Cell Biology PDF

I Functiot'ls: Lysosomes selve as intracellular digestir € !., 1 -rr.r- : : t j digestive bags' They destroy In this way they protect "'iltls. ': any foreign material which enter the ce1l suci'. r.: --:'--.:-.' ,' the cells from bacterial infection. digesting them Lysosomes also remove the worn out...

I Functiot'ls: Lysosomes selve as intracellular digestir € !., 1 -rr.r- : : t j digestive bags' They destroy In this way they protect "'iltls. ': any foreign material which enter the ce1l suci'. r.: --:'--.:-.' ,' the cells from bacterial infection. digesting them Lysosomes also remove the worn out and poorh \\ Lr:\ll- l :. ,.1:: organelles by and are also debris cell the to make way for their new replacements. In this rr'.-t,, r-'c'' -.iu'.ur\ e form a known as demolition squads, scavengers and cellular housekeepers. Thus, lysosomes kind of garbage disposal system of the cell. the During breakdown of cell structure, when the cell gets tlatt-Lagc.-1, lr-sosomes may burst and a cell' of bags suicide as eat up their own cells. Therefore, lysosomes are alsc-, kuorr-n 2. a ".ryrri", ribosome 5i.BIi&"e3qffidrii** Nature and occurrence. The mitochondria (singular: mitochondrion) are tiny bodies of varying shapes (cylindrical, rod-shaped, spherical) and size (0.2 mm to 2 mm), distributed in the cytoplasm. Each mitochondrion is bounded by a double membrane envelope. Outer membrane is porous. The inner membrane is thrown into folds and, therefore, have an area several times the surface of area of the outer membrane (Figure 34)' These folds are cailed cristae and are studded (dotted) with sma1l rounded bodies known as F, particles or oxysomes. The interior cavity of the mitochondria is filled with a proteinaceous (gel-like) matrix which contains a few smali-sized ribosomes, a circular DNA molecule and phosphate granules. Mitochondria are absent in bacteria and the j4,..\. i.: |.}.. inner membrane outer chamber matrix in inner chamber I '*ir-l ilNA molecule :igure 34. A longitudinally cut mitochondrion showing its internal structure. re m%tudygil red blood cells of mammals. +. outer membrane... Mitochondria are sites of cellular respiration. They use molecular oxygen from air to oxidise the carbohydrates and fats (lipids) present in the cell to carbon dioxide and water vapour. Oxidation releases energy, a portion of which is used to form ATP (adenosine triphosphate). Since the mitochondria synthesize, energy-rich compounds (ATP), they known as 'power house' of the ceil. The energv stored in ATP is used by the celi. ATp stands for the organic CollpoLulrl.r,-lenosine triphosphate. ATP is generally known as energy carrier or enerfv- currencv of the cell 1t is a common cellular htel, i.e., it is used to drive numerous energ\--requirinS prc.es>es.-: th. ce-1 ihe boclr' of an organism uses the energy stored in ATP for" 1. synthesis of chemical compounds. ; DNA replication, transcription of nXAt, and synthesisI of proteurs, carbrl--.;:.::.. ::.:.--:-:s.r.ntl 2. mechanical work, such as contraction of muscles (forq,' movement, locor-r.r..:- - r- i;. ,-... rr-.rr\-€111€rlt of cilia and flagella, conduction of nerve impulse and*" L productionoiheat.-e:.:-. :'. = tc:riC eel), andlight (e.g., fireflies). Mitochondria are a'i:ie : -- -r' ,::.: organelles. 36 r.r,ni.L. r',i tl-reir own proteins; so, they are regaided as semiautonomous The Funcomentol Unit of Life: Cell u I