Cell membrane function and difference-digieduco

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  Functions of cell membrane : (a) The proteins and enzymes present in the cell membrane helps in the transport of certain substances like sugar, sodium and other ions etc. across the cell membrane. (b) Cell membrane protects the internal structures of the cell and different organelles of the cytoplasm. (c) It maintains the shape of the cell. (d) It acts as a selective permeable membrane because it allows to pass certain substances while others are not, hence it helps in the transport of selective materials from and to the cells. (e) The membranes on the cytoplasmic organelles and nucleus most probably formed from the plasma membrane. (f) Other important functions of cell membrane of the cells are endocytosis and exocytosis . Endocytosis is the process by which materials are transported into the cells by the formation of vesicles. It includes two processes-phagocytosis (cell eating) and pinocytosis (cell drinking). The reverse process of endocytosis is exocytosis. During th...
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Mitochondria or Chondriosomes-digieduco

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Several protoplasmic organelles smaller than plastids are found to occur in the spaces of the ground cytoplasm-these are known as mitochondria (singular, mitochondrion) or chondriosomes (grain-like bodies), Mitochondria vary greatly in shape. Through the light microscope they appear as small granules, rods or filaments and sometimes lobed. They are about 0.5 pm in diameter and upto 6 pm in length. In living cells, mitochondria may be identified easily by means of the Janus-green B-stain. Each mitochondrion has a double layered membrane, an outer limiting one and an inner one. Such membranes are often provided with numerous granular Structures.
Mitochondria or Chondriosomes-digieduco

On the outer membrane, stalkless globose granules are present, while inner membrane bears stalked granules. The inner membrane-layer is extended forming tubular projections or microvilli, or infolded to form finger~like intrusions into the matrix called cristae (singular, crista). The matrix of a mitochondrion is mainly composed of protein. Ribosomes are present and are slightly smaller than those present in the cytoplasm. In Some regions of the matrix DNA fibrils occur. The origin of mitochondria takes place by fission of existing mitochondria (Cutter, 1978). The mitochondria, according to many authors, are proplastids. Some authors suggest that the origin of mitochondria takes place
either from the surface layer of plasma membrane or from the endoplasmic reticulum.Mitochondria are present abundantly in young cells and are always formed from pre existing ones. They are produced by division and are passed on from generation to generation through the gametes. Proteins and lipids are the main chemical constituent of mitochondria ; mitochondria also contain enzymes which play important role in respiration Mitochondria contain some DNA and apparently also a small amount of RNA (Bell, 1965).

Function-Now-a-days it is believed that mitochondria are concerned With processes of energy conversion and therefore they are called the power houses of the cell. They are the locus of many enzymes in the cells, especially those of Krebs cycle, thus mitochondria
are concerned with enzyme action and respiration. 

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