CHAPTER 2

CHAPTER 2 STRUCTURE OF CELLS AND ORGANELLESMICROBODIESCENTRIOLESCILIA, FLAGELLA

MICROBODIES

STRUCTURE~ small spherical membrane-bounded bodies 0.5-1.5 micrometer(10^-6m) in diameter.~ a crystalline structure inside a sac which also contains amorphous gray material.~ bound by a single membrane that separates their content from the cytosol (the internal fluid of cell) and contain membrane protein critical for various functionFUNCTIONSThey participate in the metabolism of fatty acids and many other metabolites. E.g. Peroxisome contain oxidative enzymes, for example catalase which breakdown toxic hydrogen peroxide into water and oxygen.Import proteins into the organelles and aid in proliferation. E.g. Peroxisome can replicate by enlarging and then dividing.Peroxisome also take part in the production of bile acid and proteins.Glyoxysomes are found in the fat storage tissue of germinating seedlings such as those of peanut plants. Glyoxysomes contain enzymes that catalyze the conversion of fat and oil into sugars until the germinating seedlings can produce their own sugars through photosynthesis.

CENTRIOLESSTRUCTURECentrioles are found in animal cellsCentrioles are located outside the nucleus in a material of poorly defined structure call the centrosomeCentrioles are paired cylinders (about 0.3-0.5 micrometer long and 0.24 micrometer in diameter) and held at right angles to each other.

Each cylinders consists of nine microtubules in a 9+0 arrangement

Centrioles have no central microtubule.

FUNCTIONSAct as organizers of spindle fibres and are involved in the separation of chromosomes or chromatids during cell division

Centrioles during cell divisionIn some cells, centrioles divide to produce basal bodies from which flagella and cilia develop (ciliogenesis)

FLAGELLA AND CILIASTRUCTUREFlagella and cilia are organelles with one end projecting out of the cell and the other end connected to a basal body below the plasma membrane. Flagella of prokaryotes contain the protein flagellin.Flagella and cilia of eukaryotes have the same basic structure, with 9+2 arrangement of microtubules. Flagella are longer and occur singly or in small numbers whereas cilia are shorter and occur in large numbers.

Refer to pg 85 Sasbadi

FUNCTIONImportant in cell motility. For example, flagellum in unicellular organisms Euglena sp. and Clamydomonas sp.To acquire food. For example, feeding current generated by cilia in paramecium sp.To propel fluids. For example, cilia lining the respiratory tract to move mucus and trapped particles.

LETS TAKE A QUIZ !!!Bacterial flagella is made up of TubulinDynienFlagellinVimetin

Which of the followings are the functions of cilia and flagella? 1 locomotion 2 body defense 3 excretion 4 all of these

The arrangement of microtubules in eukaryotic flagella is referred to as ..Which of the following are the features differentiates cilia and flagella? 1 cilia are shorter than flagella 2 flagella are lesser in numbers compare to cilia 3 cilia is distributed throughout the cell surface 4 all of theseIn eukaryotic flagella, the arrangement of microtubule is ?

1 ) 9+4 2) 9+3 3) 9+0 4) 9+2ANSWERSFlagellinAll of these9+2All of these9+2