The cytoplasm is the solution within the cell membrane. It contains enzymes for both aerobic and anaerobic glycolysis and other metabolic reactions, together with sugars, salts, amino acids, nucleotides and everything essential for efficient cell function.
A Mitochondrion is a rod-shaped organelle and is where aerobic respiration takes place in all eukaryotic cells. Mitochondria are surrounded by a double membrane: the outer membrane is simple and quite permeable, while the inner membrane is highly folded into cristae, which increases the surface area thereby promoting the attachment of enzymes, electron carrier molecules and other proteins involved in the Krebs cycle and the electron transport chain. The space enclosed by the inner membrane is called the mitochondrial matrix, and contains small circular strands of DNA. The inner membrane is covered with stalked particles, which are the site of ATP synthesis and further increase the surface area of the mitochondrion. The structure of mitochondria varies between cell types. In a metabolically active cell such as the liver the mitochondria are larger and more numerous and the cristae are more prominent than would be in a fat cell.
Ribosomes are the smallest and most numerous of the cell organelles and are the sites of protein synthesis. They are composed of protein and RNA and are manufactured in the nucleolus of the nucleus. Ribosomes are either found free in the cytoplasm, where they make proteins for the cell’s own use, or they are found attached to rough endoplasmic reticulum, where they make proteins for export from the cell. Ribosomes are often found in groups called Polysomes. All eukaryotic ribosomes are of the larger “8OS” type.
Smooth Endoplasmic Reticulum (SER) is a series of membrane channels involved in synthesising and transporting materials, mainly lipids, needed by the cell. Rough Endoplasmic Reticulum is similar to SER, but the membrane is covered with numerous ribosomes. The ribosomes synthesis proteins, which are processed in the Rough Endoplasmic Reticulum by enzymatically modifying the polypeptide chain, or adding carbohydrates, before being exported from the cell via the Golgi Body.
The Golgi apparatus is another series of flattened membrane vesicles formed from the endoplasmic reticulum. Its function is to transport proteins from the rough endoplasmic reticulum to the cell membrane for export. Parts of the rough endoplasmic reticulum containing proteins fuse with one side of the Golgi body membranes, while at the other side small vesicles bud off and move towards the cell membrane, where they fuse, eleasing their contents by exocytosis.
Lysosomes are small membrane-bound vesicles formed from the Rough endoplasmic reticulum containing numerous digestive enzymes. They are used to breakdown unwanted chemicals, toxins, organelles or even whole cells so that the materials may be recycled. They can also fuse with a feeding vacuole to digest its contents.
The Cytoskeleton is a network of protein fibres extending throughout all eukaryotic cells, used for support, transport and motility. The cytoskeleton is attached to the cell membrane and gives the cell its shape, as well as holding all the organelles in position. There are three types of protein fibres: microfilaments, intermediate filaments and microtubules. Each protein filament has a corresponding motor protein that can move along the fibre carrying substances such as organelles, chromosomes or other cytoskeleton fibres. Such motor proteins are responsible for the movement of chromosomes in mitosis, the process of cytokinesis in cell division and even muscle contractions in animals.
The Centrioles are a pair of short microtubules involved in cell division. Before each division the centriole replicates itself and the two centrioles move to opposite poles of the cell, where they initiate the spindle that organises and separates the chromosomes.
Microvilli are small, finger-like extensions of the cell membrane found in certain cells such as in the epithelial cells of the intestine and kidney, where they increase the surface area for absorption of materials. Microvilli are well-adapted to the function of absorption due to their rich supply of blood vessels which allows a steep concentration gradient to be maintained. Microvilli are particularly important in the process of glucose absorption, which eventually provides the cells with metabolic energy for survival.
In Conclusion, the structure of the mammalian cell and the organelles it contains has evolved to become highly specialised and adapted to a particular function. The differing functions of each cell and each organelle means that cells are dependent upon each other to provide substances and carry out functions which other cells can no longer perform due to the process of differentiation. However, this allows body systems to work efficiently, aiding survival.
by
katehanshaw (student)
