Biology XI: 8 Cell d unit of Life(4 Semi Autonomous Cell Organelles

Semi Autonomous Cell Organelles & Mitochondria and Chloroplast Mitochondria Sausage-shaped or cylindrical cell organelles, visible only with specific staining under the microscope Have double-membrane system: Inner membrane and Outer membrane These membranes divide the lumen of the mitochondria into two compartments − the outer compartment and the inner compartment (matrix) Outer membrane − forms the boundary of the organelle Inner membrane − forms the infoldings called cristae; this increases the surface area of the inner membrane Both membranes have specific enzymes associated with them. Importance: Mitochondria are called the ‘power houses of cells’ since they are the site for aerobic respiration, and form ATP (source of cellular energy). Matrix contains components like the single circular DNA, RNA, ribosomes (70s) and the components needed for protein synthesis. Mitochondria divide by fission. Plastids Found in plant cells and euglenoids Bear pigments and impart colours to plants Large-sized, and hence, easily observable Chloroplast Location: Mesophyll cells in leaves Can be variable in shape (oval/spherical/discoid/ribbon-like), in length and in number (1 per cell in Chamydomonas to 20−40 per cell in green algae) Have double membrane: Outer membrane and Inner membrane (less permeable) Stroma: Space enclosed by the inner membrane; contains enzymes required for carbohydrate and protein syntheses Thylakoids: Flattened, membrane-bound sacs present in the stroma; contains chlorophyll pigment Grana: Integrated thyllakoids; like piles of coins, where thyllakoids are arranged in stacks Stroma Lamella: Flat, membrane-bound tubules; connect thylakoids present in the different grana Lumen: Space present in thylakoid, i.e., the space enclosed by the thylakoid membrane Stroma of the chloroplast has small, circular DNA and ribosomes (70s).