Parts Of A Cell And Their Functions
Introduction to parts of a cell and their functions:
All multicellular organisms like trees, mushroom, human beings and all unicellular organisms like amoeba, paramecium are composed of eukaryotic cells. A eukaryotic cell is enclosed in within a lipid bilayer cell membrane and contains many membrane bound organelles within the cell, which performs specific functions. The separation of the organelle membranes and the interior from the rest of the cell allows organelles to perform distinct functions isolated within the separate compartments. This prevents incompatible processes from mixing together and allows stepwise processes to be more regulated and efficient. The cytoplasm is the liquid inside the cell surrounding the cell organelles.
Plasma membrane is not an organelle but is an important component of the cellular structure. The plasma membrane encloses the cell, exhibits selective permeability, and regulates the passage of materials into and out of the cell. According to the fluid mosaic model the cell membrane consists of a phospholipid layer. The lipid layer also contains phospholipids, cholesterol, and proteins which all help in the fluidity and permeability of the membrane. The proteins within the membrane allow materials to pass in and out of the cell.
Cell Organelles
Eukaryotes have specialized membrane bound structures called as organelles that carry out specific functions for the cell. The lipid bilayer membranes, which cover the organelles, also regulate and partition the flow of material in and out of these compartments.
Nucleus is one of the largest organelles of the cell. The nucleus contains the DNA genome and plays an important role in heredity. The nucleus is also the control centre, which controls and coordinates all activities of the cell like protein synthesis, secretion, cellular respiration etc.
Ribosomes are not membrane organelles and are the sites of protein synthesis. They consist of two subunits made up of rRNA and many proteins. Ribosomes are found attached to the endoplasmic reticulum or found free floating in the cytoplasm.
Endoplasmic reticulum is a network of membrane bound enclosed spaces connected at points to the nuclear membrane. There are two types of endoplasmic reticulum- the rough, which has ribosomes attached to it and the smooth, which has no ribosomes on it. The ER is responsible for the transport of proteins in cells. The smooth endoplasmic reticulum is involved in lipid synthesis and the detoxification of drugs and poisons.
Golgi apparatus is a stack of membrane-enclosed sacs. It receives vesicles and their contents from the ER and modifies proteins, packages it into vesicles and transports it to the lysosomes or the plasma membrane where it is released out of the cell through the process of exocytosis.
Lysosomes contain hydrolytic enzymes involved in intracellular digestion, degrading proteins and structures, which are worn out or not in use. They are known as the suicidal sacs of the cell because of this function.
Vacuoles are membrane bound sacs within the cell, which function in storing water and inorganic and organic molecules. Plant cell have a large central vacuole covered by a tonoplast. Animal cells have very small or no vacuoles.
Semi Autonomous Organelles
Mitochondria are cellular organelles, which are the sites of aerobic respiration and perform the function of energy production (ATP). Mitochondria are semi autonomous structures containing their own circular DNA and ribosomes, which enable them to produce their own proteins, and also self replicate through binary fission.
Chloroplasts are cell organelles which are found only in plant cells. They contain chlorophyll and are their main function is photosynthesis. They too contain their own DNA and ribosomes and exhibit the same semi autonomy as mitochondria.
by: Omkar Nayak
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