be turned on or off - mitotic spindlethat's why a liver cell is different from a muscle cell, and a muscle cell is different from a fat cell. When a cell is dividing, the DNA and surrounding protein condense into chromosomes  that are visible by microscopy.

The prominent structure in the nucleus is the nucleolus. The nucleolus produces ribosomes, which move out of the nucleus to positions on the rough endoplasmic reticulum where they are critical in protein synthesis.


comments powered by Disqus